spring-boot支持双数据源mysql+mongo

这里，首先想说的是，现在的web应用，处理的数据对象，有结构化的，也有非结构化的。同时存在。但是在spring-boot操作数据库的时候，若是在properties文件中配置数据源的信息，通过默认配置加载数据源的话，往往只会启动一个。

我出于想弄清如何配置数据源的目的，在这里demo一个配置两个数据源的例子。分别是mysql和mongo。mysql的持久化采用的是mybatis。

mongo的操作比较简单，直接贴上配置数据库的代码：

 package com.shihuc.dbconn.sourceconfig.mongo;
 
 import java.util.Arrays;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration;
 import org.springframework.boot.autoconfigure.mongo.MongoDataAutoConfiguration;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.data.mongodb.config.AbstractMongoConfiguration;
 import org.springframework.data.mongodb.repository.config.EnableMongoRepositories;
 
 import com.mongodb.Mongo;
 import com.mongodb.MongoClient;
 import com.mongodb.MongoCredential;
 import com.mongodb.ServerAddress;
 import com.mongodb.WriteConcern;
 
 @Configuration
 @EnableAutoConfiguration(exclude={MongoAutoConfiguration.class, MongoDataAutoConfiguration.class})
 @ComponentScan
 @EnableMongoRepositories
 public class MongoDataSourceConfig extends AbstractMongoConfiguration{
 
     @Value("${mongo.database}")
     private String dbname;
 
     @Value("${mongo.host}")
     private String dbhost;
 
     @Value("${mongo.port}")
     private String dbport;
 
     @Value("${mongo.username}")
     private String username;
 
     @Value("${mongo.password}")
     private String password;
 
     @Override
     protected String getDatabaseName() {
         return this.dbname;
     }
 
     public MongoDataSourceConfig(){
         if(null == dbport || "".equalsIgnoreCase(dbport.trim())){
             dbport = "27017";
         }
     }
 
     @Override
     @Bean(name = "mongods")
     public Mongo mongo() throws Exception {
         ServerAddress serverAdress = new  ServerAddress(dbhost, Integer.valueOf(dbport));
         MongoCredential credential = MongoCredential.createMongoCRCredential(username, dbname , password.toCharArray());
         //Do not use new Mongo(), is deprecated.
         Mongo mongo =  new MongoClient(serverAdress, Arrays.asList(credential));
         mongo.setWriteConcern(WriteConcern.SAFE);
         return mongo;
     }
 }

mongo数据库配置继承AbstractMongoConfiguration，在这个过程中，会向spring容器注册一个mongoTemplate，这个很重要，后期操作mongo数据库时，主要靠它。

这里重点说下spring-boot和mybatis集成操作mysql的配置和注意事项。

 package com.shihuc.dbconn.sourceconfig.mysql;
 
 import javax.sql.DataSource;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.jdbc.datasource.DriverManagerDataSource;
 
 @Configuration
 @EnableAutoConfiguration(exclude = {DataSourceAutoConfiguration.class})
 public class MysqlDataSourceConfig {
 
     @Value("${mysql.driver}")
     private String driver;
 
     @Value("${mysql.url}")
     private String url;
 
     @Value("${mysql.username}")
     private String username;
 
     @Value("${mysql.password}")
     private String password;
 
     @Bean(name="mysqlds")
     public DataSource mysql()
     {
         DriverManagerDataSource ds = new DriverManagerDataSource();
         ds.setDriverClassName(driver);
         ds.setUrl(url);
         ds.setUsername(username);
         ds.setPassword(password);
         return ds;
     }
 }

这个是datasource的配置，注意，类似mongo的配置，要将自动配置的类给exclude掉。让spring只处理我们希望的数据源。否则会受到classpath下的信息，干扰数据源的配置。

另外，就是mybatis的配置。由于spring-boot重点特色是纯java config，所以，这里也采用java配置和注解启用mybatis。

 package com.shihuc.dbconn.sourceconfig.mysql;
 
 import javax.sql.DataSource;
 
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.mybatis.spring.SqlSessionFactoryBean;
 import org.mybatis.spring.annotation.MapperScan;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
 @Configuration
 @MapperScan(basePackages = "com.shihuc.dbconn.dao.mysql")
 public class MysqlMybatisConfig {
 
     @Autowired
     @Qualifier("mysqlds")
     private DataSource mysqlds;
 
     @Bean
     public SqlSessionFactory sqlSessionFactoryBean() throws Exception {
         final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
         sessionFactory.setDataSource(mysqlds);
         return sessionFactory.getObject();
     }
 }

