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使用Spring与JDK动态代理实现事务管理

在现代企业级应用开发中，事务管理是一项关键的技术，它可以保证一系列操作要么全部成功，要么全部失败，从而确保数据的一致性和完整性。Spring框架提供了强大的事务管理能力，但有时为了更细粒度地控制事务边界，我们可能需要自己实现事务管理逻辑。本文将介绍如何结合Spring框架和JDK动态代理技术来实现一个简单的事务管理系统。

引言

在本示例中，我们将创建一个基于Spring框架的应用程序，该程序包含一个账户服务接口（IAccountService），以及其实现类（AccountServiceImp）。为了增强该服务的事务处理能力，我们将创建一个工厂类（ProxyBeanFactory），它会为IAccountService生成一个动态代理对象，该对象能够在调用真实服务方法前后自动开启和提交事务。

XML配置

首先，我们需要配置Spring的bean定义。下面是一个简化版的Spring配置文件示例：

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd"><!-- 数据源配置略 --><!-- QueryRunner配置略 --><!-- 连接工具类配置略 --><!-- 事务工具类配置略 --><!-- 数据访问层配置略 --><!-- 业务逻辑层配置略 --><bean id="proxyService" class="org.example.service.IAccountService" factory-bean="factory" factory-method="createProxy"></bean><bean id="factory" class="org.example.factory.ProxyBeanFactory"><property name="transactionUtil" ref="transactionUtil"></property><property name="toProxyService" ref="service"/></bean><!-- 控制器配置略 --></beans>

如上所示，ProxyBeanFactory将创建一个实现了IAccountService接口的代理对象，并且会在执行业务逻辑之前和之后自动管理事务。

动态代理工厂类

接下来，我们来看一下ProxyBeanFactory类的具体实现：

package org.example.factory;import org.example.service.IAccountService;
import org.example.util.TransactionUtil;import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;public class ProxyBeanFactory {private IAccountService toProxyService;private TransactionUtil transactionUtil;public void setToProxyService(IAccountService toProxyService) {this.toProxyService = toProxyService;}public void setTransactionUtil(TransactionUtil transactionUtil) {this.transactionUtil = transactionUtil;}public IAccountService createProxy() {return (IAccountService) Proxy.newProxyInstance(toProxyService.getClass().getClassLoader(),toProxyService.getClass().getInterfaces(),new InvocationHandler() {@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {Object result = null;try {transactionUtil.beginTx();result = method.invoke(toProxyService, args);transactionUtil.commitTx();} catch (Exception e) {transactionUtil.rollbackTx();} finally {transactionUtil.closeTx();}return result;}});}
}

ProxyBeanFactory类的核心在于createProxy方法，它使用JDK动态代理机制来创建代理对象。当任何IAccountService接口方法被调用时，都会触发InvocationHandler中的invoke方法，从而开启事务、执行业务逻辑并最终提交或回滚事务。

示例代码：

applicationContext.xml：

  <!-- 加载资源文件 --><context:property-placeholder location="classpath:jdbc.properties"></context:property-placeholder><!-- 注入数据源 --><bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"><property name="driverClass" value="${msg1}"/><property name="jdbcUrl" value="${msg2}"/><property name="user" value="${msg3}"/><property name="password" value="${msg4}"/></bean><bean id="queryRunner" class="org.apache.commons.dbutils.QueryRunner"><constructor-arg name="ds" ref="dataSource"/></bean><!-- 连接工具类 --><bean id="connectionUtil" class="org.example.util.ConnectionUtil"><property name="dataSource" ref="dataSource"/></bean><!-- 事务工具类 --><bean id="transactionUtil" class="org.example.util.TransactionUtil"><property name="connectionUtil" ref="connectionUtil"/></bean><bean id="mapperImp" class="org.example.dao.AccountMapperImp"><property name="queryRunner" ref="queryRunner"></property><property name="connectionUtil" ref="connectionUtil"></property></bean><bean id="service" class="org.example.service.AccountServiceImp"><property name="dao" ref="mapperImp"></property></bean><bean id="proxyService" class="org.example.service.IAccountService" factory-bean="factory" factory-method="createProxy"></bean><bean id="factory" class="org.example.factory.ProxyBeanFactory"><property name="transactionUtil" ref="transactionUtil"></property><property name="toProxyService" ref="service"/></bean><bean id="controller" class="org.example.controller.AccountControllerImp"><property name="service" ref="proxyService"></property></bean></beans>

ProxyBeanFactory:

public class ProxyBeanFactory {IAccountService toProxyService;;//装配事务工具类TransactionUtil transactionUtil;public void setAccountServiceImp(IAccountService accountServiceImp) {toProxyService = accountServiceImp;}public void setToProxyService(IAccountService toProxyService) {this.toProxyService = toProxyService;}public void setTransactionUtil(TransactionUtil transactionUtil) {this.transactionUtil = transactionUtil;}public IAccountService getAccountServiceImp() {return toProxyService;}//2.创建代理public IAccountService createProxy(){IAccountService proxy = (IAccountService) Proxy.newProxyInstance(toProxyService.getClass().getClassLoader(), toProxyService.getClass().getInterfaces(), new InvocationHandler() {@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {Object obj = null;try {transactionUtil.beginTx();obj = method.invoke(toProxyService, args);transactionUtil.commitTx();} catch (Exception e) {e.printStackTrace();transactionUtil.rollbackTx();} finally {transactionUtil.closeTx();}return obj;}});return proxy;}
}