mybatis+spring 实现多数据源(注解版)

需求

系统架构是spring framework +各种组件
项目重构打算使用mybatis 作为orm框架
项目依赖多个数据源、多个数据源需要读写分离
抛弃xml配置，完全注解化

问题

注解扫mapper过程中，一个mapper只能被一个sqlsessiontemplate装载 ,若想实现读写分离需要对每个库表定义不同的读写mapper，然后通过@MapperScan(basePackages = "mybatisSpring.mapper" sqlSessionTemplateRef = "") 分别指定数据源。类似图中样式，basePackages分别指定namespace 与testmapper 然后再指定对应的sqlSessionTemplate。

image.png

上述方式实现和逻辑比较简单，但是太粗糙，写的代码会很多。
理想使用方式 mapper层按库表逻辑划分，与业务逻辑完全剥离。

实现方案

使用AbstractRoutingDataSource进行多数据源管理
使用切面完成数据源的动态切换
直接引用sqlSessionTemplate完成读写操作

show me the code

代码结构

代码结构

annotation 自定义注解
conf java配置文件
dao 封装的dao层服务
mapper mybatis的接口mapper类
model DO层

具体代码

AbstractRoutingDataSource 的实现类，管理项目的所有数据源。

public class MomentRoutingDataSource extends AbstractRoutingDataSource {
    private static final ThreadLocal<DataSourceType> dataSourceHolder = new ThreadLocal<>();

    public static void setDataSource(DataSourceType dataSourceType) {
        dataSourceHolder.set(dataSourceType);
    }

    public static DataSourceType getDataSource() {
        return dataSourceHolder.get();
    }

    public static void clear() {
        dataSourceHolder.remove();
    }

    /**
     * Determine the current lookup key. This will typically be
     * implemented to check a thread-bound transaction context.
     * <p>Allows for arbitrary keys. The returned key needs
     * to match the stored lookup key type, as resolved by the
     * {@link #resolveSpecifiedLookupKey} method.
     */
    @Override
    protected Object determineCurrentLookupKey() {
        return getDataSource();
    }


}

spring 配置文件

@Configuration
@MapperScan(basePackages = "mybatisSpring.mapper" )
@ComponentScan(basePackages = "mybatisSpring")
// 开启切面
@EnableAspectJAutoProxy
public class SqlSessionTemplateConf {

    /**
     * 初始化dataSource
     *
     * @return
     * @throws Exception
     */
    private HikariDataSource getDataSource(String dbname) throws Exception {

        HikariDataSource dataSource = new HikariDataSource();
        String jdbcUrl = String.format("jdbc:mysql://%s:%s/%s?zeroDateTimeBehavior=CONVERT_TO_NULL&autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai"
                , "localhost", 3306, "mpaper_cms2");
        dataSource.setJdbcUrl(jdbcUrl);
        dataSource.setUsername("*******");
        dataSource.setPassword("******");
        dataSource.setMinimumIdle(10);
        dataSource.setMaximumPoolSize(20);
        //等待获取连接时间-默认30s，超过配置阈值抛异常
        dataSource.setConnectionTimeout(500);
        dataSource.setPoolName(dbname);
        return dataSource;
    }


    @Bean
    public DataSource momentRoutingDataSource() throws Exception {
        MomentRoutingDataSource momentRoutingDataSource = new MomentRoutingDataSource();
        Map<Object, Object> targetDataSource = new HashMap<>();
        targetDataSource.put(DataSourceType.CMS_RO, getDataSource("cms_ro"));
        targetDataSource.put(DataSourceType.CMS_RW, getDataSource("cms_rw"));
        momentRoutingDataSource.setTargetDataSources(targetDataSource);
       return momentRoutingDataSource;
    }

    @Bean("momentSqlSessionTemplate")
    public SqlSessionTemplate sqlSessionTemplate(DataSource momentRoutingDataSource) throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(momentRoutingDataSource);
        return new SqlSessionTemplate(factoryBean.getObject());
    }

}

切面实现& 定义注解

@Aspect
@Component
@Order(0)
public class CustomDataSourceAspect {
    // @annotation(mybatisSpring.annotation.DataSource) &&
    @Pointcut(value = "execution( * mybatisSpring.dao..*.*(..))")
    public void pointCut() {

    }

    @Before(value = "pointCut()")
    public void changeDataSource(JoinPoint joinPoint) throws NoSuchMethodException {
        Class<?> aClass = joinPoint.getTarget().getClass();
        //拦截mapper方法
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        Method method = signature.getMethod();
        if (method != null && method.isAnnotationPresent(DataSource.class)) {
            DataSource dataSource = method.getAnnotation(DataSource.class);
            MomentRoutingDataSource.setDataSource(dataSource.type());
            System.out.println("Service Class 数据源切换至--->" + dataSource.type().getValue());
            return;
        }
        //拦截mapper类
        if (aClass.isAnnotationPresent(DataSource.class)) {
            DataSource dataSource = aClass.getAnnotation(DataSource.class);
            MomentRoutingDataSource.setDataSource(dataSource.type());
            System.out.println("Service Class 数据源切换至--->" + dataSource.type().getValue());
            return;
        }

    }

    /**
     * 方法结束后
     */
    @After(value = "pointCut()")
    public void afterReturning() throws Throwable {
        try {
            MomentRoutingDataSource.clear();
            System.out.println("数据源已移除！");
        } catch ( Exception e ) {
            e.printStackTrace();
            System.out.println("数据源移除报错！");
        }

    }
}

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface DataSource {

    DataSourceType type() default DataSourceType.CMS_RO;
}

-dao 层代码

@Service
@DataSource(type = DataSourceType.CMS_RO)
public class NewsTvInfoDao {
    @Autowired
    private SqlSessionTemplate momentSqlSessionTemplate;

    public NewsTvInfo getNewsTvInfo(int id) {
        NewsTvInfoMapper mapper = momentSqlSessionTemplate.getMapper(NewsTvInfoMapper.class);
        return mapper.findByVid(id);
    }

    @DataSource(type = DataSourceType.CMS_RW)
    public NewsTvInfo getNewsTvInfoRw(int id) {
        ActivityMapper mapper = momentSqlSessionTemplate.getMapper(ActivityMapper.class);
        return mapper.findByVid(id);
    }
}

main 入口

public class MybatieSpringMain {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SqlSessionTemplateConf.class);
        // 方法前未添加注解，取类的注解注入的数据源
        NewsTvInfoDao dao = context.getBean(NewsTvInfoDao.class);
        NewsTvInfo newsTvInfo = dao.getNewsTvInfo(9102910);
        System.out.println(newsTvInfo.getBigPic());
         // 方法添加注解，取方法的注解注入的数据源
        NewsTvInfo newsTvInfoRw = dao.getNewsTvInfoRw(9102910);
        System.out.println(newsTvInfoRw.getBigPic());

    }
}

说明

代码未列完整，依赖mybatis ，mybatis-spring 依赖包
切面逻辑中，会先扫描方法后扫描类。因此方法添加的注解的优先级大于类的优先级，因此可以在dao层类的上方添加默认数据源。
@EnableAspectJAutoProxy需要添加此注解