/**
* 增强Mapper处理总入口:Mapper被mybatis初始化后,在这里做进一步的处理和增强
*
* @author qigong on 5/1/15
*/
public class MapperShardingInitializer implements ApplicationContextAware { Logger logger = LoggerFactory.getLogger(getClass()); private String needEnhancedClasses;
private String[] needEnhancedClassesArray; @Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
Map<String, SqlSessionFactory> sqlSessionFactories = applicationContext.getBeansOfType(SqlSessionFactory.class);
if (sqlSessionFactories.isEmpty()) {
return;
}
MapperHelperForSharding mapperHelperForSharding = new MapperHelperForSharding();
List<SqlSession> sqlSessions = new ArrayList<>(sqlSessionFactories.size());
for (SqlSessionFactory sqlSessionFactory : sqlSessionFactories.values()) {
SqlSession sqlSession = new SqlSessionTemplate(sqlSessionFactory);
sqlSessions.add(sqlSession);
}
//Mapper代码增强 每个方法扩展出一个ShardingMapper类,增强为512个方法。
this.needEnhancedClassesArray = needEnhancedClasses.split(",");
this.enhanceMapperClass();
mapperHelperForSharding.setMappers(needEnhancedClassesArray);
mapperHelperForSharding.setSqlSessions(sqlSessions.toArray(new SqlSession[0]));
mapperHelperForSharding.initMapper();
} private void enhanceMapperClass() {
for (String mapperClass : needEnhancedClassesArray) {
try {
MapperEnhancer.enhanceMapperClass(mapperClass);
} catch (Exception e) {
logger.error("Enhance {} class error", mapperClass, e);
}
}
} public void setNeedEnhancedClasses(String needEnhancedClasses) {
this.needEnhancedClasses = needEnhancedClasses;
}
}

 

3.1 this.enhanceMapperClass();

  

 /**
* 对mapper进行增强,生成新的mapper,并主动加载新mapper类到classloader
*
* @param mapperClassName
*/
public static void enhanceMapperClass(String mapperClassName) throws Exception {
//com.mogujie.service.tsharding.mapper.ShopOrderMapper
Class originClass = Class.forName(mapperClassName);//获取A
Method[] originMethods = originClass.getDeclaredMethods();//获取A的方法, CtClass cc = pool.get(mapperClassName);//获取到class定义的容器ClassPool,通过它获取已经编译好的类A for (CtMethod ctMethod : cc.getDeclaredMethods()) {//遍历A的所有方法
CtClass enhanceClass = pool.makeInterface(mapperClassName + "Sharding" + ctMethod.getName());//针对A的每一个方法新建一个接口B
//com.mogujie.service.tsharding.mapper.ShopOrderMapperShardinggetShopOrderByShopOrderId
for (long i = 0L; i < 512; i++) {//生成512个方法
CtMethod newMethod = new CtMethod(ctMethod.getReturnType(), ctMethod.getName() + ShardingCaculator.getNumberWithZeroSuffix(i), ctMethod.getParameterTypes(), enhanceClass);
//CtMethod 和CtConstructor 提供了 insertBefore()、insertAfter()和 addCatch()方法,它们可以插入一个souce文本到存在的方法的相应的位置
Method method = getOriginMethod(newMethod, originMethods);//获取A的方法
if(method.getParameterAnnotations()[0].length > 0) {//如果带注解
ClassFile ccFile = enhanceClass.getClassFile();
ConstPool constPool = ccFile.getConstPool(); //拷贝注解信息和注解内容,以支持mybatis mapper类的动态绑定
newMethod.getMethodInfo().addAttribute(MapperAnnotationEnhancer.duplicateParameterAnnotationsAttribute(constPool, method));
}
enhanceClass.addMethod(newMethod);//B增加方法
}
Class<?> loadThisClass = enhanceClass.toClass(); //2015.09.22后不再输出类到本地
enhanceClass.writeFile(".");
}
}

  需要增强的类

@DataSourceRouting(handler=TShardingRoutingHandler.class)
public abstract interface ShopOrderMapper
{
@ShardingExtensionMethod(type=MapperResourceEnhancer.class, method="enhancedShardingSQL")
public abstract ShopOrder getShopOrderByShopOrderId(@ShardingOrderPara Long paramLong); @ShardingExtensionMethod(type=MapperResourceEnhancer.class, method="enhancedShardingSQL")
public abstract List<ShopOrder> getShopOrderByShopOrderIds(@ShardingOrderPara List<Long> paramList); @ShardingExtensionMethod(type=MapperResourceEnhancer.class, method="enhancedShardingSQL")
public abstract int batchUpdateShopOrderByShopOrderIds(@ShardingOrderPara @Param("shopOrderIds") List<Long> paramList, @Param("shopOrder") ShopOrder paramShopOrder);
}

