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spring+spring mvc +mybatis+druid 实现数据库主从分离

2017-11-02 14:10 459 查看

本文是基于:spring+spring mvc +mybatis+druid为基础框架，实现mysql数据库主从分离.

mysql 主从配置（超简单）http://369369.blog.51cto.com/319630/790921/

第一步:基于java annotation(注解)并通过spring aop 实现动态数据源动态选择

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package com.wlsq.util;

import java.lang.annotation.ElementType;
import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
/**
* RUNTIME
* 编译器将把注释记录在类文件中，在运行时 VM 将保留注释，因此可以反射性地读取。
* @author yangGuang
*
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface DataSource {
    String value();
}

第二步：实现spring 提供 AbstractRoutingDataSource 类实现数据源设置
spring AbstractRoutingDataSource类介绍：http://www.cnblogs.com/surge/p/3582248.html

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package com.wlsq.util;

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

public class ChooseDataSource extends AbstractRoutingDataSource  {
    /**
     * 获取与数据源相关的key
     * 此key是Map<String,DataSource> resolvedDataSources 中与数据源绑定的key值
     * 在通过determineTargetDataSource获取目标数据源时使用
     */
    @Override
    protected Object determineCurrentLookupKey() {
        // TODO Auto-generated method stub
        return HandleDataSource.getDataSource();
    }

}

第三步：利用ThreadLocal 解决数据源设置线程安全性问题

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package com.wlsq.util;

/**
* 保存当前线程数据源的key
* @author
* @version 1.0
*
*/
public class HandleDataSource {
    public static final ThreadLocal<String> holder = new ThreadLocal<String>();

    /**
     * 绑定当前线程数据源路由的key
     * @param key
     */
    public static void putDataSource(String datasource) {
        holder.set(datasource);
    }

    /**
     * 获取当前线程的数据源路由的key
     * @return
     */
    public static String getDataSource() {
        return holder.get();
    }
}

第四步: 定义一个数据源切面类，通过aop 实现访问，在spring 文件中进行相关的配置工作。

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package com.wlsq.util;


import java.lang.reflect.Method;
import org.aspectj.lang.JoinPoint;

import org.aspectj.lang.reflect.MethodSignature;


/**
* 执行dao方法之前的切面
* 获取datasource对象之前往HandleDataSource中指定当前线程数据源路由的key
* @author Administrator
*
*/
public class DataSourceAspect {


    /**
     * 在dao层方法之前获取datasource对象之前在切面中指定当前线程数据源路由的key
     */
     public void before(JoinPoint point)
        {


             Object target = point.getTarget();
             System.out.println(target.toString());
             String method = point.getSignature().getName();
             System.out.println(method);
             Class<?>[] classz = target.getClass().getInterfaces();
             Class<?>[] parameterTypes = ((MethodSignature) point.getSignature())
                     .getMethod().getParameterTypes();
             try {
                 Method m = classz[0].getMethod(method, parameterTypes);
                 System.out.println(m.getName());
                 if (m != null && m.isAnnotationPresent(DataSource.class)) {
                     DataSource data = m.getAnnotation(DataSource.class);
                     System.out.println("用户选择数据库库类型："+data.value());
                     HandleDataSource.putDataSource(data.value());
                 }

             } catch (Exception e) {
                 e.printStackTrace();
             }
        }
}

第五步：配置spring-mybatis.xml 配置文件

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                        http://www.springframework.org/schema/context
                        http://www.springframework.org/schema/context/spring-context-3.1.xsd
                        http://www.springframework.org/schema/tx
                        http://www.springframework.org/schema/tx/spring-tx-3.1.xsd
                        http://www.springframework.org/schema/aop
                        http://www.springframework.org/schema/aop/spring-aop-3.1.xsd
                        http://www.springframework.org/schema/mvc
                        http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">


    
    <tx:annotation-driven  transaction-manager="transactionManager"/>

    <context:component-scan base-package="com.wlsq">
        <context:exclude-filter type="annotation"
            expression="org.springframework.stereotype.Controller" />
    </context:component-scan>

    
    <bean id="propertyConfigurer"
        class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location" value="classpath:jdbc.properties" />
    </bean>



    <bean id="readDataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
    
      <property name="url" value="jdbc:mysql://localhost:3306/wlsq" />
      <property name="username" value="root" />
      <property name="password" value="123456" />

