工具除了会用,还应该多做点。我觉得使用一个软件工具(开源类),一般会经历几个步骤:

1. 通过wiki了解大致作用,然后开始码代码;

2. 系统性地学习其特性,找出可能需要的点,用上去;

3. 通过阅读其源码,清楚其来龙去脉;

4. 有能力你就去超越别人;

mybatis作为orm框架给我们带来了很多方便,其定制功能也让我们惊喜!还是来看看别人怎么做到的吧!

  1. 下载git仓库, https://github.com/mybatis/mybatis-3

  2. 打开IDE, 找到 test 包

  3. 进入 org.apache.ibatis.autoconstructor.AutoConstructorTest, 有一个完整的sql 样例

  1. public class AutoConstructorTest {
  2. private static SqlSessionFactory sqlSessionFactory;
  3.  
  4. @BeforeClass
  5. public static void setUp() throws Exception {
  6. // create a SqlSessionFactory
  7. try (Reader reader = Resources.getResourceAsReader("org/apache/ibatis/autoconstructor/mybatis-config.xml")) {
  8. sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
  9. }
  10.  
  11. // populate in-memory database
  12. BaseDataTest.runScript(sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(),
  13. "org/apache/ibatis/autoconstructor/CreateDB.sql");
  14. }
  15.  
  16. @Test
  17. public void fullyPopulatedSubject() {
  18. try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
  19. final AutoConstructorMapper mapper = sqlSession.getMapper(AutoConstructorMapper.class);
  20. final Object subject = mapper.getSubject(1);
  21. assertNotNull(subject);
  22. }
  23. }
  24.  
  25. @Test(expected = PersistenceException.class)
  26. public void primitiveSubjects() {
  27. try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
  28. final AutoConstructorMapper mapper = sqlSession.getMapper(AutoConstructorMapper.class);
  29. mapper.getSubjects();
  30. }
  31. }
  32.  
  33. @Test
  34. public void annotatedSubject() {
  35. try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
  36. final AutoConstructorMapper mapper = sqlSession.getMapper(AutoConstructorMapper.class);
  37. verifySubjects(mapper.getAnnotatedSubjects());
  38. }
  39. }
  40.  
  41. @Test(expected = PersistenceException.class)
  42. public void badSubject() {
  43. try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
  44. final AutoConstructorMapper mapper = sqlSession.getMapper(AutoConstructorMapper.class);
  45. mapper.getBadSubjects();
  46. }
  47. }
  48.  
  49. @Test
  50. public void extensiveSubject() {
  51. try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
  52. final AutoConstructorMapper mapper = sqlSession.getMapper(AutoConstructorMapper.class);
  53. verifySubjects(mapper.getExtensiveSubject());
  54. }
  55. }
  56.  
  57. private void verifySubjects(final List<?> subjects) {
  58. assertNotNull(subjects);
  59. Assertions.assertThat(subjects.size()).isEqualTo(3);
  60. }
  61. }

目标方法:fullyPopulatedSubject(),最终进行一条 select 查询:

  1. SELECT * FROM subject WHERE id = #{id}

首先执行的肯定 setup()方法了,setup()做了三件事:

1. 加载mybatis-config文件读取到reader中;

2. 将配置文件传递工厂builder中创建会话工厂;

3. 执行hsqldb内存数据库的初始化工作;(非本文重点)

接下来,咱们从源码的角度,主要看会话工厂的创建过程!

创建 sqlSessionFactory

  1. try (Reader reader = Resources.getResourceAsReader("org/apache/ibatis/autoconstructor/mybatis-config.xml")) {
  2. sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
  3. }
  4.  
  5. // SqlSessionFactoryBuilder.build(reader) -> XMLConfigBuilder.parse()
  6. // org.apache.ibatis.session.SqlSessionFactoryBuilder
  7. public SqlSessionFactory build(Reader reader) {
  8. return build(reader, null, null);
  9. }
  10. // 建立factory
  11. public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
  12. try {
  13. XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
  14. return build(parser.parse());
  15. } catch (Exception e) {
  16. throw ExceptionFactory.wrapException("Error building SqlSession.", e);
  17. } finally {
  18. // 加载完成后,上下文管理器重置
  19. ErrorContext.instance().reset();
  20. try {
  21. reader.close();
  22. } catch (IOException e) {
  23. // Intentionally ignore. Prefer previous error.
  24. }
  25. }
  26. }

标签解析:

  1. /**
  2. * Offline entity resolver for the MyBatis DTDs
  3. *
  4. * @author Clinton Begin
  5. * @author Eduardo Macarron
  6. */
  7. public class XMLMapperEntityResolver implements EntityResolver {
  8.  
  9. private static final String IBATIS_CONFIG_SYSTEM = "ibatis-3-config.dtd";
  10. private static final String IBATIS_MAPPER_SYSTEM = "ibatis-3-mapper.dtd";
  11. private static final String MYBATIS_CONFIG_SYSTEM = "mybatis-3-config.dtd";
  12. private static final String MYBATIS_MAPPER_SYSTEM = "mybatis-3-mapper.dtd";
  13.  
  14. private static final String MYBATIS_CONFIG_DTD = "org/apache/ibatis/builder/xml/mybatis-3-config.dtd";
  15. private static final String MYBATIS_MAPPER_DTD = "org/apache/ibatis/builder/xml/mybatis-3-mapper.dtd";
  16.  
  17. /**
  18. * Converts a public DTD into a local one
  19. *
  20. * @param publicId The public id that is what comes after "PUBLIC"
  21. * @param systemId The system id that is what comes after the public id.
  22. * @return The InputSource for the DTD
  23. *
  24. * @throws org.xml.sax.SAXException If anything goes wrong
  25. */
  26. @Override
  27. public InputSource resolveEntity(String publicId, String systemId) throws SAXException {
  28. try {
  29. if (systemId != null) {
  30. String lowerCaseSystemId = systemId.toLowerCase(Locale.ENGLISH);
  31. if (lowerCaseSystemId.contains(MYBATIS_CONFIG_SYSTEM) || lowerCaseSystemId.contains(IBATIS_CONFIG_SYSTEM)) {
  32. return getInputSource(MYBATIS_CONFIG_DTD, publicId, systemId);
  33. } else if (lowerCaseSystemId.contains(MYBATIS_MAPPER_SYSTEM) || lowerCaseSystemId.contains(IBATIS_MAPPER_SYSTEM)) {
  34. return getInputSource(MYBATIS_MAPPER_DTD, publicId, systemId);
  35. }
  36. }
  37. return null;
  38. } catch (Exception e) {
  39. throw new SAXException(e.toString());
  40. }
  41. }
  42.  
  43. private InputSource getInputSource(String path, String publicId, String systemId) {
  44. InputSource source = null;
  45. if (path != null) {
  46. try {
  47. InputStream in = Resources.getResourceAsStream(path);
  48. source = new InputSource(in);
  49. source.setPublicId(publicId);
  50. source.setSystemId(systemId);
  51. } catch (IOException e) {
  52. // ignore, null is ok
  53. }
  54. }
  55. return source;
  56. }
  57.  
  58. }

parser

  1. // org.apache.ibatis.parsing.XPathParser.XPathParser(), 设备一些必要参数
  2.  
  3. public XPathParser(Reader reader, boolean validation, Properties variables, EntityResolver entityResolver) {
  4. commonConstructor(validation, variables, entityResolver);
  5. this.document = createDocument(new InputSource(reader));
  6. }
  7. private Document createDocument(InputSource inputSource) {
  8. // important: this must only be called AFTER common constructor
  9. try {
  10. DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
  11. factory.setValidating(validation);
  12.  
  13. factory.setNamespaceAware(false);
  14. factory.setIgnoringComments(true);
  15. factory.setIgnoringElementContentWhitespace(false);
  16. factory.setCoalescing(false);
  17. factory.setExpandEntityReferences(true);
  18.  
  19. DocumentBuilder builder = factory.newDocumentBuilder();
  20. builder.setEntityResolver(entityResolver);
  21. builder.setErrorHandler(new ErrorHandler() {
  22. @Override
  23. public void error(SAXParseException exception) throws SAXException {
  24. throw exception;
  25. }
  26.  
  27. @Override
  28. public void fatalError(SAXParseException exception) throws SAXException {
  29. throw exception;
  30. }
  31.  
  32. @Override
  33. public void warning(SAXParseException exception) throws SAXException {
  34. }
  35. });
  36. return builder.parse(inputSource);
  37. } catch (Exception e) {
  38. throw new BuilderException("Error creating document instance. Cause: " + e, e);
  39. }
  40. }

// 在返回fatory的时候调用 return build(parser.parse()); 将 config.xml 的配置全部解析到 configuration 实例中

