mysql分库，动态数据库切换

分库分表：解决思路，Dao-->ORM--->JDBC-->Proxy-->Server
1分库
在Dao层进行选择数据库
 package org.springframework.jdbc.datasource.lookup下的
AbstractRoutingDataSource实现多数据源切换

Dao层数据源切换：

package com.example.demo.multdatasource;


import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;

/**
 * 多数据源切面
 */
@Aspect
@Slf4j
@Component
public class DataSourceAspect {

    @Pointcut("@annotation( com.example.demo.multdatasource.TargetDataSource)")
    public void pointcut() {

    }
    @Around("pointcut()")
    public Object Around(ProceedingJoinPoint proceedingJoinPoint) {
        MethodSignature methodSignature = (MethodSignature)proceedingJoinPoint.getSignature();
        Method method = methodSignature.getMethod();
        TargetDataSource annotation = method.getAnnotation(TargetDataSource.class);
        if(annotation==null){
            //目标方法上没有注解，设置默认为第一个数据源
            MyAbstractDataSource.setDtaSource(DataSourceNames.FIRST);
        }else{
            //目标方法伤有数据源，就设置数据源为注解里的数据源
            MyAbstractDataSource.setDtaSource(annotation.name());
        }
        try {
            return  proceedingJoinPoint.proceed();
        } catch (Throwable throwable) {
            throwable.printStackTrace();
        }finally {
            MyAbstractDataSource.clearDataSource();
        }
        return null;
    }
}

package com.example.demo.multdatasource;

/**
 * 多数据源选择设置处，也可以设置枚举
 */
public interface DataSourceNames {
       String  FIRST = "FIRST";
       String   SECOND = "SECOND";
}

package com.example.demo.multdatasource;

/**
 * 演示Dao层注解获取
 */
public class MultDatraSourceDao {
    @TargetDataSource(name = DataSourceNames.SECOND)
    public Object getObject(){
        return  null;
    }
}

package com.example.demo.multdatasource;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

import javax.sql.DataSource;
import java.util.Map;

/**
 * 多数据源切换实现
 */
public class MyAbstractDataSource extends AbstractRoutingDataSource {

    private  static  final ThreadLocal<String> CONTEXT_HOLDER=new ThreadLocal<>();

    /**
     * 需要使用哪个数据源的信息以及默认数据源先配置好
     * @param defaultTargetDataSource
     * @param targetDataSources
     */
    public MyAbstractDataSource(DataSource defaultTargetDataSource, Map<Object,Object> targetDataSources) {
        super.setDefaultTargetDataSource(defaultTargetDataSource);
        super.setTargetDataSources(targetDataSources);
        super.afterPropertiesSet();
    }

    @Override
    protected Object determineCurrentLookupKey() {
        return getDataSource();
    }
    public static String getDataSource(){
        return CONTEXT_HOLDER.get();
    }

    public static void  setDtaSource(String dataSource){
        CONTEXT_HOLDER.set(dataSource);
    }
    public static  void clearDataSource(){
        CONTEXT_HOLDER.remove();
    }
}

package com.example.demo.multdatasource;

import java.lang.annotation.*;

/**
 * 数据源注解处
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD,ElementType.TYPE})
public @interface TargetDataSource {
    String name() default "";
}

package com.example.demo.multdatasource;


import com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;


/**
 * 多数据源配置处
 */
@Configuration
public class DynamicDataSourceConfig {

    @Bean
    @ConfigurationProperties("spring.datasource.druid.first")
    public DataSource firstDataSource(){
        return DruidDataSourceBuilder.create().build();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.druid.second")
    public DataSource secondDataSource(){
        return DruidDataSourceBuilder.create().build();
    }

    @Bean
    @Primary
    public MyAbstractDataSource dataSource(DataSource firstDataSource,DataSource secondDataSource){
      Map<Object,Object> targetDataSource=new HashMap<>();
        targetDataSource.put(DataSourceNames.FIRST,firstDataSource);
        targetDataSource.put(DataSourceNames.SECOND,secondDataSource);
        return new MyAbstractDataSource(firstDataSource,targetDataSource);
    }
}