spring boot(四) 多数据源

前言

前一篇中我们使用spring boot+mybatis创建了单一数据源，其中单一数据源不需要我们自己手动创建，spring boot自动配置在程序启动时会替我们创建好数据源。

准备工作

application.yml中配置connection的4个属性

spring:
  datasource:
    read:
      driver-class-name: com.mysql.jdbc.Driver
      url: jdbc:mysql://192.168.80.129:3306/test
      username: root
      password: 123456
    write:
      driver-class-name: com.mysql.jdbc.Driver
      url: jdbc:mysql://192.168.80.129:3306/test
      username: root
      password: 123456

　　

多数据源创建方法

1、多数据源主要是需要我们手动来创建DataSource、SqlSessionFactory、SqlSessionTemplate。这里我们基于同一个库来创建读写分离的数据源。这里两个方法的返回值都是javax.sql.DataSource。

@Configuration
public class DataSourceConfig {

    @Primary
    @Bean(name="readDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.read")
    public DataSource readDataSource(){
        return DataSourceBuilder.create().build();
    }

    @Bean(name="writeDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.write")
    public DataSource writeDataSource(){
        return DataSourceBuilder.create().build();
    }

}

　2、读写分离的配置类。也就是分别创建读写的SqlSessionFactory和SqlSessionTemplate

@Configuration
@MapperScan(basePackages = {"com.zhangfei.dao.read"},sqlSessionFactoryRef = "readSqlSessionFactory")
public class MyBatisDbAConfig {

    @Autowired
    @Qualifier("readDataSource")
    private DataSource dataSource;

    @Bean
    public SqlSessionFactory readSqlSessionFactory() throws Exception{
        SqlSessionFactoryBean sqlSessionFactoryBean=new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSource);

        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        Resource[] resource=resolver.getResources("classpath:mybatis/read/*.xml");
        sqlSessionFactoryBean.setMapperLocations(resource);

        return sqlSessionFactoryBean.getObject();
    }

    @Bean
    public SqlSessionTemplate readSqlSession() throws Exception{
        SqlSessionTemplate sqlSessionTemplate=new SqlSessionTemplate(readSqlSessionFactory());

        return sqlSessionTemplate;
    }
}

　　

@Configuration
@MapperScan(basePackages = {"com.zhangfei.dao.write"},sqlSessionFactoryRef = "writeSqlSessionFactory")
public class MyBatisDbBConfig {

    @Autowired
    @Qualifier("writeDataSource")
    private DataSource dataSource;

    @Bean
    public SqlSessionFactory writeSqlSessionFactory() throws Exception{
        SqlSessionFactoryBean sqlSessionFactoryBean=new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSource);

        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        Resource[] resource=resolver.getResources("classpath:mybatis/write/*.xml");
        sqlSessionFactoryBean.setMapperLocations(resource);

        return sqlSessionFactoryBean.getObject();
    }

    @Bean
    public SqlSessionTemplate writeSqlSession() throws Exception{
        SqlSessionTemplate sqlSessionTemplate=new SqlSessionTemplate(writeSqlSessionFactory());

        return sqlSessionTemplate;
    }

}

　　3、read包下的dao接口

public interface StudentReadDao {

    List<Student> getStudentList();

    Student getById(long id);

}

　4、wite包下的dao接口

public interface StudentWriteDao {

    int delete(long id);

    int insert(Student student);

    int update(Student student);

}

　5、分别创建读写的mapper文件。我本地分别创建了：resources/mybatis/read/studentdao.xml、/resources/mybatis/write/studentdao.xml

<?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.zhangfei.dao.read.StudentReadDao">
    <select id="getStudentList" resultType="com.zhangfei.entity.Student">
        select * from student;
    </select>

    <select id="getById" resultType="com.zhangfei.entity.Student">
        select * from student where id=#{id};
    </select>

</mapper>

　　

<?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.zhangfei.dao.write.StudentWriteDao">

    <insert id="insert" parameterType="com.zhangfei.entity.Student">
        insert into student (name,age) values (#{name},#{age})
    </insert>

    <update id="update" parameterType="com.zhangfei.entity.Student">
        update student set name=#{name},age=#{age} where id=#{id}
    </update>

    <delete id="delete" parameterType="long">
        delete from student where id=#{id}
    </delete>
</mapper>

　　OK。以上几部就搞定了读写分离的准备工作，接着就可以在controller里调用了。 准备工作完成后，还有重要的一点就是需要在程序入口处排除springboot自动属性提供的数据源  @SpringBootApplication(exclude = DataSourceAutoConfiguration.class)

@RestController
@RequestMapping("/student")
public class StudentController {

    @Autowired
    StudentReadDao studentDao;

    @GetMapping("/getbyid/{id}/")
    public Student getById(@PathVariable("id")long id){

        Student student=studentDao.getById(id);
        return student;
    }

    @GetMapping("/all/")
    public List<Student> getAll(){
        return studentDao.getStudentList();
    }

}

　　

总结

好了，基本上又是3分钟就搞定了SpringBoot+MyBatis多数据源或者叫做读写分离的工作。那么不知道你又没有反问我们手动创建的DataSource具体类型是什么呢？ 这里我们在这里只写了javax.sql.DataSource接口。 我本地用的是springboot 2.0.2 ，当前 DataSourceBuilder 只支持3种类型的数据源： com.zaxxer.hikari.HikariDataSource、org.apache.tomcat.jdbc.pool.DataSource、org.apache.commons.dbcp2.BasicDataSource。可以在DataSourceBuilder类中看到相关代码。那么现在这种情况因为我们引用的内嵌tomcat，所以我们这里返回的数据源类型是org.apache.tomcat.jdbc.pool.DataSource。 可以用instanceof验证一下具体的数据源类型。