这里，mapperscan主要是为配置JavaBean和持久化对象之间的映射关系设定根路径。在这个例子中，mapper部分，其实就是通过insert,delete,update,select等注解，结合具体的SQL语句实现ORM的关系。看看这里的代码：

 package com.shihuc.dbconn.dao.mysql;
 
 import org.apache.ibatis.annotations.Insert;
 import org.apache.ibatis.annotations.Select;
 
 import com.shihuc.dbconn.pojo.mysql.MysqlUser;
 
 public interface IMysqlUser {
 
     @Select("SELECT * FROM user WHERE id = #{userId}")
     public MysqlUser getUser(int userId);
 
     @Insert("insert into user (username, job, age, hometown) values(#{username}, #{job}, #{age}, #{hometown})")
     public int addUser(MysqlUser user);
 }

另外，配合这个IMysqlUser使用的MysqlUser的定义也很重要，主要是里面的constructor函数，通常，添加数据，比如上面的addUser操作，是要创建一个POJO的对象，为了方便，一般都会创建一个带参数的构造函数，注意，必须也同时创建一个无参数的构造函数，否则，在做查询操作，比如上面的getUser时，会出现下面的错误：

   .   ____          _            __ _ _
  /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
 ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
  \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
   '  |____| .__|_| |_|_| |_\__, | / / / /
  =========|_|==============|___/=/_/_/_/
  :: Spring Boot ::        (v1.2.7.RELEASE)
 
 2016-01-29 15:01:07.930  INFO 30880 --- [           main] com.shihuc.dbconn.DbConnApp              : Starting DbConnApp on CloudGame with PID 30880 (/home/webWps/dbconn/target/classes started by root in /home/webWps/dbconn)
 2016-01-29 15:01:07.997  INFO 30880 --- [           main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@a85aa40: startup date [Fri Jan 29 15:01:07 CST 2016]; root of context hierarchy
 2016-01-29 15:01:09.887  INFO 30880 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'mysqlDataSourceConfig' of type [class com.shihuc.dbconn.sourceconfig.mysql.MysqlDataSourceConfig$$EnhancerBySpringCGLIB$$63c6820a] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
 2016-01-29 15:01:09.915  INFO 30880 --- [           main] o.s.j.d.DriverManagerDataSource          : Loaded JDBC driver: com.mysql.jdbc.Driver
 2016-01-29 15:01:09.923  INFO 30880 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'mysqlds' of type [class org.springframework.jdbc.datasource.DriverManagerDataSource] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
 2016-01-29 15:01:09.926  INFO 30880 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'mysqlMybatisConfig' of type [class com.shihuc.dbconn.sourceconfig.mysql.MysqlMybatisConfig$$EnhancerBySpringCGLIB$$bbfde9e4] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
 2016-01-29 15:01:09.991  INFO 30880 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'sqlSessionFactoryBean' of type [class org.apache.ibatis.session.defaults.DefaultSqlSessionFactory] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
 2016-01-29 15:01:10.040  INFO 30880 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'IMysqlUser' of type [class org.mybatis.spring.mapper.MapperFactoryBean] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
 2016-01-29 15:01:10.876  INFO 30880 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
 2016-01-29 15:01:10.888  INFO 30880 --- [           main] com.shihuc.dbconn.DbConnApp              : Started DbConnApp in 3.274 seconds (JVM running for 3.561)
 Exception in thread "main" org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.reflection.ReflectionException: Error instantiating class com.shihuc.dbconn.pojo.mysql.MysqlUser with invalid types () or values (). Cause: java.lang.NoSuchMethodException: com.shihuc.dbconn.pojo.mysql.MysqlUser.<init>()
     at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:75)
     at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:371)
     at com.sun.proxy.$Proxy26.selectOne(Unknown Source)
     at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:163)
     at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:63)
     at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:43)
     at com.sun.proxy.$Proxy34.getUser(Unknown Source)
     at com.shihuc.dbconn.service.mysql.MysqlUserService.getUser(MysqlUserService.java:20)
     at com.shihuc.dbconn.DbConnApp.main(DbConnApp.java:34)
 Caused by: org.apache.ibatis.reflection.ReflectionException: Error instantiating class com.shihuc.dbconn.pojo.mysql.MysqlUser with invalid types () or values (). Cause: java.lang.NoSuchMethodException: com.shihuc.dbconn.pojo.mysql.MysqlUser.<init>()
     at org.apache.ibatis.reflection.factory.DefaultObjectFactory.instantiateClass(DefaultObjectFactory.java:83)
     at org.apache.ibatis.reflection.factory.DefaultObjectFactory.create(DefaultObjectFactory.java:45)
     at org.apache.ibatis.reflection.factory.DefaultObjectFactory.create(DefaultObjectFactory.java:38)
     at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createResultObject(DefaultResultSetHandler.java:530)
     at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createResultObject(DefaultResultSetHandler.java:509)
     at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:329)
     at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:289)
     at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:264)
     at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:234)
     at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:152)
     at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:57)
     at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:70)
     at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:57)
     at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:259)
     at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:132)
     at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:105)
     at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:81)
     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:98)
     at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:62)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
     at java.lang.reflect.Method.invoke(Method.java:606)
     at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:358)
     ... 7 more
 Caused by: java.lang.NoSuchMethodException: com.shihuc.dbconn.pojo.mysql.MysqlUser.<init>()
     at java.lang.Class.getConstructor0(Class.java:2892)
     at java.lang.Class.getDeclaredConstructor(Class.java:2058)
     at org.apache.ibatis.reflection.factory.DefaultObjectFactory.instantiateClass(DefaultObjectFactory.java:57)
     ... 31 more
 2016-01-29 15:01:11.139  INFO 30880 --- [       Thread-1] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@a85aa40: startup date [Fri Jan 29 15:01:07 CST 2016]; root of context hierarchy
 2016-01-29 15:01:11.142  INFO 30880 --- [       Thread-1] o.s.j.e.a.AnnotationMBeanExporter        : Unregistering JMX-exposed beans on shutdown

