spring boot(四) 多數據源

前言

        前一篇中我們使用spring boot+mybatis創建了單一數據源，其中單一數據源不需要我們自己手動創建，spring boot自動配置在程序啟動時會替我們創建好數據源。

准備工作

       application.yml中配置connection的4個屬性

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

　　

多數據源創建方法

      1、多數據源主要是需要我們手動來創建DataSource、SqlSessionFactory、SqlSessionTemplate。這里我們基於同一個庫來創建讀寫分離的數據源。這里兩個方法的返回值都是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、讀寫分離的配置類。也就是分別創建讀寫的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、分別創建讀寫的mapper文件。我本地分別創建了：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。以上幾部就搞定了讀寫分離的准備工作，接着就可以在controller里調用了。 准備工作完成后，還有重要的一點就是需要在程序入口處排除springboot自動屬性提供的數據源  @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();
    }


}

　　

 

總結

       好了，基本上又是3分鍾就搞定了SpringBoot+MyBatis多數據源或者叫做讀寫分離的工作。那么不知道你又沒有反問我們手動創建的DataSource具體類型是什么呢？ 這里我們在這里只寫了javax.sql.DataSource接口。 我本地用的是springboot 2.0.2 ，當前 DataSourceBuilder 只支持3種類型的數據源： com.zaxxer.hikari.HikariDataSource、org.apache.tomcat.jdbc.pool.DataSource、org.apache.commons.dbcp2.BasicDataSource。可以在DataSourceBuilder類中看到相關代碼。那么現在這種情況因為我們引用的內嵌tomcat，所以我們這里返回的數據源類型是org.apache.tomcat.jdbc.pool.DataSource。 可以用instanceof驗證一下具體的數據源類型。