JAVAEE之Spring学习(三)---通过aop切面实现事务处理

需求：通过切面给项目中的service添加事务处理，让数据库表1添加用户失败后回滚，表2无法添加数据

思想：通过aop切面拦截service下的reg()方法，在拦截之前开启事务再进行dao调用，进行事务处理

需要注意的地方：在spring方式下获得到的datasource中的getconnection方法还没有进行拦截，在dao层，是通过queryrunner自动调用getconnection()进行提交，所以要将getconnection()做成单线程形式

service：

package cn.hncu.stud.service;

import java.sql.SQLException;

import cn.hncu.stud.dao.IStudaoa;
import cn.hncu.stud.domain.User;

public class serviceimpl implements IStudentService {
IStudaoa dao1 = null;
IStudaoa dao2 = null;

public IStudaoa getDao1() {
return dao1;
}

public void setDao1(IStudaoa dao1) {
this.dao1 = dao1;
}

public IStudaoa getDao2() {
return dao2;
}

public void setDao2(IStudaoa dao2) {
this.dao2 = dao2;
}

// 注入
@Override
public void reg(User user) throws SQLException {
dao1.reg(user);
dao2.reg(user);
}

}

web.xml:将Spring容器放入servletContext中

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name></display-name>

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
<!-- 如果有路径要用"/"开始 -->
classpath:beans.xml,
/WEB-INF/applicationContext.xml
</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
<servlet-name>StudServlet</servlet-name>
<servlet-class>cn.hncu.stud.servlet.StudServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>StudServlet</servlet-name>
<url-pattern>/StudServlet</url-pattern>
</servlet-mapping>

<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

servlet:通过ApplicationContext ctx = WebApplicationContextUtils.getWebApplicationContext(getServletContext());获取spring容器

package cn.hncu.stud.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import cn.hncu.stud.domain.User;
import cn.hncu.stud.service.IStudentService;

public class StudServlet extends HttpServlet {
private IStudentService service = null;

@Override
public void init() throws ServletException {
// 获取web项目中的spring容器
ApplicationContext ctx = WebApplicationContextUtils
.getWebApplicationContext(getServletContext());
service = ctx.getBean("service", IStudentService.class);
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String name = request.getParameter("name");
User user = new User();
user.setName(name);
try {
service.reg(user);
request.getSession().setAttribute("user", user);
request.getRequestDispatcher("/jsps/show.jsp").forward(request,
response);
} catch (SQLException e) {
e.printStackTrace();
}
}

}

applicationContext:用于配置dataSource和拦截getconnection的公共Spring容器配置文件

<?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:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"

xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd ">
<bean
class="org.springframework.aop.framework.autoproxy.DefaultAdvisorAutoProxyCreator">
</bean>
<!-- 切面=切点+通知 -->
<bean id="advisor"
class="org.springframework.aop.aspectj.AspectJExpressionPointcutAdvisor">
<!-- 切点 -->
<property name="expression">
<value>
execution( void cn.hncu.stud..serviceimpl.reg(..) )
</value>
</property>
<property name="advice">
<bean class="cn.hncu.stud.utils.AroundAdvice">
<property name="data" ref="dataSource"></property>
</bean>
</property>
</bean>

<!-- 切面=切点+通知 -->
<bean id="advisor1"
class="org.springframework.aop.aspectj.AspectJExpressionPointcutAdvisor">
<!-- 切点 -->
<property name="expression">
<value>execution(* *..*.getConnection())
</value>
</property>
<property name="advice">
<bean class="cn.hncu.stud.utils.ConAdvice">
</bean>
</property>
</bean>

<context:property-placeholder location="WEB-INF/conf/jdbc.properties" />
<bean id="dataSource"
class="org.springframework.jdbc.datasource.SimpleDriverDataSource">
<property name="driverClass" value="${driver}">
</property>
<property name="url" value="${url}"></property>
<!-- ${username}是系统默认的变量-->
<property name="username" value="${uname}"></property>
<property name="password" value="${password}"></property>
</bean>

</beans>

用于拦截getconnection方法的切面：

package cn.hncu.stud.utils;

import java.lang.reflect.Method;
import java.sql.Connection;

import javax.sql.DataSource;

import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodProxy;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

public class ConAdvice implements MethodInterceptor {
private ThreadLocal<Connection> t1 = new ThreadLocal<Connection>();

DataSource data = null;

public DataSource getData() {
return data;
}

public void setData(DataSource data) {
this.data = data;
}

@Override
public Object invoke(MethodInvocation inv) throws Throwable {
Connection con = t1.get();
if (con == null) {
// 往本地线程池中放一个被屏蔽掉close()方法的con对象
final Connection con0 = ((Connection) inv.proceed());// 当前被拦截的是getconnection返回的是一个con
// 对con0进行代理(屏蔽close())
Callback callback = new net.sf.cglib.proxy.MethodInterceptor() {

@Override
public Object intercept(Object proxiedObj, Method method,
Object[] args, MethodProxy proxy) throws Throwable {
if (method.getName().equals("close")) {
return null;
}
return method.invoke(con0, args);
}
};
// 生成代理后的对象
con = (Connection) Enhancer.create(Connection.class, callback);
t1.set(con);// 把代理后的对象放进去
}
return con;
}
}

beans.xml:用于配置stud模块下的类的关联

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/aop" 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"> 
<bean id="studDao" class="cn.hncu.stud.dao.IStuJDBCDAO">
<property name="dataSource" ref="dataSource"></property>
</bean>
<bean id="studDao2" class="cn.hncu.stud.dao.IStuJDBCDAO2">
<property name="dataSource" ref="dataSource"></property>
</bean>
<bean id="service" class="cn.hncu.stud.service.serviceimpl">
<property name="dao1" ref="studDao"></property>
<property name="dao2" ref="studDao2"></property>
</bean>
</beans>

AroundAdvice:进行service类的拦截：

package cn.hncu.stud.utils;

import java.sql.Connection;

import javax.sql.DataSource;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class AroundAdvice implements MethodInterceptor, ApplicationContextAware {
ApplicationContext ctx = null;
DataSource data = null;

public DataSource getData() {
return data;
}

public void setData(DataSource data) {
this.data = data;
}

@Override
public Object invoke(MethodInvocation invocation) throws Throwable {
Connection con = data.getConnection();
con.setAutoCommit(false);
System.out.println("开启事务");
// 放行
try {
Object returnValue = invocation.proceed();
con.commit();
return returnValue;
} catch (Exception e) {
con.rollback();
System.out.println("事务回滚");
} finally {
con.setAutoCommit(true);
}
return null;
}

@Override
public void setApplicationContext(ApplicationContext ctx)
throws BeansException {
this.ctx = ctx;
}

}

这样就成功通过spring实现数据库的事务处理