方便说明问题，将MysqlUser也附上代码：

 package com.shihuc.dbconn.pojo.mysql;
 
 import com.shihuc.dbconn.pojo.User;
 
 public class MysqlUser extends User{
 
     private static final long serialVersionUID = -6412107575129572581L;
 
     //这个id是数据库中通过设置auto_increment得到的主键值
     private int id;
 
     public int getId() {
         return id;
     }
 
     public void setId(int id) {
         this.id = id;
     }
 
     public MysqlUser(){
 
     }
 
     public MysqlUser(String username, String job, int age, String hometown){
         this.username = username;
         this.job = job;
         this.age = age;
         this.hometown = hometown;
     }
 
 }

下面看看，测试程序吧，我是在main函数里面写的，如下：

 package com.shihuc.dbconn;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.PropertySource;
 
 import com.shihuc.dbconn.pojo.mongo.MongoUser;
 import com.shihuc.dbconn.pojo.mysql.MysqlUser;
 import com.shihuc.dbconn.service.mongo.MongoUserService;
 import com.shihuc.dbconn.service.mysql.MysqlUserService;
 
 /**
  *
  * @author  shihuc
  * @date    Jan 29, 2016
  *
  */
 @SpringBootApplication
 @PropertySource(value = "dbconn.properties")
 public class DbConnApp
 {
 
        public static void main(String[] args) throws Throwable {
 
         SpringApplication app = new SpringApplication(DbConnApp.class);
 
         ApplicationContext ctx = app.run(args);        
 
         MysqlUserService mysqlUserService = (MysqlUserService)ctx.getBean("mysqlUserService");
 //        MysqlUser su = new MysqlUser("shihuc", "SW", 30 , "wuhan");
 //        mysqlUserService.addUser(su);
         MysqlUser ue = mysqlUserService.getUser(1);
         System.out.println("Mysql User: " + ue);        
 
         MongoUserService mongoUserService = (MongoUserService)ctx.getBean("mongoUserService");
 //        MongoUser mu = new MongoUser("shihuc", "SW", 30 , "wuhan");
 //        mongoUserService.addUser(mu);
         MongoUser um = mongoUserService.getUser("shihuc");
         System.out.println("Mongo User: " + um);
     }
 }

最后附上我的maven项目的pom文件：

 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
 
   <groupId>com.shihuc</groupId>
   <artifactId>dbconn</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>
 
   <name>dbconn</name>
   <url>http://maven.apache.org</url>
 
   <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
         <version>1.2.7.RELEASE</version>
   </parent>
 
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   </properties>
 
   <dependencies>
       <dependency>
           <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-jdbc</artifactId>
     </dependency>
     <dependency>
         <groupId>mysql</groupId>
         <artifactId>mysql-connector-java</artifactId>
         </dependency>
     <dependency>
         <groupId>org.mybatis</groupId>
         <artifactId>mybatis</artifactId>
         <version>3.2.3</version>
     </dependency>
     <dependency>
         <groupId>org.mybatis</groupId>
         <artifactId>mybatis-spring</artifactId>
         <version>1.2.2</version>
     </dependency>
     <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-data-mongodb</artifactId>
     </dependency>
   </dependencies>
 
   <build>
     <plugins>
         <plugin>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
     </plugins>
   </build>
 </project>

还是相对比较简单的配置和操作。对于这个demo的例子程序，可以在GitHub https://github.com/shihuc/dbconn上下载。