  1. // 在返回fatory的时候调用 return build(parser.parse()); 将 config.xml 的配置全部解析到 configuration 实例中
  2. // org.apache.ibatis.builder.xml.XMLConfigBuilder.parse()
  3. public Configuration parse() {
  4. if (parsed) {
  5. throw new BuilderException("Each XMLConfigBuilder can only be used once.");
  6. }
  7. parsed = true;
  8. // 根元素为 /configuration, 依次向下解析
  9. parseConfiguration(parser.evalNode("/configuration"));
  10. return configuration;
  11. }
  12.  
  13. // org.apache.ibatis.parsing.XPathParser.evalNode() 映射 xml 属性到 bean
  14. public XNode evalNode(Object root, String expression) {
  15. Node node = (Node) evaluate(expression, root, XPathConstants.NODE);
  16. if (node == null) {
  17. return null;
  18. }
  19. return new XNode(this, node, variables);
  20. }
  21.  
  22. private Object evaluate(String expression, Object root, QName returnType) {
  23. try {
  24. return xpath.evaluate(expression, root, returnType);
  25. } catch (Exception e) {
  26. throw new BuilderException("Error evaluating XPath. Cause: " + e, e);
  27. }
  28. }

具体解析项如下,从这里也一目了然,配置项支持什么:

  1. // 解析各配置参数到实例中
  2. private void parseConfiguration(XNode root) {
  3. try {
  4. //issue #117 read properties first
  5. propertiesElement(root.evalNode("properties"));
  6. Properties settings = settingsAsProperties(root.evalNode("settings"));
  7. // 这个配置没有用过吧
  8. loadCustomVfs(settings);
  9. // 解析别名设置
  10. typeAliasesElement(root.evalNode("typeAliases"));
  11. pluginElement(root.evalNode("plugins"));
  12. objectFactoryElement(root.evalNode("objectFactory"));
  13. objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
  14. reflectorFactoryElement(root.evalNode("reflectorFactory"));
  15. settingsElement(settings);
  16. // read it after objectFactory and objectWrapperFactory issue #631
  17. environmentsElement(root.evalNode("environments"));
  18. databaseIdProviderElement(root.evalNode("databaseIdProvider"));
  19. typeHandlerElement(root.evalNode("typeHandlers"));
  20. // 重要节点,解析 mapper
  21. mapperElement(root.evalNode("mappers"));
  22. } catch (Exception e) {
  23. throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
  24. }
  25. }

下面依次来看一下都怎么解析各配置项的吧~

properties 解析

  1. // propertiesElement(root.evalNode("properties")); url, resource 解析
  2. private void propertiesElement(XNode context) throws Exception {
  3. if (context != null) {
  4. Properties defaults = context.getChildrenAsProperties();
  5. String resource = context.getStringAttribute("resource");
  6. String url = context.getStringAttribute("url");
  7. if (resource != null && url != null) {
  8. throw new BuilderException("The properties element cannot specify both a URL and a resource based property file reference. Please specify one or the other.");
  9. }
  10. if (resource != null) {
  11. defaults.putAll(Resources.getResourceAsProperties(resource));
  12. } else if (url != null) {
  13. defaults.putAll(Resources.getUrlAsProperties(url));
  14. }
  15. Properties vars = configuration.getVariables();
  16. if (vars != null) {
  17. defaults.putAll(vars);
  18. }
  19. // 解析完成后,放到 parser 和 configuration 实例中
  20. parser.setVariables(defaults);
  21. configuration.setVariables(defaults);
  22. }
  23. }

settings 配置项解析,返回内容待处理

  1. // Properties settings = settingsAsProperties(root.evalNode("settings"));
  2. private Properties settingsAsProperties(XNode context) {
  3. if (context == null) {
  4. return new Properties();
  5. }
  6. Properties props = context.getChildrenAsProperties();
  7. // Check that all settings are known to the configuration class
  8. MetaClass metaConfig = MetaClass.forClass(Configuration.class, localReflectorFactory);
  9. for (Object key : props.keySet()) {
  10. if (!metaConfig.hasSetter(String.valueOf(key))) {
  11. throw new BuilderException("The setting " + key + " is not known. Make sure you spelled it correctly (case sensitive).");
  12. }
  13. }
  14. return props;
  15. }
  16.  
  17. // loadCustomVfs(settings); 这个...
  18. private void loadCustomVfs(Properties props) throws ClassNotFoundException {
  19. String value = props.getProperty("vfsImpl");
  20. if (value != null) {
  21. String[] clazzes = value.split(",");
  22. for (String clazz : clazzes) {
  23. if (!clazz.isEmpty()) {
  24. @SuppressWarnings("unchecked")
  25. Class<? extends VFS> vfsImpl = (Class<? extends VFS>)Resources.classForName(clazz);
  26. configuration.setVfsImpl(vfsImpl);
  27. }
  28. }
  29. }
  30. }

typeAliases 别名设置解析,主要做类型检查,及别名的注册工作

  1. // typeAliasesElement(root.evalNode("typeAliases"));
  2. private void typeAliasesElement(XNode parent) {
  3. if (parent != null) {
  4. for (XNode child : parent.getChildren()) {
  5. if ("package".equals(child.getName())) {
  6. // 针对package配置,需注册一系列别名,以 simpleName 代替
  7. String typeAliasPackage = child.getStringAttribute("name");
  8. configuration.getTypeAliasRegistry().registerAliases(typeAliasPackage);
  9. } else {
  10. String alias = child.getStringAttribute("alias");
  11. String type = child.getStringAttribute("type");
  12. try {
  13. Class<?> clazz = Resources.classForName(type);
  14. if (alias == null) {
  15. typeAliasRegistry.registerAlias(clazz);
  16. } else {
  17. typeAliasRegistry.registerAlias(alias, clazz);
  18. }
  19. } catch (ClassNotFoundException e) {
  20. throw new BuilderException("Error registering typeAlias for '" + alias + "'. Cause: " + e, e);
  21. }
  22. }
  23. }
  24. }
  25. }
  26. // org.apache.ibatis.type.TypeAliasRegistry.registerAlias(), 具体数据结构为 map 封装
  27. public void registerAlias(Class<?> type) {
  28. String alias = type.getSimpleName();
  29. Alias aliasAnnotation = type.getAnnotation(Alias.class);
  30. if (aliasAnnotation != null) {
  31. alias = aliasAnnotation.value();
  32. }
  33. registerAlias(alias, type);
  34. }
  35. public void registerAlias(String alias, Class<?> value) {
  36. if (alias == null) {
  37. throw new TypeException("The parameter alias cannot be null");
  38. }
  39. // issue #748
  40. String key = alias.toLowerCase(Locale.ENGLISH);
  41. if (TYPE_ALIASES.containsKey(key) && TYPE_ALIASES.get(key) != null && !TYPE_ALIASES.get(key).equals(value)) {
  42. throw new TypeException("The alias '" + alias + "' is already mapped to the value '" + TYPE_ALIASES.get(key).getName() + "'.");
  43. }
  44. TYPE_ALIASES.put(key, value);
  45. }

plugins 配置项解析,将属性注入的plugin, 添加 plugin 到 configuration

  1. // pluginElement(root.evalNode("plugins"));
  2. private void pluginElement(XNode parent) throws Exception {
  3. if (parent != null) {
  4. for (XNode child : parent.getChildren()) {
  5. String interceptor = child.getStringAttribute("interceptor");
  6. Properties properties = child.getChildrenAsProperties();
  7. // 先创建一个plugin实例,备用
  8. Interceptor interceptorInstance = (Interceptor) resolveClass(interceptor).newInstance();
  9. // 配置属性的注入,回调
  10. interceptorInstance.setProperties(properties);
  11. // 添加到 configuration
  12. configuration.addInterceptor(interceptorInstance);
  13. }
  14. }
  15. }
  16. public class InterceptorChain {
  17.  
  18. private final List<Interceptor> interceptors = new ArrayList<>();
  19.  
  20. public Object pluginAll(Object target) {
  21. for (Interceptor interceptor : interceptors) {
  22. target = interceptor.plugin(target);
  23. }
  24. return target;
  25. }
  26.  
  27. public void addInterceptor(Interceptor interceptor) {
  28. interceptors.add(interceptor);
  29. }
  30.  
  31. public List<Interceptor> getInterceptors() {
  32. return Collections.unmodifiableList(interceptors);
  33. }
  34.  
  35. }

