ssm实现mysql读写分离

用于以后方便查看，借用：https://blog.csdn.net/weixin_43882034/article/details/84996443

1.创建 DyncmicDataSourceHolder 类

package cn.ljs.dyncmic;

import com.alibaba.dubbo.common.utils.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 在读写分离的实现上，
 * Spring为我们提供了路由数据源的AbstractRoutingDataSource抽象类，
 * 我们只需编写一个新的类继承它，
 * 即可在不改变原有的代码的基础上实现读写分离
 */
public class DyncmicDataSourceHolder {
    private static Logger logger= LoggerFactory.getLogger(DyncmicDataSourceHolder.class);

    /**
     * 保证线程安全，使用线程threadlocal
     */
    private static ThreadLocal contextHolder=new ThreadLocal();

    public static final String DB_MASTER="master";

    public static final String DB_SLAVE="slave";

    /**
     * @return java.lang.String
     * @description 获取连接类型
     */
    public static String getDbType(){
        String db=contextHolder.get();
        if (StringUtils.isBlank(db)) {
            db=DB_MASTER;
        }
        return db;
    }

    /**
     * 设置数据源类型
     * @param str
     */
    public static void setDbType(String str){
        logger.debug("使用数据源类型---"+str);
        System.err.println("使用数据源类型---"+str);
        contextHolder.set(str);
    }

    /**
     * 清理连接类型
     */
    public static void clearDaType(){
        contextHolder.remove();
    }
}

2.创建 DynamicDataSource，继承AbstractRoutingDataSource

package cn.ljs.dyncmic;

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

public class DynamicDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return DyncmicDataSourceHolder.getDbType();
    }
}

3 创建DyncmicDataSourceInterceptor，mybatis拦截器

package cn.ljs.dyncmic;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.executor.keygen.SelectKeyGenerator;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.transaction.support.TransactionSynchronizationManager;

import java.util.Locale;
import java.util.Properties;

/**
 * 创建DyncmicDataSourceInterceptor，mybatis拦截器
 */
@Intercepts({@Signature(type = Executor.class, method = "update", args = {MappedStatement.class,
        Object.class}),
        @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class,
                RowBounds.class, ResultHandler.class})})
public class DyncmicDataSourceInterceptor implements Interceptor {

    private static Logger logger = LoggerFactory.getLogger(DyncmicDataSourceInterceptor.class);
    // 写操作的正则表达式
    private static final String REGEX = ".*insert\\u0020.*||.*delete\\u0020|.*update\\u0020.*";

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // 判断方法是否是被事务管理的
        boolean synchronizationAction = TransactionSynchronizationManager.isActualTransactionActive();
        //获取sql 中的参数
        Object[] objects = invocation.getArgs();
        MappedStatement mappedStatement = (MappedStatement) objects[0];
        //数据源key
        String lookupKey = DyncmicDataSourceHolder.DB_MASTER;
        if (!synchronizationAction) {
            // 读方法
            if (mappedStatement.getSqlCommandType().equals(SqlCommandType.SELECT)) {
                //selectKey为自增id查询主键（SELECT LAST_INSERT_ID）方法
                if (mappedStatement.getId().contains(SelectKeyGenerator.SELECT_KEY_SUFFIX)) {
                    lookupKey = DyncmicDataSourceHolder.DB_MASTER;
                } else {
                    //获取sql 语句
                    BoundSql boundSql = mappedStatement.getSqlSource().getBoundSql(objects[1]);
                    String sql = boundSql.getSql().toLowerCase(Locale.CHINA).replace("\\t\\n\\r", " ");
                    if (sql.matches(REGEX)) {//insert、update、delete
                        lookupKey = DyncmicDataSourceHolder.DB_MASTER;
                    } else {//select
                        lookupKey = DyncmicDataSourceHolder.DB_SLAVE;
                    }
                }
            }
        } else {
            lookupKey = DyncmicDataSourceHolder.DB_MASTER;
        }
        logger.debug("设置方法[{}] use [{}] Strategy,SqlCommandType [{}]...", mappedStatement.getId(),
                lookupKey, mappedStatement.getSqlCommandType().name());
        DyncmicDataSourceHolder.setDbType(lookupKey);
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        //Executor表示含有增删改查的操作 的对象
        if (target instanceof Executor) {
            //有增删改查的操作,就调用拦截方法
            return Plugin.wrap(target, this);
        } else {
            //无增删改查的操作。不做处理
            return target;
        }
    }

    @Override
    public void setProperties(Properties properties) {

    }
}

4.修改mybatis-config，引入拦截器

<?xml version="1.0" encoding="UTF-8"?>
DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">


    
        
         
        
        
    

    
    
        <package name="cn.ljs.entity" />
    
    
    
        
    

5，修改mybatis配置文件，

<?xml version="1.0" encoding="UTF-8"?>

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

 
     
    
    
    class="com.alibaba.druid.pool.DruidDataSource"
        init-method="init"  destroy-method="close">
        

        
        
        
        
        
        
        
        

        
        

        
        

        
        

        
        
        
        

        
        
        
        
        
        
    

    class="com.alibaba.druid.pool.DruidDataSource"
          init-method="init"  destroy-method="close">
        
        
        
        
        
        
        
        

        
        

        
        

        
        

        
        
        
        

        
        
        

        
        
    

    
    class="cn.ljs.dyncmic.DynamicDataSource">
        
            
        
    
    
    class="org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy">
        
            
        
    

    
    class="org.mybatis.spring.SqlSessionFactoryBean">
        
        
        
        
        
    
    
    
    class="org.mybatis.spring.mapper.MapperScannerConfigurer">