多数据源一般解决哪些问题？主从模式或者业务比较复杂需要连接不同的分库来支持业务。

直接上代码。

配置文件

pom包依赖，该依赖的依赖。主要是数据库这边的配置：

mybatis.config-locations=classpath:mybatis/mybatis-config.xmlspring.datasource.test1.driverClassName = com.mysql.jdbc.Driver
spring.datasource.test1.url = jdbc:mysql://localhost:3306/test1?useUnicode=true&characterEncoding=utf-8
spring.datasource.test1.username = root
spring.datasource.test1.password = rootspring.datasource.test2.driverClassName = com.mysql.jdbc.Driver
spring.datasource.test2.url = jdbc:mysql://localhost:3306/test2?useUnicode=true&characterEncoding=utf-8
spring.datasource.test2.username = root
spring.datasource.test2.password = root

一个test1和一个test2库，其中test1为主库，必须指定主库，不然会报错。

数据源配置

@Configuration
@MapperScan(basePackages = "com.neo.mapper.test1", sqlSessionTemplateRef  = "test1SqlSessionTemplate")
public class DataSource1Config {@Bean(name = "test1DataSource")@ConfigurationProperties(prefix = "spring.datasource.test1")@Primarypublic DataSource testDataSource() {return DataSourceBuilder.create().build();}@Bean(name = "test1SqlSessionFactory")@Primarypublic SqlSessionFactory testSqlSessionFactory(@Qualifier("test1DataSource") DataSource dataSource) throws Exception {SqlSessionFactoryBean bean = new SqlSessionFactoryBean();bean.setDataSource(dataSource);bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/test1/*.xml"));return bean.getObject();}@Bean(name = "test1TransactionManager")@Primarypublic DataSourceTransactionManager testTransactionManager(@Qualifier("test1DataSource") DataSource dataSource) {return new DataSourceTransactionManager(dataSource);}@Bean(name = "test1SqlSessionTemplate")@Primarypublic SqlSessionTemplate testSqlSessionTemplate(@Qualifier("test1SqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {return new SqlSessionTemplate(sqlSessionFactory);}}

最关键的地方就是这一块了，一层一层注入，首先创建DataSource，然后创建SqlSessionFactory再创建事务，最后包装到SQLSessionTemplate中。其中需要指定分库的mapper文件地址。

@MapperScan(basePackages = "com.neo.mapper.test1", sqlSessionTemplateRef  = "test1SqlSessionTemplate")

这块的注解就是指明了扫描的dao层，并且给dao层注入指定的SQLSessionTemplate，所有@Bean 都需要按照命名指定正确。

dao层和xml层

dao层和xml需要按照库来区分在不同的目录，比如：test1库dao层在com.neo.mapper.test1包下，test2库在com.neo.mapper.test2下

public interface User1Mapper {List<UserEntity> getAll();UserEntity getOne(Long id);void insert(UserEntity user);void update(UserEntity user);void delete(Long id);}

xml层

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.neo.mapper.test1.User1Mapper" >			<!--命名空间--><resultMap id="BaseResultMap" type="com.neo.entity.UserEntity" >		<!--结果集-->		<id column="id" property="id" jdbcType="BIGINT" /><result column="userName" property="userName" jdbcType="VARCHAR" /><result column="passWord" property="passWord" jdbcType="VARCHAR" /><result column="user_sex" property="userSex" javaType="com.neo.enums.UserSexEnum"/><result column="nick_name" property="nickName" jdbcType="VARCHAR" /></resultMap><sql id="Base_Column_List" >id, userName, passWord, user_sex, nick_name</sql><select id="getAll" resultMap="BaseResultMap"  >SELECT <include refid="Base_Column_List" />FROM users</select><select id="getOne" parameterType="java.lang.Long" resultMap="BaseResultMap" >SELECT <include refid="Base_Column_List" />FROM usersWHERE id = #{id}</select><insert id="insert" parameterType="com.neo.entity.UserEntity" >INSERT INTO users(userName,passWord,user_sex) VALUES(#{userName}, #{passWord}, #{userSex})</insert><update id="update" parameterType="com.neo.entity.UserEntity" >UPDATE users SET <if test="userName != null">userName = #{userName},</if><if test="passWord != null">passWord = #{passWord},</if>nick_name = #{nickName}WHERE id = #{id}</update><delete id="delete" parameterType="java.lang.Long" >DELETE FROMusers WHERE id =#{id}</delete></mapper>

测试

测试可以使用SpringBootTest，也可以放到Controller中，这里只贴Controller层的使用。

@RestController
public class UserController {@Autowiredprivate User1Mapper user1Mapper;@Autowiredprivate User2Mapper user2Mapper;@RequestMapping("/getUsers")public List<UserEntity> getUsers() {List<UserEntity> users=user1Mapper.getAll();return users;}@RequestMapping("/getUser")public UserEntity getUser(Long id) {UserEntity user=user2Mapper.getOne(id);return user;}@RequestMapping("/add")public void save(UserEntity user) {user2Mapper.insert(user);}@RequestMapping(value="update")public void update(UserEntity user) {user2Mapper.update(user);}@RequestMapping(value="/delete/{id}")public void delete(@PathVariable("id") Long id) {user1Mapper.delete(id);}
}

项目地址(码云)