objectFactory 配置项解析,与plugin原理相似,做替换自定义作用

  1. // objectFactoryElement(root.evalNode("objectFactory"));
  2. private void objectFactoryElement(XNode context) throws Exception {
  3. if (context != null) {
  4. String type = context.getStringAttribute("type");
  5. Properties properties = context.getChildrenAsProperties();
  6. ObjectFactory factory = (ObjectFactory) resolveClass(type).newInstance();
  7. factory.setProperties(properties);
  8. configuration.setObjectFactory(factory);
  9. }
  10. }
  11.  
  12. // objectWrapperFactoryElement(root.evalNode("objectWrapperFactory")); 没什么特别
  13. private void objectWrapperFactoryElement(XNode context) throws Exception {
  14. if (context != null) {
  15. String type = context.getStringAttribute("type");
  16. ObjectWrapperFactory factory = (ObjectWrapperFactory) resolveClass(type).newInstance();
  17. configuration.setObjectWrapperFactory(factory);
  18. }
  19. }
  1. // reflectorFactoryElement(root.evalNode("reflectorFactory"));
  2. private void reflectorFactoryElement(XNode context) throws Exception {
  3. if (context != null) {
  4. String type = context.getStringAttribute("type");
  5. ReflectorFactory factory = (ReflectorFactory) resolveClass(type).newInstance();
  6. configuration.setReflectorFactory(factory);
  7. }
  8. }

settings 选项解析,设置各种开关, 如缓存

  1. // settingsElement(settings); 设置各种开关, 如缓存
  2. private void settingsElement(Properties props) throws Exception {
  3. configuration.setAutoMappingBehavior(AutoMappingBehavior.valueOf(props.getProperty("autoMappingBehavior", "PARTIAL")));
  4. configuration.setAutoMappingUnknownColumnBehavior(AutoMappingUnknownColumnBehavior.valueOf(props.getProperty("autoMappingUnknownColumnBehavior", "NONE")));
  5. configuration.setCacheEnabled(booleanValueOf(props.getProperty("cacheEnabled"), true));
  6. configuration.setProxyFactory((ProxyFactory) createInstance(props.getProperty("proxyFactory")));
  7. configuration.setLazyLoadingEnabled(booleanValueOf(props.getProperty("lazyLoadingEnabled"), false));
  8. configuration.setAggressiveLazyLoading(booleanValueOf(props.getProperty("aggressiveLazyLoading"), false));
  9. configuration.setMultipleResultSetsEnabled(booleanValueOf(props.getProperty("multipleResultSetsEnabled"), true));
  10. configuration.setUseColumnLabel(booleanValueOf(props.getProperty("useColumnLabel"), true));
  11. configuration.setUseGeneratedKeys(booleanValueOf(props.getProperty("useGeneratedKeys"), false));
  12. configuration.setDefaultExecutorType(ExecutorType.valueOf(props.getProperty("defaultExecutorType", "SIMPLE")));
  13. configuration.setDefaultStatementTimeout(integerValueOf(props.getProperty("defaultStatementTimeout"), null));
  14. configuration.setDefaultFetchSize(integerValueOf(props.getProperty("defaultFetchSize"), null));
  15. configuration.setMapUnderscoreToCamelCase(booleanValueOf(props.getProperty("mapUnderscoreToCamelCase"), false));
  16. configuration.setSafeRowBoundsEnabled(booleanValueOf(props.getProperty("safeRowBoundsEnabled"), false));
  17. configuration.setLocalCacheScope(LocalCacheScope.valueOf(props.getProperty("localCacheScope", "SESSION")));
  18. configuration.setJdbcTypeForNull(JdbcType.valueOf(props.getProperty("jdbcTypeForNull", "OTHER")));
  19. configuration.setLazyLoadTriggerMethods(stringSetValueOf(props.getProperty("lazyLoadTriggerMethods"), "equals,clone,hashCode,toString"));
  20. configuration.setSafeResultHandlerEnabled(booleanValueOf(props.getProperty("safeResultHandlerEnabled"), true));
  21. configuration.setDefaultScriptingLanguage(resolveClass(props.getProperty("defaultScriptingLanguage")));
  22. @SuppressWarnings("unchecked")
  23. Class<? extends TypeHandler> typeHandler = (Class<? extends TypeHandler>)resolveClass(props.getProperty("defaultEnumTypeHandler"));
  24. configuration.setDefaultEnumTypeHandler(typeHandler);
  25. configuration.setCallSettersOnNulls(booleanValueOf(props.getProperty("callSettersOnNulls"), false));
  26. configuration.setUseActualParamName(booleanValueOf(props.getProperty("useActualParamName"), true));
  27. configuration.setReturnInstanceForEmptyRow(booleanValueOf(props.getProperty("returnInstanceForEmptyRow"), false));
  28. configuration.setLogPrefix(props.getProperty("logPrefix"));
  29. @SuppressWarnings("unchecked")
  30. Class<? extends Log> logImpl = (Class<? extends Log>)resolveClass(props.getProperty("logImpl"));
  31. configuration.setLogImpl(logImpl);
  32. configuration.setConfigurationFactory(resolveClass(props.getProperty("configurationFactory")));
  33. }

environments 环境配置设置,根据指定环境,获取相应配置,加载数据源配置

  1. // environmentsElement(root.evalNode("environments")); 环境配置
  2. private void environmentsElement(XNode context) throws Exception {
  3. if (context != null) {
  4. if (environment == null) {
  5. // 默认为 development
  6. environment = context.getStringAttribute("default");
  7. }
  8. for (XNode child : context.getChildren()) {
  9. String id = child.getStringAttribute("id");
  10. // 查找当前环境配置,指定加载
  11. if (isSpecifiedEnvironment(id)) {
  12. // 事务管理、数据源
  13. TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));
  14. DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));
  15. DataSource dataSource = dsFactory.getDataSource();
  16. Environment.Builder environmentBuilder = new Environment.Builder(id)
  17. .transactionFactory(txFactory)
  18. .dataSource(dataSource);
  19. configuration.setEnvironment(environmentBuilder.build());
  20. }
  21. }
  22. }
  23. }
  24. // 环境配置包含, id, 事务管理, 数据源
  25. public Environment build() {
  26. return new Environment(this.id, this.transactionFactory, this.dataSource);
  27. }

databaseIdProvider 解析,对多数据源,包含多 机器,或多类型数据库 mysql,sqlserver

  1. // databaseIdProviderElement(root.evalNode("databaseIdProvider"));
  2. private void databaseIdProviderElement(XNode context) throws Exception {
  3. DatabaseIdProvider databaseIdProvider = null;
  4. if (context != null) {
  5. String type = context.getStringAttribute("type");
  6. // awful patch to keep backward compatibility
  7. if ("VENDOR".equals(type)) {
  8. type = "DB_VENDOR";
  9. }
  10. Properties properties = context.getChildrenAsProperties();
  11. databaseIdProvider = (DatabaseIdProvider) resolveClass(type).newInstance();
  12. databaseIdProvider.setProperties(properties);
  13. }
  14. Environment environment = configuration.getEnvironment();
  15. if (environment != null && databaseIdProvider != null) {
  16. String databaseId = databaseIdProvider.getDatabaseId(environment.getDataSource());
  17. configuration.setDatabaseId(databaseId);
  18. }
  19. }

自定义 typeHandler

  1. // typeHandlerElement(root.evalNode("typeHandlers")); 自定义 typeHandler
  2. private void typeHandlerElement(XNode parent) throws Exception {
  3. if (parent != null) {
  4. for (XNode child : parent.getChildren()) {
  5. if ("package".equals(child.getName())) {
  6. String typeHandlerPackage = child.getStringAttribute("name");
  7. typeHandlerRegistry.register(typeHandlerPackage);
  8. } else {
  9. String javaTypeName = child.getStringAttribute("javaType");
  10. String jdbcTypeName = child.getStringAttribute("jdbcType");
  11. String handlerTypeName = child.getStringAttribute("handler");
  12. Class<?> javaTypeClass = resolveClass(javaTypeName);
  13. JdbcType jdbcType = resolveJdbcType(jdbcTypeName);
  14. Class<?> typeHandlerClass = resolveClass(handlerTypeName);
  15. if (javaTypeClass != null) {
  16. if (jdbcType == null) {
  17. typeHandlerRegistry.register(javaTypeClass, typeHandlerClass);
  18. } else {
  19. typeHandlerRegistry.register(javaTypeClass, jdbcType, typeHandlerClass);
  20. }
  21. } else {
  22. typeHandlerRegistry.register(typeHandlerClass);
  23. }
  24. }
  25. }
  26. }
  27. }
  28. // org.apache.ibatis.type.TypeHandlerRegistry.register(), 以map保存映射
  29. private void register(Type javaType, JdbcType jdbcType, TypeHandler<?> handler) {
  30. if (javaType != null) {
  31. Map<JdbcType, TypeHandler<?>> map = TYPE_HANDLER_MAP.get(javaType);
  32. if (map == null || map == NULL_TYPE_HANDLER_MAP) {
  33. map = new HashMap<>();
  34. TYPE_HANDLER_MAP.put(javaType, map);
  35. }
  36. map.put(jdbcType, handler);
  37. }
  38. ALL_TYPE_HANDLERS_MAP.put(handler.getClass(), handler);
  39. }

