mysql--------多数据源的实现方式

/* 这两个类来对应数据源，而且如果添加数据源也是特别方便的，方便后期
 数据源的扩展 */
public interface DataSources {
    String MASTER_DB = "masterDB";


    String SLAVE_DB = "slaveDB";
}
@Configuration
public class DataSourceConfig {
    //destroy-method="close"的作用是当数据库连接不使用的时候,就把该连接重新放到数据池中,方便下次使用调用.
    @Bean(destroyMethod = "close", name = DataSources.MASTER_DB)
    @ConfigurationProperties(prefix = "spring.datasource")
    public DataSource dataSource(){
        return DataSourceBuilder.create().type(DruidDataSource.class).build();
    }


    @Bean(destroyMethod = "close", name = DataSources.SLAVE_DB)
    @ConfigurationProperties(prefix = "spring.datasource-slave")
    public DataSource dataSourceSlave(){
        return DataSourceBuilder.create().type(DruidDataSource.class).build();
    }
}
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@Configuration
@MapperScan(basePackages = {"com.example.multilpeDataSource.dao"})
public class MybatisConfig {


    @Autowired
    @Qualifier(DataSources.MASTER_DB)
    private DataSource masterDB;


    @Autowired
    @Qualifier(DataSources.SLAVE_DB)
    private DataSource slaveDB;


    @Bean(name = "dynamicDataSource")
    public DataSource dynamicDataSource(){
        DynamicDataSource dynamicDataSource = new DynamicDataSource();
        //设置默认数据源
        dynamicDataSource.setDefaultTargetDataSource(masterDB);


        //map用来存储数据源
        Map<Object , Object> dsMap = new HashMap<>();
        dsMap.put(DataSources.MASTER_DB, masterDB);
        dsMap.put(DataSources.SLAVE_DB, slaveDB);
        dynamicDataSource.setTargetDataSources(dsMap);


        return dynamicDataSource;
    }


    @Bean
    @ConfigurationProperties(prefix = "mybatis")
    public SqlSessionFactoryBean sqlSessionFactoryBean(){
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        //配置数据源，这里是关键配置，如果没有将dynamicDataSource作为数据源则不能实现切换
        sqlSessionFactoryBean.setDataSource(dynamicDataSource());
        return sqlSessionFactoryBean;
    }


}
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/* 注解部分 */
@Retention(RetentionPolicy.RUNTIME)
@Target({
        ElementType.METHOD
})
public @interface RoutingDataSource {


    String value() default DataSources.MASTER_DB;
}
/* AOP部分 */
@Aspect
@Component
public class DynamicDataSourceAspect {


    /**
     * 前置设置dataSource
     * @param joinPoint
     */
    @Before("@annotation(com.example.multilpeDataSource.config.RoutingDataSource)")
    public void beforeSwitchDS(JoinPoint joinPoint){
        MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
        Method method = methodSignature.getMethod();
        /* 默认的数据源我们是从DataSourceContextHolder类中获取 */
        String dataSource = DataSourceContextHolder.DEFAULT_DATASOURCE;
        /* 然后判断我们的注解是否在我们设为切点的方法上 */
        if (method.isAnnotationPresent(RoutingDataSource.class)){
            RoutingDataSource routingDataSource = method.getDeclaredAnnotation(RoutingDataSource.class);
            dataSource = routingDataSource.value();
        }
        DataSourceContextHolder.setDB(dataSource);
    }


    /**
     * 后置清空缓存
     * @param joinPoint
     */
    @After("@annotation(com.example.multilpeDataSource.config.RoutingDataSource)")
    public void afterSwitchDS(JoinPoint joinPoint){
        DataSourceContextHolder.clearDB();
    }


}
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