SpringBoot整合MyBatis实现动态数据源切换

本文主要内容

1. 动态数据源实现目标；

2. AbstractRoutingDataSource类分析

3. SpringBoot整合MyBatis动态数据源实现

1. 动态数据源实现目标

项目中存在多个数据源连接，根据不同接口，动态连接不同的数据源DataSources对象，根据不同的业务逻辑操作不同数据源

2. AbstractRoutingDataSource类分析

1.  AbstractRoutingDataSource是由Spring提供的标准数据源

public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {

public abstract class AbstractDataSource implements DataSource {

2.  AbstractRoutingDataSource 类中，配置了多个数据源的Map集合，根据不同的key，取出不同的DataSource ，在获取目标数据源时，调用了this.determineCurrentLookupKey();  获取key，从而拿到对应的DataSource；因此可以实现 determineCurrentLookupKey   方法，操作key，从而动态切换数据源DataSource对象

public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
    @Nullable
    private Map targetDataSources;
    @Nullable
    private Object defaultTargetDataSource;
    private boolean lenientFallback = true;
    private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
    @Nullable
    private Map resolvedDataSources;
    @Nullable
    private DataSource resolvedDefaultDataSource;

    .....

    protected DataSource determineTargetDataSource() {
        Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
        Object lookupKey = this.determineCurrentLookupKey();
        DataSource dataSource = (DataSource)this.resolvedDataSources.get(lookupKey);
        if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
            dataSource = this.resolvedDefaultDataSource;
        }

        if (dataSource == null) {
            throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
        } else {
            return dataSource;
        }
    }

    @Nullable
    protected abstract Object determineCurrentLookupKey();
}

3. SpringBoot整合MyBatis动态数据源实现

 1. 配置多数据源信息

spring.datasource.slave.jdbc-url=jdbc:mysql://localhost:3306/test_mybatis_slave?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=UTC
spring.datasource.slave.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.slave.username=root
spring.datasource.slave.password=123456

spring.datasource.master.jdbc-url=jdbc:mysql://localhost:3306/test_mybatis_master?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=UTC
spring.datasource.master.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.master.username=root
spring.datasource.master.password=123456

2.  定义RoutingDataSourceContext类，绑定线程用于多数据源datasource集合Map的key值生成及取值(基于 ThreadLocal 为基础，存放 key，获取key,移除key)

public class RoutingDataSourceContext {
   static final ThreadLocal threadLocal = new ThreadLocal<>();


   public RoutingDataSourceContext(String key){
      threadLocal.set(key);
   }

   static String getRoutingDataSourceKey(){
      String key = threadLocal.get();
      return key == null ? "master" : key;
   }
}

3.自定义RoutingDataSource 继承 AbstractRoutingDataSource，重写 数据请求之前定义key值方法determineCurrentLookupKey

public class RoutingDataSource extends AbstractRoutingDataSource {
   @Override
   protected Object determineCurrentLookupKey() {
      return RoutingDataSourceContext.getRoutingDataSourceKey();
   }
}

4. 增加数据源配置类DynDataSourceConfiguration，用于创建 多数据源对象(数据源连接中的master,slave)及主数据源（RoutingDataSource）

@Configuration
public class DynDataSourceConfiguration {

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

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



   @Bean
   @Primary
   public DataSource routingDataSource(
         @Autowired @Qualifier("slaveDataSource") DataSource slaveDataSource,
         @Autowired @Qualifier("masterDataSource") DataSource masterDataSource

   ){
      RoutingDataSource routingDataSource = new RoutingDataSource();
      // 封装数据源 map
      Map targetDataSources = new HashMap<>();
      targetDataSources.put("master", masterDataSource);
      targetDataSources.put("slave", slaveDataSource);
      // 将 封装好的数据源 map 放入 RoutingDataSource 中
      routingDataSource.setTargetDataSources(targetDataSources);

      return routingDataSource;
   }
}

5. 自定义注解类 RoutingWith用于指定方法中数据源

@Target(ElementType.METHOD)
@Documented
@Retention(RetentionPolicy.RUNTIME)
public @interface RoutingWith {
   String value();
}

6.通过spring中AOP机制，实现方法调用前设置数据源key

引入aop 功能jar

   org.springframework.boot
   spring-boot-starter-aop

定义RoutingAspect类，针对使用了@RoutingWith注解的方法进行增强

@Component
@Aspect
public class RoutingAspect {

   // AOP增强用于动态获取数据源 针对使用了 自定义的注解 RoutingWith 的方法 名字同参数中的 routingWith
   @Around("@annotation(routingWith)")
   public Object routingWithDataSource(ProceedingJoinPoint proceedingJoinPoint, RoutingWith routingWith) throws Throwable {
         RoutingDataSourceContext routingDataSourceContext = new RoutingDataSourceContext(routingWith.value());
      return proceedingJoinPoint.proceed();
   }
}

7. 需要指定数据源的方法，配置@ RoutingWith注解，指定数据源

@RoutingWith("master")
public List findAllMaster() {
   return userMapper.findAll();
}

@RoutingWith("slave")
public List findAllSlave() {
   return userMapper.findAll();
}