mapper 解析,crud

  1. // mapperElement(root.evalNode("mappers"));
  2. private void mapperElement(XNode parent) throws Exception {
  3. if (parent != null) {
  4. for (XNode child : parent.getChildren()) {
  5. if ("package".equals(child.getName())) {
  6. String mapperPackage = child.getStringAttribute("name");
  7. configuration.addMappers(mapperPackage);
  8. } else {
  9. String resource = child.getStringAttribute("resource");
  10. String url = child.getStringAttribute("url");
  11. String mapperClass = child.getStringAttribute("class");
  12. if (resource != null && url == null && mapperClass == null) {
  13. ErrorContext.instance().resource(resource);
  14. InputStream inputStream = Resources.getResourceAsStream(resource);
  15. XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
  16. mapperParser.parse();
  17. } else if (resource == null && url != null && mapperClass == null) {
  18. ErrorContext.instance().resource(url);
  19. InputStream inputStream = Resources.getUrlAsStream(url);
  20. XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
  21. mapperParser.parse();
  22. } else if (resource == null && url == null && mapperClass != null) {
  23. Class<?> mapperInterface = Resources.classForName(mapperClass);
  24. configuration.addMapper(mapperInterface);
  25. } else {
  26. throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
  27. }
  28. }
  29. }
  30. }
  31. }

mapper解析细节

  1. // org.apache.ibatis.builder.xml.XMLMapperBuilder.parse() mapper解析细节
  2. public void parse() {
  3. // 只解析一次 namespace
  4. if (!configuration.isResourceLoaded(resource)) {
  5. configurationElement(parser.evalNode("/mapper"));
  6. configuration.addLoadedResource(resource);
  7. bindMapperForNamespace();
  8. }
  9.  
  10. // 解析 resultMaps
  11. parsePendingResultMaps();
  12. parsePendingCacheRefs();
  13. parsePendingStatements();
  14. }
  15. private void configurationElement(XNode context) {
  16. try {
  17. String namespace = context.getStringAttribute("namespace");
  18. if (namespace == null || namespace.equals("")) {
  19. throw new BuilderException("Mapper's namespace cannot be empty");
  20. }
  21. builderAssistant.setCurrentNamespace(namespace);
  22. cacheRefElement(context.evalNode("cache-ref"));
  23. cacheElement(context.evalNode("cache"));
  24. parameterMapElement(context.evalNodes("/mapper/parameterMap"));
  25. resultMapElements(context.evalNodes("/mapper/resultMap"));
  26. sqlElement(context.evalNodes("/mapper/sql"));
  27. buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
  28. } catch (Exception e) {
  29. throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
  30. }
  31. }
  32.  
  33. private void parsePendingResultMaps() {
  34. Collection<ResultMapResolver> incompleteResultMaps = configuration.getIncompleteResultMaps();
  35. synchronized (incompleteResultMaps) {
  36. Iterator<ResultMapResolver> iter = incompleteResultMaps.iterator();
  37. while (iter.hasNext()) {
  38. try {
  39. iter.next().resolve();
  40. iter.remove();
  41. } catch (IncompleteElementException e) {
  42. // ResultMap is still missing a resource...
  43. }
  44. }
  45. }
  46. }
  47.  
  48. private void parsePendingCacheRefs() {
  49. Collection<CacheRefResolver> incompleteCacheRefs = configuration.getIncompleteCacheRefs();
  50. synchronized (incompleteCacheRefs) {
  51. Iterator<CacheRefResolver> iter = incompleteCacheRefs.iterator();
  52. while (iter.hasNext()) {
  53. try {
  54. iter.next().resolveCacheRef();
  55. iter.remove();
  56. } catch (IncompleteElementException e) {
  57. // Cache ref is still missing a resource...
  58. }
  59. }
  60. }
  61. }
  62.  
  63. private void parsePendingStatements() {
  64. Collection<XMLStatementBuilder> incompleteStatements = configuration.getIncompleteStatements();
  65. synchronized (incompleteStatements) {
  66. Iterator<XMLStatementBuilder> iter = incompleteStatements.iterator();
  67. while (iter.hasNext()) {
  68. try {
  69. iter.next().parseStatementNode();
  70. iter.remove();
  71. } catch (IncompleteElementException e) {
  72. // Statement is still missing a resource...
  73. }
  74. }
  75. }
  76. }

// 最后,返回一个 DefaultSqlSessionFactory, 载入配置项

  1. public SqlSessionFactory build(Configuration config) {
  2. return new DefaultSqlSessionFactory(config);
  3. }

// 会话创建好后,可以执行sql了

  1. public void fullyPopulatedSubject() {
  2. // 打开一个连接,使用完成后关闭
  3. try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
  4. final AutoConstructorMapper mapper = sqlSession.getMapper(AutoConstructorMapper.class);
  5. final Object subject = mapper.getSubject(1);
  6. assertNotNull(subject);
  7. }
  8. }

2. 打开获得一个数据库会话连接

  1. // org.apache.ibatis.session.defaults.SqlSession.openSession(); 打开一个数据库连接
  2.  
  3. @Override
  4. public SqlSession openSession() {
  5. return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, false);
  6. }
  7. private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
  8. Transaction tx = null;
  9. try {
  10. // 运行环境获取
  11. final Environment environment = configuration.getEnvironment();
  12. // 事务管理工厂获取
  13. final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
  14. // 创建新事务
  15. tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
  16. // new Executor
  17. final Executor executor = configuration.newExecutor(tx, execType);
  18. // 最后返回 DefaultSqlSession 使用
  19. return new DefaultSqlSession(configuration, executor, autoCommit);
  20. } catch (Exception e) {
  21. closeTransaction(tx); // may have fetched a connection so lets call close()
  22. throw ExceptionFactory.wrapException("Error opening session. Cause: " + e, e);
  23. } finally {
  24. // 关闭上下文监控
  25. ErrorContext.instance().reset();
  26. }
  27. }
  1. // org.apache.ibatis.session.Configuration.newExecutor()
  2. public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
  3. executorType = executorType == null ? defaultExecutorType : executorType;
  4. executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
  5. Executor executor;
  6. // 根据不同请求类型创建不同的 executor
  7. if (ExecutorType.BATCH == executorType) {
  8. executor = new BatchExecutor(this, transaction);
  9. } else if (ExecutorType.REUSE == executorType) {
  10. executor = new ReuseExecutor(this, transaction);
  11. } else {
  12. // 默认为 SIMPLE
  13. executor = new SimpleExecutor(this, transaction);
  14. }
  15. if (cacheEnabled) {
  16. // 创建缓存管理,将缓存请求委托给 executor 处理
  17. executor = new CachingExecutor(executor);
  18. }
  19. // 处理plugin 请求
  20. executor = (Executor) interceptorChain.pluginAll(executor);
  21. return executor;
  22. }
  23. // org.apache.ibatis.executor.CachingExecutor
  24. public CachingExecutor(Executor delegate) {
  25. this.delegate = delegate;
  26. delegate.setExecutorWrapper(this);
  27. }
  28.  
  29. // 最后将加载好的各种配置和实际处理,由 DefaultSqlSession 包装好后返回
  30. public DefaultSqlSession(Configuration configuration, Executor executor, boolean autoCommit) {
  31. this.configuration = configuration;
  32. this.executor = executor;
  33. this.dirty = false;
  34. this.autoCommit = autoCommit;
  35. }

3. 获取mapper,准备调用查询

  1. // org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper()
  2. @Override
  3. public <T> T getMapper(Class<T> type) {
  4. return configuration.<T>getMapper(type, this);
  5. }
  6.  
  7. // org.apache.ibatis.binding.MapperRegistry.getMapper()
  8. @SuppressWarnings("unchecked")
  9. public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
  10. // 获取 MapperProxyFactory
  11. final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
  12. if (mapperProxyFactory == null) {
  13. throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
  14. }
  15. try {
  16. // 创建 mapper 实例
  17. return mapperProxyFactory.newInstance(sqlSession);
  18. } catch (Exception e) {
  19. throw new BindingException("Error getting mapper instance. Cause: " + e, e);
  20. }
  21. }
  22.  
  23. // org.apache.ibatis.binding.newInstance();
  24. public T newInstance(SqlSession sqlSession) {
  25. final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface, methodCache);
  26. return newInstance(mapperProxy);
  27. }