      
      <property name="initialSize" value="1" />
      <property name="minIdle" value="1" />
      <property name="maxActive" value="20" />

      
      <property name="maxWait" value="60000" />

      
      <property name="timeBetweenEvictionRunsMillis" value="60000" />

      
      <property name="minEvictableIdleTimeMillis" value="300000" />

      <property name="validationQuery" value="SELECT 'x'" />
      <property name="testWhileIdle" value="true" />
      <property name="testOnBorrow" value="false" />
      <property name="testOnReturn" value="false" />

      
      <property name="poolPreparedStatements" value="true" />
      <property name="maxPoolPreparedStatementPerConnectionSize" value="20" />

      
      <property name="filters" value="stat" />
    </bean>

    <bean id="writeDataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
    
      <property name="url" value="jdbc:mysql://localhost:3306/wlsqs" />
      <property name="username" value="root" />
      <property name="password" value="123456" />

      
      <property name="initialSize" value="1" />
      <property name="minIdle" value="1" />
      <property name="maxActive" value="20" />

      
      <property name="maxWait" value="60000" />

      
      <property name="timeBetweenEvictionRunsMillis" value="60000" />

      
      <property name="minEvictableIdleTimeMillis" value="300000" />

      <property name="validationQuery" value="SELECT 'x'" />
      <property name="testWhileIdle" value="true" />
      <property name="testOnBorrow" value="false" />
      <property name="testOnReturn" value="false" />

      
      <property name="poolPreparedStatements" value="true" />
      <property name="maxPoolPreparedStatementPerConnectionSize" value="20" />

      
      <property name="filters" value="stat" />
    </bean>

    <bean id="dataSource" class="com.wlsq.util.ChooseDataSource">
        <property name="targetDataSources">
          <map key-type="java.lang.String">
              
             <entry key="write" value-ref="writeDataSource"/>
             
             <entry key="read" value-ref="readDataSource"/>
          </map>
        </property>
        <property name="defaultTargetDataSource" ref="readDataSource"/>

    </bean>




    
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        
        <property name="mapperLocations" value="classpath:com/wlsq/mapper/*.xml"></property>
    </bean>

    
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.wlsq.dao" />
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
    </bean>

    
    <bean id="transactionManager"
        class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
    </bean>


     
    <bean id="dataSourceAspect" class="com.wlsq.util.DataSourceAspect" />
    <aop:config proxy-target-class="true">
        <aop:aspect id="dataSourceAspect" ref="dataSourceAspect" order="1">
            <aop:pointcut id="tx" expression="execution(* com.wlsq.service..*.*(..)) "/>
            <aop:before pointcut-ref="tx" method="before" />
        </aop:aspect>
    </aop:config>








</beans>

第六步：使用@DataSource 标签，动态选择读写数据库

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package com.wlsq.service;

import java.util.List;
import java.util.Map;

import org.apache.ibatis.annotations.Param;

import com.wlsq.model.News;
import com.wlsq.model.User;
import com.wlsq.util.DataSource;

public interface IUserMapperService {


    int deleteByPrimaryKey(Integer userid);

    int insert(User record);

    int insertSelective(User record);

    User selectByPrimaryKey(Integer userid);

    int updateByPrimaryKeySelective(User record);

    int updateByPrimaryKey(User record);

    List<User> selectByObject (User record);

    @DataSource("read")
    public List<User> selectObject (User record);

    @DataSource("write")
    public List<News> selectAllUsers(@Param("maps") Map<String, Object> maps);

    @DataSource("write")
    public int selectCountUsers();
}

学习总结：
第一个错误：Could not open JDBC Connection for transaction; nested exception is java.lang.IllegalStateException: Cannot determine
target DataSource for lookup key [null] 找不到数据源错误

解决办法：事务管理配置一定要配置在,往HandlerDataSource中注入数据源key之前.

第二个错误：spring aop 实现动态数据源选择，但有时存在数据源切换不及时，导致数据查询错误。

解决办法：调整aop 执行排序级别

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<aop:aspect id="dataSourceAspect" ref="dataSourceAspect" order="1">

转自：http://blog.csdn.net/zhouzhiwengang/article/details/51087920

其他参考：http://blog.csdn.net/jiawenbo89/article/details/51891053
http://blog.csdn.net/xtj332/article/details/43953699

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