增强后针对每一个方法都生成了一个类

public abstract interface ShopOrderMapperShardingbatchUpdateShopOrderByShopOrderIds
{
public abstract int batchUpdateShopOrderByShopOrderIds0000(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder); public abstract int batchUpdateShopOrderByShopOrderIds0001(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder); public abstract int batchUpdateShopOrderByShopOrderIds0002(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder); public abstract int batchUpdateShopOrderByShopOrderIds0003(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder); public abstract int batchUpdateShopOrderByShopOrderIds0004(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder);
public abstract interface ShopOrderMapperShardinggetShopOrderByShopOrderId
{
public abstract ShopOrder getShopOrderByShopOrderId0000(@ShardingOrderPara("orderId") Long paramLong); public abstract ShopOrder getShopOrderByShopOrderId0001(@ShardingOrderPara("orderId") Long paramLong); public abstract ShopOrder getShopOrderByShopOrderId0002(@ShardingOrderPara("orderId") Long paramLong); public abstract ShopOrder getShopOrderByShopOrderId0003(@ShardingOrderPara("orderId") Long paramLong); public abstract ShopOrder getShopOrderByShopOrderId0004(@ShardingOrderPara("orderId") Long paramLong); public abstract ShopOrder getShopOrderByShopOrderId0005(@ShardingOrderPara("orderId") Long paramLong); public abstract ShopOrder getShopOrderByShopOrderId0006(@ShardingOrderPara("orderId") Long paramLong); public abstract ShopOrder getShopOrderByShopOrderId0007(@ShardingOrderPara("orderId") Long paramLong);
}
public abstract interface ShopOrderMapperShardinggetShopOrderByShopOrderIds
{
public abstract List getShopOrderByShopOrderIds0000(@ShardingOrderPara("orderId") List paramList); public abstract List getShopOrderByShopOrderIds0001(@ShardingOrderPara("orderId") List paramList); public abstract List getShopOrderByShopOrderIds0002(@ShardingOrderPara("orderId") List paramList); public abstract List getShopOrderByShopOrderIds0003(@ShardingOrderPara("orderId") List paramList); public abstract List getShopOrderByShopOrderIds0004(@ShardingOrderPara("orderId") List paramList); public abstract List getShopOrderByShopOrderIds0005(@ShardingOrderPara("orderId") List paramList); public abstract List getShopOrderByShopOrderIds0006(@ShardingOrderPara("orderId") List paramList); public abstract List getShopOrderByShopOrderIds0007(@ShardingOrderPara("orderId") List paramList);
}

3.2 mapperHelperForSharding.setMappers(needEnhancedClassesArray);
  通过ShopOrderMapper.java,获取注解配置 @ShardingExtensionMethod(type = MapperResourceEnhancer.class, method = "enhancedShardingSQL"),
  生成MapperEnhancer,以ShopOrderMapper的方法名为key,MapperResourceEnhancer.enhancedShardingSQL 为value,保存在MapperResourceEnhancer.methodMap中。
  返回MapperEnhancer,再以ShopOrderMappe 为key,MapperEnhancer为value,保存在MapperHelperForSharding.registerMapper中,供后续使用
3.3 mapperHelperForSharding.setSqlSessions(sqlSessions.toArray(new SqlSession[0]));
  把sqlSession保存在mapperHelperForSharding.sqlSessions
3.4 mapperHelperForSharding.initMapper();( Spring4 is necessary)
  类关系:SqlSession>Configuration>MappedStatement>DynamicSqlSource||RawSqlSource
  遍历 sqlSessions,处理Configuration中全部的MappedStatement,重新设置SqlSource。
  重新设置SqlSource:获取MapperTemplate(3.2mapperHelperForSharding.registerMapper中保存的MapperEnhancer)。
  然后 mapperEnhancer.setSqlSource(ms, configuration);代码增强 扩充为512个方法。

  

public void setSqlSource(MappedStatement ms, Configuration configuration) throws Exception {
Method method = methodMap.get(getMethodName(ms));//3.2中保存的enhancedShardingSQL方法
try {
if (method.getReturnType() == Void.TYPE) {
method.invoke(this, ms);
} else if (SqlSource.class.isAssignableFrom(method.getReturnType())) {
//代码增强 扩充为512个方法。
for (long i = 0; i < 512; i++) { //新的带sharding的sql
SqlSource sqlSource = (SqlSource) method.invoke(this, ms, configuration, i); String newMsId = ms.getId() + ShardingCaculator.getNumberWithZeroSuffix(i);
newMsId = newMsId.replace("Mapper.", "MapperSharding" + getMethodName(ms) + "."); //添加到ms库中
MappedStatement newMs = copyFromMappedStatement(ms, sqlSource, newMsId);
configuration.addMappedStatement(newMs);
setSqlSource(newMs, sqlSource);
}
} else {
throw new RuntimeException("自定义Mapper方法返回类型错误,可选的返回类型为void和SqlNode!");
}
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
} catch (InvocationTargetException e) {
throw new RuntimeException(e.getTargetException() != null ? e.getTargetException() : e);
}
}

3.4.1 SqlSource sqlSource = (SqlSource) method.invoke(this, ms, configuration, i);
  实际调用com.mogujie.trade.tsharding.route.orm.MapperResourceEnhancer;enhancedShardingSQL
    (SqlSession>Configuration>MappedStatement>DynamicSqlSource||RawSqlSource)
     DynamicSqlSource中存在mapperxml中每个节点的语句。
       awSqlSource中存在mapperxml中的sql语句。根据分片参数替换成对应的表名,比如TradeOrder0066
    最终生成的sql语句类似(SELECT orderId, buyerUserId,sellerUserId FROM TradeOrder0066 WHERE orderId = ? limit 1)
  用新ID,创建MappedStatement(mapperxml节点),添加到Configuration,设置数据源
     新ID格式:com.mogujie.service.tsharding.mapper.ShopOrderMapperShardinggetShopOrderByShopOrderId.getShopOrderByShopOrderId0000

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