4. select, 查询数据

  1. //mapper.getSubject(1); 查询数据
  2. @Override
  3. public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  4. try {
  5. if (Object.class.equals(method.getDeclaringClass())) {
  6. return method.invoke(this, args);
  7. } else if (isDefaultMethod(method)) {
  8. return invokeDefaultMethod(proxy, method, args);
  9. }
  10. } catch (Throwable t) {
  11. throw ExceptionUtil.unwrapThrowable(t);
  12. }
  13. // 加载缓存包装方法
  14. final MapperMethod mapperMethod = cachedMapperMethod(method);
  15. // 执行查询
  16. return mapperMethod.execute(sqlSession, args);
  17. }
  18.  
  19. private MapperMethod cachedMapperMethod(Method method) {
  20. return methodCache.computeIfAbsent(method, k -> new MapperMethod(mapperInterface, method, sqlSession.getConfiguration()));
  21. }
  22.  
  23. // org.apache.ibatis.binding.MapperMethod.execute(sqlSession, args); 针对不同类型语句,做不同调用
  24. public Object execute(SqlSession sqlSession, Object[] args) {
  25. Object result;
  26. switch (command.getType()) {
  27. case INSERT: {
  28. Object param = method.convertArgsToSqlCommandParam(args);
  29. result = rowCountResult(sqlSession.insert(command.getName(), param));
  30. break;
  31. }
  32. case UPDATE: {
  33. Object param = method.convertArgsToSqlCommandParam(args);
  34. result = rowCountResult(sqlSession.update(command.getName(), param));
  35. break;
  36. }
  37. case DELETE: {
  38. Object param = method.convertArgsToSqlCommandParam(args);
  39. result = rowCountResult(sqlSession.delete(command.getName(), param));
  40. break;
  41. }
  42. case SELECT:
  43. if (method.returnsVoid() && method.hasResultHandler()) {
  44. executeWithResultHandler(sqlSession, args);
  45. result = null;
  46. } else if (method.returnsMany()) {
  47. result = executeForMany(sqlSession, args);
  48. } else if (method.returnsMap()) {
  49. result = executeForMap(sqlSession, args);
  50. } else if (method.returnsCursor()) {
  51. result = executeForCursor(sqlSession, args);
  52. } else {
  53. // 转换参数
  54. Object param = method.convertArgsToSqlCommandParam(args);
  55. // 执行单条查询
  56. result = sqlSession.selectOne(command.getName(), param);
  57. if (method.returnsOptional() &&
  58. (result == null || !method.getReturnType().equals(result.getClass()))) {
  59. result = Optional.ofNullable(result);
  60. }
  61. }
  62. break;
  63. case FLUSH:
  64. result = sqlSession.flushStatements();
  65. break;
  66. default:
  67. throw new BindingException("Unknown execution method for: " + command.getName());
  68. }
  69. if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
  70. throw new BindingException("Mapper method '" + command.getName()
  71. + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
  72. }
  73. return result;
  74. }
  1. // org.apache.ibatis.reflection.ParamNameResolver.getNamedParams() 返回参数,如果是单个参数,直接返回参数值
  2. // 如果是多个参数,则以 map 形式返回
  3. public Object getNamedParams(Object[] args) {
  4. final int paramCount = names.size();
  5. if (args == null || paramCount == 0) {
  6. return null;
  7. } else if (!hasParamAnnotation && paramCount == 1) {
  8. return args[names.firstKey()];
  9. } else {
  10. final Map<String, Object> param = new ParamMap<>();
  11. int i = 0;
  12. for (Map.Entry<Integer, String> entry : names.entrySet()) {
  13. param.put(entry.getValue(), args[entry.getKey()]);
  14. // add generic param names (param1, param2, ...)
  15. final String genericParamName = GENERIC_NAME_PREFIX + String.valueOf(i + 1);
  16. // ensure not to overwrite parameter named with @Param
  17. if (!names.containsValue(genericParamName)) {
  18. param.put(genericParamName, args[entry.getKey()]);
  19. }
  20. i++;
  21. }
  22. return param;
  23. }
  24. }

selectOne

  1. // org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(command.getName(), param);
  2. @Override
  3. public <T> T selectOne(String statement, Object parameter) {
  4. // Popular vote was to return null on 0 results and throw exception on too many.
  5. // 查询单条记录时,默认也是先查询list,然后取第一条
  6. List<T> list = this.<T>selectList(statement, parameter);
  7. if (list.size() == 1) {
  8. return list.get(0);
  9. } else if (list.size() > 1) {
  10. throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
  11. } else {
  12. return null;
  13. }
  14. }
  15.  
  16. // 查询列表
  17. @Override
  18. public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
  19. try {
  20. // 先获取执行语句,此处 statement 为 id
  21. MappedStatement ms = configuration.getMappedStatement(statement);
  22. return executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
  23. } catch (Exception e) {
  24. throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
  25. } finally {
  26. ErrorContext.instance().reset();
  27. }
  28. }
  29.  
  30. // org.apache.ibatis.session.Configuration.getMappedStatement(id), 获取初始化解析出来的语句
  31. public MappedStatement getMappedStatement(String id) {
  32. return this.getMappedStatement(id, true);
  33. }
  34. public MappedStatement getMappedStatement(String id, boolean validateIncompleteStatements) {
  35. if (validateIncompleteStatements) {
  36. buildAllStatements();
  37. }
  38. return mappedStatements.get(id);
  39. }

包装执行 query

  1. // executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
  2. // org.apache.ibatis.executor.CachingExecutor.query()
  3. @Override
  4. public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
  5. // 获取sql
  6. BoundSql boundSql = ms.getBoundSql(parameterObject);
  7. CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
  8. return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
  9. }
  10.  
  11. // org.apache.ibatis.mapping.MappedStatement.getBoundSql()
  12. public BoundSql getBoundSql(Object parameterObject) {
  13. BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
  14. // 字段映射
  15. List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
  16. if (parameterMappings == null || parameterMappings.isEmpty()) {
  17. boundSql = new BoundSql(configuration, boundSql.getSql(), parameterMap.getParameterMappings(), parameterObject);
  18. }
  19.  
  20. // check for nested result maps in parameter mappings (issue #30)
  21. for (ParameterMapping pm : boundSql.getParameterMappings()) {
  22. String rmId = pm.getResultMapId();
  23. if (rmId != null) {
  24. ResultMap rm = configuration.getResultMap(rmId);
  25. if (rm != null) {
  26. hasNestedResultMaps |= rm.hasNestedResultMaps();
  27. }
  28. }
  29. }
  30.  
  31. return boundSql;
  32. }
  33.  
  34. // CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
  35. // return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
  36. // org.apache.ibatis.executor.CachingExecutor.query()
  37. @Override
  38. public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
  39. throws SQLException {
  40. Cache cache = ms.getCache();
  41. if (cache != null) {
  42. flushCacheIfRequired(ms);
  43. if (ms.isUseCache() && resultHandler == null) {
  44. ensureNoOutParams(ms, boundSql);
  45. @SuppressWarnings("unchecked")
  46. List<E> list = (List<E>) tcm.getObject(cache, key);
  47. if (list == null) {
  48. list = delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
  49. tcm.putObject(cache, key, list); // issue #578 and #116
  50. }
  51. return list;
  52. }
  53. }
  54. return delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
  55. }

前面的query是一个cache的包装类,其实际查询动作需要委托给excuttor,而我们主要关心 queryFromDb 逻辑!

  1. // org.apache.ibatis.executor.SimpleExecutor.query() / BaseExecutor
  2. @SuppressWarnings("unchecked")
  3. @Override
  4. public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
  5. ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
  6. if (closed) {
  7. throw new ExecutorException("Executor was closed.");
  8. }
  9. // 缓存刷新
  10. if (queryStack == 0 && ms.isFlushCacheRequired()) {
  11. clearLocalCache();
  12. }
  13. List<E> list;
  14. try {
  15. queryStack++;
  16. list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
  17. if (list != null) {
  18. handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
  19. } else {
  20. // 没有缓存,走db
  21. list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
  22. }
  23. } finally {
  24. queryStack--;
  25. }
  26. if (queryStack == 0) {
  27. for (DeferredLoad deferredLoad : deferredLoads) {
  28. deferredLoad.load();
  29. }
  30. // issue #601
  31. deferredLoads.clear();
  32. if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
  33. // issue #482
  34. clearLocalCache();
  35. }
  36. }
  37. return list;
  38. }
  39.  
  40. // BaseExecutor
  41. private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
  42. List<E> list;
  43. // 缓存占位符
  44. localCache.putObject(key, EXECUTION_PLACEHOLDER);
  45. try {
  46. list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
  47. } finally {
  48. // 防止异常情况,保证将占位缓存删除
  49. localCache.removeObject(key);
  50. }
  51. // 操作完成后,重新放入缓存
  52. localCache.putObject(key, list);
  53. if (ms.getStatementType() == StatementType.CALLABLE) {
  54. localOutputParameterCache.putObject(key, parameter);
  55. }
  56. return list;
  57. }

执行 doQuery,主要是获取完整的 statement,使handler有据可查!

