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

- 日理万妓 2023-10-16 23:24 3阅读 0赞

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/][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

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][http_www.cnblogs.com_surge_p_3582248.html]

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

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。

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

<?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

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

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

[http_369369.blog.51cto.com_319630_790921]: http://369369.blog.51cto.com/319630/790921/
[http_www.cnblogs.com_surge_p_3582248.html]: http://www.cnblogs.com/surge/p/3582248.html