1.功能介绍

在实际的开发中，同一个项目中使用多个数据源是很常见的场景。最近在学习的过程中使用注解的方式实现了一个Springboot项目多数据源的功能。具体实现方式如下。

2.在application.properties中添加多数据源配置

添加多个数据源和mapper文件路径配置，此配置用于基于java的配置数据源中使用。

#数据库配置

spring.datasource.demo.user.url=jdbc:mysql://xxx.xx.xx.xx:3306/demo-user

spring.datasource.demo.user.username=xxxx

spring.datasource.demo.user.password=xxxx

spring.datasource.demo.user.driver-class-name=com.mysql.jdbc.Driver

spring.datasource.demo.server.url=jdbc:mysql://xxx.xx.xx.xx:3306/springbootdemo

spring.datasource.demo.server.username=xxxx

spring.datasource.demo.server.password=xxxx

spring.datasource.demo.server.driver-class-name=com.mysql.jdbc.Driver

#mapper文件的路径

mybatis.demo.server.mapper-location=classpath*:mapper/demo-server/*.xml

mybatis.demo.user.mapper-location=classpath*:mapper/demo-user/*.xml

3.基于java的方式实现数据库配置

配置类图如下：

其中DemoUserDbConfig类源代码如下：

其中Configuration注解表识此类为Spring的配置类。

MapperScan注解中的basePackages、annotationClass、sqlSessionTemplateRef用于配置此数据库链接扫描com.example包中所有注解为DemoUserMapper的接口。

@Configuration

@MapperScan(basePackages = {"com.example"},annotationClass = DemoUserMapper.class,

sqlSessionTemplateRef = "demoUserTemplate")

public class DemoUserDbConfig extends AbstractDbConfig {

@Value("${spring.datasource.demo.user.url}")

private String url;

@Value("${spring.datasource.demo.user.username}")

private String userName;

@Value("${spring.datasource.demo.user.password}")

private String password;

@Value("${spring.datasource.demo.user.driver-class-name}")

private String driveClassName;

@Value(value = "${mybatis.demo.user.mapper-location}")

private String mapperLocation;

@Bean(name = "demoUser")

public DataSource secondaryDataSource() {

return dataSourceFactory(driveClassName, url, userName, password);

}

@Bean(name = "demoUserTemplate")

public SqlSessionTemplate demoUserSqlTemplate() throws Exception {

return new SqlSessionTemplate((sqlSessionFactory(secondaryDataSource(), mapperLocation)));

}

@Bean

@Qualifier("demoUserTransaction")

public PlatformTransactionManager demoUserTransaction() {

return new DataSourceTransactionManager(secondaryDataSource());

}

}

其中AbstractDatasource设置了通用的方法，源代码如下：

public abstract class AbstractDbConfig {

protected SqlSessionFactory sqlSessionFactory(DataSource dataSource, String mapperLocation) throws Exception {

SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();

factoryBean.setDataSource(dataSource);

ResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver();

Resource[] resource= resourceResolver.getResources(mapperLocation);

factoryBean.setMapperLocations(resource);

return factoryBean.getObject();

}

protected DataSource dataSourceFactory(String driveClassName, String url, String userName, String password){

DruidDataSource datasource = new DruidDataSource();

datasource.setDriverClassName(driveClassName);

datasource.setUrl(url);

datasource.setUsername(userName);

datasource.setPassword(password);

datasource.setMaxActive(20);

datasource.setInitialSize(20);

return datasource;

}

}

使用相同的方法定义其他数据源。

4.定义接口和mapper文件

分别定义连接demo-user数据库和springbootdemo数据库的mapper文件。连接demo-user数据库的接口如下，使用DemoUserMapper注解表识。

@DemoUserMapper

public interface UserDao {

/**

* 返回所有的dictionary列表

*

* @return 所有的dictionary列表

*/

List list();

}

mapper文件如下：

SELECT `name` FROM `user`

定义读取springbootdemo数据库的接口，代码如下。使用DemoServerMapper注解表识

@DemoServerMapper

public interface DictionaryDao {

/**

* 返回所有的dictionary列表

*

* @return 所有的dictionary列表

*/

List list();

/**

* 查询此key下的所有子节点

*

* @param key 数据字典key

* @return 返回key所有的子节点列表

*/

List listChildrenByKey(String key);

/**

* 插入数据到数据库

*

* @param dictionary

*/

void insert(Dictionary dictionary);

}

mapper文件代码如下：

SELECT * FROM `dictionary`

SELECT * FROM dictionary where parent_id= (select id from dictionary where dict_key= #{key})

delete from dictionary where id = #{id}

INSERT INTO `dictionary`(`dict_key`,`dict_value`,`parent_id`,`description`)

VALUES(#{dictKey}, #{dictValue}, #{parentId}, #{description})

5.定义注解

定义DemoUserMapper和DemoServerMapper注解，分别作为使用demo-user和springbootdemo数据库的表识。

定义代码如下：

@Documented

@Retention(RetentionPolicy.RUNTIME)

@Target(ElementType.TYPE)

@Component

@Mapper

public @interface DemoServerMapper {

/**

* The value may indicate a suggestion for a logical component name,

* to be turned into a Spring bean in case of an autodetected component.

* @return the suggested component name, if any (or empty String otherwise)

*/

String value() default "";

}

@Documented

@Retention(RetentionPolicy.RUNTIME)

@Target(ElementType.TYPE)

@Component

@Mapper

public @interface DemoUserMapper {

/**

* The value may indicate a suggestion for a logical component name,

* to be turned into a Spring bean in case of an autodetected component.

* @return the suggested component name, if any (or empty String otherwise)

*/

String value() default "";

}

6.使用单元测试验证配置

编写单元测试代码如下：

@RunWith(SpringRunner.class)

@SpringBootTest

public class MultiDatasourceApplicationTests {

@Autowired

private DictionaryDao dictionaryDao;

@Autowired

private UserDao userDao;

@Test

public void contextLoads() {

System.out.println(dictionaryDao.list());

System.out.println("===================");

System.out.println(userDao.list());

}

}