  1. @Override
  2. public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
  3. Statement stmt = null;
  4. try {
  5. // 获取全局配置
  6. Configuration configuration = ms.getConfiguration();
  7. // 获取statement, 处理 JDBC 接口
  8. StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
  9. stmt = prepareStatement(handler, ms.getStatementLog());
  10. return handler.<E>query(stmt, resultHandler);
  11. } finally {
  12. closeStatement(stmt);
  13. }
  14. }
  15. // org.apache.ibatis.session.Configuration.newStatementHandler(), 兼顾 plugins,
  16. public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
  17. StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
  18. statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
  19. return statementHandler;
  20. }

db查询

  1. // 为不同处理类型,建立不同的 handler
  2. public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
  3.  
  4. switch (ms.getStatementType()) {
  5. case STATEMENT:
  6. delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
  7. break;
  8. case PREPARED:
  9. delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
  10. break;
  11. case CALLABLE:
  12. delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
  13. break;
  14. default:
  15. throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
  16. }
  17.  
  18. }
  19.  
  20. //stmt = prepareStatement(handler, ms.getStatementLog());
  21. // org.apache.ibatis.executor.SimpleExecutor.prepareStatement(), 获取 statement, JDBC
  22. private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
  23. Statement stmt;
  24. Connection connection = getConnection(statementLog);
  25. // sql录入
  26. stmt = handler.prepare(connection, transaction.getTimeout());
  27. // 参数绑定
  28. handler.parameterize(stmt);
  29. return stmt;
  30. }
  31.  
  32. // BaseExecutor
  33. protected Connection getConnection(Log statementLog) throws SQLException {
  34. Connection connection = transaction.getConnection();
  35. if (statementLog.isDebugEnabled()) {
  36. return ConnectionLogger.newInstance(connection, statementLog, queryStack);
  37. } else {
  38. return connection;
  39. }
  40. }
  41.  
  42. // org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection()
  43. @Override
  44. public Connection getConnection() throws SQLException {
  45. if (connection == null) {
  46. // 为空时新建 connection
  47. openConnection();
  48. }
  49. return connection;
  50. }
  51.  
  52. protected void openConnection() throws SQLException {
  53. if (log.isDebugEnabled()) {
  54. log.debug("Opening JDBC Connection");
  55. }
  56. connection = dataSource.getConnection();
  57. if (level != null) {
  58. connection.setTransactionIsolation(level.getLevel());
  59. }
  60. setDesiredAutoCommit(autoCommit);
  61. }
  62.  
  63. // org.apache.ibatis.datasource.unpooled.getConnection()
  64. @Override
  65. public Connection getConnection() throws SQLException {
  66. return doGetConnection(username, password);
  67. }
  68.  
  69. private Connection doGetConnection(String username, String password) throws SQLException {
  70. Properties props = new Properties();
  71. if (driverProperties != null) {
  72. props.putAll(driverProperties);
  73. }
  74. if (username != null) {
  75. props.setProperty("user", username);
  76. }
  77. if (password != null) {
  78. props.setProperty("password", password);
  79. }
  80. return doGetConnection(props);
  81. }
  82.  
  83. private Connection doGetConnection(Properties properties) throws SQLException {
  84. // 如果没有初始化驱动,初始化
  85. initializeDriver();
  86. //
  87. Connection connection = DriverManager.getConnection(url, properties);
  88. configureConnection(connection);
  89. return connection;
  90. }
  91.  
  92. private synchronized void initializeDriver() throws SQLException {
  93. if (!registeredDrivers.containsKey(driver)) {
  94. Class<?> driverType;
  95. try {
  96. // 加载驱动
  97. if (driverClassLoader != null) {
  98. driverType = Class.forName(driver, true, driverClassLoader);
  99. } else {
  100. driverType = Resources.classForName(driver);
  101. }
  102. // DriverManager requires the driver to be loaded via the system ClassLoader.
  103. // http://www.kfu.com/~nsayer/Java/dyn-jdbc.html
  104. Driver driverInstance = (Driver)driverType.newInstance();
  105. DriverManager.registerDriver(new DriverProxy(driverInstance));
  106. registeredDrivers.put(driver, driverInstance);
  107. } catch (Exception e) {
  108. throw new SQLException("Error setting driver on UnpooledDataSource. Cause: " + e);
  109. }
  110. }
  111. }
  112.  
  113. private void configureConnection(Connection conn) throws SQLException {
  114. if (autoCommit != null && autoCommit != conn.getAutoCommit()) {
  115. conn.setAutoCommit(autoCommit);
  116. }
  117. if (defaultTransactionIsolationLevel != null) {
  118. conn.setTransactionIsolation(defaultTransactionIsolationLevel);
  119. }
  120. }
  121.  
  122. // stmt = handler.prepare(connection, transaction.getTimeout()); 组装sql
  123. // org.apache.ibatis.executor.statement.RoutingStatementHandler.prepare()
  124. @Override
  125. public Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException {
  126. return delegate.prepare(connection, transactionTimeout);
  127. }
  128.  
  129. // org.apache.ibatis.executor.statement.PreparedStatementHandler.
  130. @Override
  131. public Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException {
  132. ErrorContext.instance().sql(boundSql.getSql());
  133. Statement statement = null;
  134. try {
  135. // select * from tab where id = ?
  136. statement = instantiateStatement(connection);
  137. // 设置超时
  138. setStatementTimeout(statement, transactionTimeout);
  139. // 设置查询大小,默认不限制
  140. setFetchSize(statement);
  141. return statement;
  142. } catch (SQLException e) {
  143. closeStatement(statement);
  144. throw e;
  145. } catch (Exception e) {
  146. closeStatement(statement);
  147. throw new ExecutorException("Error preparing statement. Cause: " + e, e);
  148. }
  149. }
  150.  
  151. // 调用jdbc connection.prepareStatement(sql), 初始化语句
  152. @Override
  153. protected Statement instantiateStatement(Connection connection) throws SQLException {
  154. String sql = boundSql.getSql();
  155. if (mappedStatement.getKeyGenerator() instanceof Jdbc3KeyGenerator) {
  156. String[] keyColumnNames = mappedStatement.getKeyColumns();
  157. if (keyColumnNames == null) {
  158. return connection.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);
  159. } else {
  160. return connection.prepareStatement(sql, keyColumnNames);
  161. }
  162. } else if (mappedStatement.getResultSetType() == ResultSetType.DEFAULT) {
  163. return connection.prepareStatement(sql);
  164. } else {
  165. return connection.prepareStatement(sql, mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);
  166. }
  167. }
  168.  
  169. // PreparedStatementHandler handler.parameterize(stmt);
  170. @Override
  171. public void parameterize(Statement statement) throws SQLException {
  172. parameterHandler.setParameters((PreparedStatement) statement);
  173. }
  174.  
  175. // org.apache.ibatis.scripting.defaults.DefaultParameterHandler.setParameters()
  176. @Override
  177. public void setParameters(PreparedStatement ps) {
  178. ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
  179. List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
  180. if (parameterMappings != null) {
  181. for (int i = 0; i < parameterMappings.size(); i++) {
  182. ParameterMapping parameterMapping = parameterMappings.get(i);
  183. if (parameterMapping.getMode() != ParameterMode.OUT) {
  184. Object value;
  185. String propertyName = parameterMapping.getProperty();
  186. if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params
  187. value = boundSql.getAdditionalParameter(propertyName);
  188. } else if (parameterObject == null) {
  189. value = null;
  190. } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
  191. value = parameterObject;
  192. } else {
  193. MetaObject metaObject = configuration.newMetaObject(parameterObject);
  194. value = metaObject.getValue(propertyName);
  195. }
  196. // TypeHandler 处理参数类型
  197. TypeHandler typeHandler = parameterMapping.getTypeHandler();
  198. JdbcType jdbcType = parameterMapping.getJdbcType();
  199. if (value == null && jdbcType == null) {
  200. jdbcType = configuration.getJdbcTypeForNull();
  201. }
  202. try {
  203. typeHandler.setParameter(ps, i + 1, value, jdbcType);
  204. } catch (TypeException e) {
  205. throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);
  206. } catch (SQLException e) {
  207. throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);
  208. }
  209. }
  210. }
  211. }
  212. }
  213.  
  214. // return handler.<E>query(stmt, resultHandler);
  215. // org.apache.ibatis.executor.statement.RoutingStatementHandler.query()
  216. @Override
  217. public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
  218. return delegate.<E>query(statement, resultHandler);
  219. }
  220.  
  221. // PreparedStatementHandler.query()
  222. @Override
  223. public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
  224. PreparedStatement ps = (PreparedStatement) statement;
  225. // 调用驱动程序执行 execute
  226. ps.execute();
  227. // 处理结果集映射
  228. return resultSetHandler.<E> handleResultSets(ps);
  229. }
  230.  
  231. // org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(), 处理结果集映射
  232. @Override
  233. public List<Object> handleResultSets(Statement stmt) throws SQLException {
  234. ErrorContext.instance().activity("handling results").object(mappedStatement.getId());
  235.  
  236. final List<Object> multipleResults = new ArrayList<>();
  237.  
  238. int resultSetCount = 0;
  239. // 获取第一个结果集(开始偏移的地方)
  240. ResultSetWrapper rsw = getFirstResultSet(stmt);
  241.  
  242. List<ResultMap> resultMaps = mappedStatement.getResultMaps();
  243. int resultMapCount = resultMaps.size();
  244. validateResultMapsCount(rsw, resultMapCount);
  245. while (rsw != null && resultMapCount > resultSetCount) {
  246. ResultMap resultMap = resultMaps.get(resultSetCount);
  247. handleResultSet(rsw, resultMap, multipleResults, null);
  248. rsw = getNextResultSet(stmt);
  249. cleanUpAfterHandlingResultSet();
  250. resultSetCount++;
  251. }
  252.  
  253. String[] resultSets = mappedStatement.getResultSets();
  254. if (resultSets != null) {
  255. while (rsw != null && resultSetCount < resultSets.length) {
  256. ResultMapping parentMapping = nextResultMaps.get(resultSets[resultSetCount]);
  257. if (parentMapping != null) {
  258. String nestedResultMapId = parentMapping.getNestedResultMapId();
  259. ResultMap resultMap = configuration.getResultMap(nestedResultMapId);
  260. handleResultSet(rsw, resultMap, null, parentMapping);
  261. }
  262. rsw = getNextResultSet(stmt);
  263. cleanUpAfterHandlingResultSet();
  264. resultSetCount++;
  265. }
  266. }
  267.  
  268. return collapseSingleResultList(multipleResults);
  269. }
  270.  
  271. // org.apache.ibatis.executor.resultset.ResultSetWrapper, 根据第一行返回数据集,初始化字段名及字段类型
  272. public ResultSetWrapper(ResultSet rs, Configuration configuration) throws SQLException {
  273. super();
  274. this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
  275. this.resultSet = rs;
  276. final ResultSetMetaData metaData = rs.getMetaData();
  277. final int columnCount = metaData.getColumnCount();
  278. for (int i = 1; i <= columnCount; i++) {
  279. columnNames.add(configuration.isUseColumnLabel() ? metaData.getColumnLabel(i) : metaData.getColumnName(i));
  280. // java.sql.Types, 处理返回的类型为具体的java类型映射到 org.apache.ibatis.type.JdbcType
  281. jdbcTypes.add(JdbcType.forCode(metaData.getColumnType(i)));
  282. // java 类型全名
  283. classNames.add(metaData.getColumnClassName(i));
  284. }
  285. }

数据库结果映射到javabean

  1. // DefaultResultSetHandler.handleResultSet() 处理单条记录映射关系
  2. private void handleResultSet(ResultSetWrapper rsw, ResultMap resultMap, List<Object> multipleResults, ResultMapping parentMapping) throws SQLException {
  3. try {
  4. if (parentMapping != null) {
  5. handleRowValues(rsw, resultMap, null, RowBounds.DEFAULT, parentMapping);
  6. } else {
  7. if (resultHandler == null) {
  8. DefaultResultHandler defaultResultHandler = new DefaultResultHandler(objectFactory);
  9. handleRowValues(rsw, resultMap, defaultResultHandler, rowBounds, null);
  10. multipleResults.add(defaultResultHandler.getResultList());
  11. } else {
  12. handleRowValues(rsw, resultMap, resultHandler, rowBounds, null);
  13. }
  14. }
  15. } finally {
  16. // issue #228 (close resultsets)
  17. closeResultSet(rsw.getResultSet());
  18. }
  19. }
  20. // handleRowValues(rsw, resultMap, defaultResultHandler, rowBounds, null);
  21. public void handleRowValues(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
  22. if (resultMap.hasNestedResultMaps()) {
  23. // 嵌套数据的映射
  24. ensureNoRowBounds();
  25. checkResultHandler();
  26. handleRowValuesForNestedResultMap(rsw, resultMap, resultHandler, rowBounds, parentMapping);
  27. } else {
  28. // 简单数据映射
  29. handleRowValuesForSimpleResultMap(rsw, resultMap, resultHandler, rowBounds, parentMapping);
  30. }
  31. }
  32. // 简单数据映射
  33. private void handleRowValuesForSimpleResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping)
  34. throws SQLException {
  35. DefaultResultContext<Object> resultContext = new DefaultResultContext<>();
  36. ResultSet resultSet = rsw.getResultSet();
  37. // 跳过行偏移,难道不是在数据sql中添加 limit 进行数据筛选的?
  38. skipRows(resultSet, rowBounds);
  39. while (shouldProcessMoreRows(resultContext, rowBounds) && !resultSet.isClosed() && resultSet.next()) {
  40. // 1. Discriminated 鉴别器
  41. ResultMap discriminatedResultMap = resolveDiscriminatedResultMap(resultSet, resultMap, null);
  42. //
  43. Object rowValue = getRowValue(rsw, discriminatedResultMap, null);
  44. storeObject(resultHandler, resultContext, rowValue, parentMapping, resultSet);
  45. }
  46. }
  47. // 检测超过 limit 后,不再继续获取结果
  48. private boolean shouldProcessMoreRows(ResultContext<?> context, RowBounds rowBounds) {
  49. return !context.isStopped() && context.getResultCount() < rowBounds.getLimit();
  50. }
  51. // Discriminated
  52. public ResultMap resolveDiscriminatedResultMap(ResultSet rs, ResultMap resultMap, String columnPrefix) throws SQLException {
  53. Set<String> pastDiscriminators = new HashSet<>();
  54. Discriminator discriminator = resultMap.getDiscriminator();
  55. while (discriminator != null) {
  56. final Object value = getDiscriminatorValue(rs, discriminator, columnPrefix);
  57. final String discriminatedMapId = discriminator.getMapIdFor(String.valueOf(value));
  58. if (configuration.hasResultMap(discriminatedMapId)) {
  59. resultMap = configuration.getResultMap(discriminatedMapId);
  60. Discriminator lastDiscriminator = discriminator;
  61. discriminator = resultMap.getDiscriminator();
  62. if (discriminator == lastDiscriminator || !pastDiscriminators.add(discriminatedMapId)) {
  63. break;
  64. }
  65. } else {
  66. break;
  67. }
  68. }
  69. return resultMap;
  70. }
  71.  
  72. // 从结果set中获取值
  73. private Object getRowValue(ResultSetWrapper rsw, ResultMap resultMap, String columnPrefix) throws SQLException {
  74. final ResultLoaderMap lazyLoader = new ResultLoaderMap();
  75. Object rowValue = createResultObject(rsw, resultMap, lazyLoader, columnPrefix);
  76. if (rowValue != null && !hasTypeHandlerForResultObject(rsw, resultMap.getType())) {
  77. final MetaObject metaObject = configuration.newMetaObject(rowValue);
  78. boolean foundValues = this.useConstructorMappings;
  79. if (shouldApplyAutomaticMappings(resultMap, false)) {
  80. foundValues = applyAutomaticMappings(rsw, resultMap, metaObject, columnPrefix) || foundValues;
  81. }
  82. foundValues = applyPropertyMappings(rsw, resultMap, metaObject, lazyLoader, columnPrefix) || foundValues;
  83. foundValues = lazyLoader.size() > 0 || foundValues;
  84. rowValue = foundValues || configuration.isReturnInstanceForEmptyRow() ? rowValue : null;
  85. }
  86. return rowValue;
  87. }
  88.  
  89. // DefaultResultSetHandler
  90. private Object createResultObject(ResultSetWrapper rsw, ResultMap resultMap, List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix)
  91. throws SQLException {
  92. final Class<?> resultType = resultMap.getType();
  93. final MetaClass metaType = MetaClass.forClass(resultType, reflectorFactory);
  94. final List<ResultMapping> constructorMappings = resultMap.getConstructorResultMappings();
  95. if (hasTypeHandlerForResultObject(rsw, resultType)) {
  96. return createPrimitiveResultObject(rsw, resultMap, columnPrefix);
  97. } else if (!constructorMappings.isEmpty()) {
  98. return createParameterizedResultObject(rsw, resultType, constructorMappings, constructorArgTypes, constructorArgs, columnPrefix);
  99. } else if (resultType.isInterface() || metaType.hasDefaultConstructor()) {
  100. return objectFactory.create(resultType);
  101. } else if (shouldApplyAutomaticMappings(resultMap, false)) {
  102. return createByConstructorSignature(rsw, resultType, constructorArgTypes, constructorArgs, columnPrefix);
  103. }
  104. throw new ExecutorException("Do not know how to create an instance of " + resultType);
  105. }
  106.  
  107. // 构造器注入方式
  108. private Object createByConstructorSignature(ResultSetWrapper rsw, Class<?> resultType, List<Class<?>> constructorArgTypes, List<Object> constructorArgs,
  109. String columnPrefix) throws SQLException {
  110. final Constructor<?>[] constructors = resultType.getDeclaredConstructors();
  111. final Constructor<?> defaultConstructor = findDefaultConstructor(constructors);
  112. if (defaultConstructor != null) {
  113. return createUsingConstructor(rsw, resultType, constructorArgTypes, constructorArgs, columnPrefix, defaultConstructor);
  114. } else {
  115. for (Constructor<?> constructor : constructors) {
  116. if (allowedConstructorUsingTypeHandlers(constructor, rsw.getJdbcTypes())) {
  117. return createUsingConstructor(rsw, resultType, constructorArgTypes, constructorArgs, columnPrefix, constructor);
  118. }
  119. }
  120. }
  121. throw new ExecutorException("No constructor found in " + resultType.getName() + " matching " + rsw.getClassNames());
  122. }
  123.  
  124. private Object createUsingConstructor(ResultSetWrapper rsw, Class<?> resultType, List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix, Constructor<?> constructor) throws SQLException {
  125. boolean foundValues = false;
  126. for (int i = 0; i < constructor.getParameterTypes().length; i++) {
  127. Class<?> parameterType = constructor.getParameterTypes()[i];
  128. String columnName = rsw.getColumnNames().get(i);
  129. TypeHandler<?> typeHandler = rsw.getTypeHandler(parameterType, columnName);
  130. Object value = typeHandler.getResult(rsw.getResultSet(), prependPrefix(columnName, columnPrefix));
  131. constructorArgTypes.add(parameterType);
  132. constructorArgs.add(value);
  133. foundValues = value != null || foundValues;
  134. }
  135. // 调用构造方法注入值
  136. return foundValues ? objectFactory.create(resultType, constructorArgTypes, constructorArgs) : null;
  137. }
  1. // org.apache.ibatis.reflection.factory.DefaultObjectFactory.create(), 调用构造器返回 bean 实例
  2. @SuppressWarnings("unchecked")
  3. @Override
  4. public <T> T create(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
  5. Class<?> classToCreate = resolveInterface(type);
  6. // we know types are assignable
  7. return (T) instantiateClass(classToCreate, constructorArgTypes, constructorArgs);
  8. }
  9.  
  10. private <T> T instantiateClass(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
  11. try {
  12. Constructor<T> constructor;
  13. if (constructorArgTypes == null || constructorArgs == null) {
  14. constructor = type.getDeclaredConstructor();
  15. try {
  16. return constructor.newInstance();
  17. } catch (IllegalAccessException e) {
  18. if (Reflector.canControlMemberAccessible()) {
  19. constructor.setAccessible(true);
  20. return constructor.newInstance();
  21. } else {
  22. throw e;
  23. }
  24. }
  25. }
  26. constructor = type.getDeclaredConstructor(constructorArgTypes.toArray(new Class[constructorArgTypes.size()]));
  27. try {
  28. return constructor.newInstance(constructorArgs.toArray(new Object[constructorArgs.size()]));
  29. } catch (IllegalAccessException e) {
  30. if (Reflector.canControlMemberAccessible()) {
  31. constructor.setAccessible(true);
  32. return constructor.newInstance(constructorArgs.toArray(new Object[constructorArgs.size()]));
  33. } else {
  34. throw e;
  35. }
  36. }
  37. } catch (Exception e) {
  38. StringBuilder argTypes = new StringBuilder();
  39. if (constructorArgTypes != null && !constructorArgTypes.isEmpty()) {
  40. for (Class<?> argType : constructorArgTypes) {
  41. argTypes.append(argType.getSimpleName());
  42. argTypes.append(",");
  43. }
  44. argTypes.deleteCharAt(argTypes.length() - 1); // remove trailing ,
  45. }
  46. StringBuilder argValues = new StringBuilder();
  47. if (constructorArgs != null && !constructorArgs.isEmpty()) {
  48. for (Object argValue : constructorArgs) {
  49. argValues.append(String.valueOf(argValue));
  50. argValues.append(",");
  51. }
  52. argValues.deleteCharAt(argValues.length() - 1); // remove trailing ,
  53. }
  54. throw new ReflectionException("Error instantiating " + type + " with invalid types (" + argTypes + ") or values (" + argValues + "). Cause: " + e, e);
  55. }
  56. }

数据集获取

  1. // 保存结果
  2. private void storeObject(ResultHandler<?> resultHandler, DefaultResultContext<Object> resultContext, Object rowValue, ResultMapping parentMapping, ResultSet rs) throws SQLException {
  3. if (parentMapping != null) {
  4. linkToParents(rs, parentMapping, rowValue);
  5. } else {
  6. callResultHandler(resultHandler, resultContext, rowValue);
  7. }
  8. }
  9.  
  10. @SuppressWarnings("unchecked" /* because ResultHandler<?> is always ResultHandler<Object>*/)
  11. private void callResultHandler(ResultHandler<?> resultHandler, DefaultResultContext<Object> resultContext, Object rowValue) {
  12. resultContext.nextResultObject(rowValue);
  13. ((ResultHandler<Object>) resultHandler).handleResult(resultContext);
  14. }
  15. //
  16. private boolean applyPropertyMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, ResultLoaderMap lazyLoader, String columnPrefix)
  17. throws SQLException {
  18. final List<String> mappedColumnNames = rsw.getMappedColumnNames(resultMap, columnPrefix);
  19. boolean foundValues = false;
  20. final List<ResultMapping> propertyMappings = resultMap.getPropertyResultMappings();
  21. for (ResultMapping propertyMapping : propertyMappings) {
  22. String column = prependPrefix(propertyMapping.getColumn(), columnPrefix);
  23. if (propertyMapping.getNestedResultMapId() != null) {
  24. // the user added a column attribute to a nested result map, ignore it
  25. column = null;
  26. }
  27. if (propertyMapping.isCompositeResult()
  28. || (column != null && mappedColumnNames.contains(column.toUpperCase(Locale.ENGLISH)))
  29. || propertyMapping.getResultSet() != null) {
  30. Object value = getPropertyMappingValue(rsw.getResultSet(), metaObject, propertyMapping, lazyLoader, columnPrefix);
  31. // issue #541 make property optional
  32. final String property = propertyMapping.getProperty();
  33. if (property == null) {
  34. continue;
  35. } else if (value == DEFERED) {
  36. foundValues = true;
  37. continue;
  38. }
  39. if (value != null) {
  40. foundValues = true;
  41. }
  42. if (value != null || (configuration.isCallSettersOnNulls() && !metaObject.getSetterType(property).isPrimitive())) {
  43. // gcode issue #377, call setter on nulls (value is not 'found')
  44. metaObject.setValue(property, value);
  45. }
  46. }
  47. }
  48. return foundValues;
  49. }
  50.  
  51. // collapseSingleResultList(multipleResults); 转换多级 list 为1级list
  52. @SuppressWarnings("unchecked")
  53. private List<Object> collapseSingleResultList(List<Object> multipleResults) {
  54. return multipleResults.size() == 1 ? (List<Object>) multipleResults.get(0) : multipleResults;
  55. }

至此,一条select 语句搞定!

主要经历几个阶段:
  1. 加载配置
  2. 创建sqlSessionFactory
  3. 获取sqlSession
  4. jdbc连接
  5. 获取mapper
  6. 查询参数绑定
  7. 获取db结果
  8. 处理返回集字段映射
  9. 缓存结果
  10. 返回结果

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