AOP中关键性概念
连接点(Joinpoint):程序执行过程中明确的点,如方法的调用,或者异常的抛出.
目标(Target):被通知(被代理)的对象
注1:完成具体的业务逻辑
通知(Advice):在某个特定的连接点上执行的动作,同时Advice也是程序代码的具体实现,例如一个实现日志记录的代码(通知有些书上也称为处理)
注2:完成切面编程
代理(Proxy):将通知应用到目标对象后创建的对象(代理=目标+通知),
例子:外科医生+护士
注3:只有代理对象才有AOP功能,而AOP的代码是写在通知的方法里面的
切入点(Pointcut):多个连接点的集合,定义了通知应该应用到那些连接点。
(也将Pointcut理解成一个条件 ,此条件决定了容器在什么情况下将通知和目标组合成代理返回给外部程序)
适配器(Advisor):适配器=通知(Advice)+切入点(Pointcut)
如何实现AOP
目标对象只负责业务逻辑代码
通知对象负责AOP代码,这二个对象都没有AOP的功能,只有代理对象才有
1. AOP
即面向切面编程
2. AOP带来的好处
让我们可以 “专心做事”
案例:
public void doSameBusiness (long lParam,String sParam){
// 记录日志
log.info("调用 doSameBusiness方法,参数是:"+lParam);
// 输入合法性验证
if (lParam<=0){
throws new IllegalArgumentException("xx应该大于0");
}
if (sParam==null || sParam.trim().equals("")){
throws new IllegalArgumentException("xx不能为空");
}
// 异常处理
try{ ...
}catch(...){
}catch(...){
}
// 事务控制
tx.commit();
}
3 工具类org.springframework.aop.framework.ProxyFactoryBean用来创建一个代理对象,在一般情况下它需要注入以下三个属性:
proxyInterfaces:代理应该实现的接口列表(List)
interceptorNames:需要应用到目标对象上的通知Bean的名字。(List)
target:目标对象 (Object)
4. 前置通知(org.springframework.aop.MethodBeforeAdvice):在连接点之前执行的通知()
案例:在购书系统当中使用AOP方式实现日志系统
下面我们来编写代码:
先导入pom.xml依赖
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>T226_huang</groupId> <artifactId>T226_spring2_aop</artifactId> <packaging>war</packaging> <version>0.0.1-SNAPSHOT</version> <name>T226_spring2_aop Maven Webapp</name> <url>http://maven.apache.org</url> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.44</version> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>4.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>4.3.10.RELEASE</version> </dependency> </dependencies> <build> <finalName>T226_spring2_aop</finalName> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.7.0</version> <configuration> <source>1.8</source> <target>1.8</target> <encoding>UTF-8</encoding> </configuration> </plugin> </plugins> </build> </project>
工具类:
IbookBiz
package com.huang.aop.biz; public interface IBookBiz { // 购书 public boolean buy(String userName, String bookName, Double price); // 发表书评 public void comment(String userName, String comments); }
BookBizimpl
package com.huang.aop.biz.impl; import com.huang.aop.biz.IBookBiz; import com.huang.aop.ex.PriceException; public class BookBizImpl implements IBookBiz { public BookBizImpl() { super(); } public boolean buy(String userName, String bookName, Double price) { // 通过控制台的输出方式模拟购书 if (null == price || price <= 0) { throw new PriceException("book price exception"); } System.out.println(userName + " buy " + bookName + ", spend " + price); return true; } public void comment(String userName, String comments) { // 通过控制台的输出方式模拟发表书评 System.out.println(userName + " say:" + comments); } }
异常处理类:
package com.huang.aop.ex; public class PriceException extends RuntimeException { public PriceException() { super(); } public PriceException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) { super(message, cause, enableSuppression, writableStackTrace); } public PriceException(String message, Throwable cause) { super(message, cause); } public PriceException(String message) { super(message); } public PriceException(Throwable cause) { super(cause); } }
前置通知
实现org.springframework.aop.MethodBeforeAdvice接口
买书、评论前加系统日志
package com.huang.aop.advice; import java.lang.reflect.Method; import java.util.Arrays; import org.springframework.aop.MethodBeforeAdvice; /** * 买书、评论前加系统日志 * @author Admin * */ public class MyMethodBeforeAdvice implements MethodBeforeAdvice { @Override public void before(Method method, Object[] args, Object target) throws Throwable { String clzName=target.getClass().getName(); String methodName=method.getName(); String params=Arrays.toString(args); System.out.println("[买书、评论前加系统日志]:"+clzName+"."+methodName+"("+params+")"); } }
后置通知
实现org.springframework.aop.AfterReturningAdvice接口
买书返利(存在bug)
package com.huang.aop.advice; import java.lang.reflect.Method; import java.util.Arrays; import org.springframework.aop.AfterReturningAdvice; /** * 买书返利(存在bug) * @author Admin * */ public class MyAfterReturningAdvice implements AfterReturningAdvice { @Override public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable { String clzName=target.getClass().getName(); String methodName=method.getName(); String params=Arrays.toString(args); System.out.println("[买书返利的后置通知]:"+clzName+"."+methodName+"("+params+")"+" 目标对象方法调用后的返回值"+returnValue); } }
环绕通知
org.aopalliance.intercept.MethodInterceptor
类似拦截器,会包括切入点,目标类前后都会执行代码
package com.huang.aop.advice; import java.util.Arrays; import org.aopalliance.intercept.MethodInterceptor; import org.aopalliance.intercept.MethodInvocation; public class MyMethodInterceptor implements MethodInterceptor { @Override public Object invoke(MethodInvocation invocation) throws Throwable { String clzName=invocation.getThis().getClass().getName(); String methodName=invocation.getMethod().getName(); String params=Arrays.toString(invocation.getArguments()); System.out.println("【环绕通知】:"+clzName+"."+methodName+"("+params+")"); Object returnValue=invocation.proceed(); System.out.println("【环绕通知】 目标对象方法调用后的返回值"+returnValue); return returnValue; } }
异常通知
org.springframework.aop.ThrowsAdvice
出现异常执行系统提示,然后进行处理。价格异常为例
package com.huang.aop.advice; import org.springframework.aop.ThrowsAdvice; import com.huang.aop.ex.PriceException; /** * 异常通知 * @author Administrator * 案例:张三向李四转账 * biz.transfer(user1,user2) * UserDao.update(user1) * UserDao.update(user2) */ public class MyThrowsAdvice implements ThrowsAdvice { public void afterThrowing( PriceException ex ) { System.out.println("价格输入有误,购买失败,请重新输入!!!"); } }
过滤通知(适配器)
org.springframework.aop.support.RegexpMethodPointcutAdvisor
处理买书返利的bug
<?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" default-autowire="byType" xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd"> <bean class="com.huang.ioc.biz.impl.UserBizImpl2" id="userBiz"></bean> <bean class="com.huang.ioc.web.UserAction" id="xxx"> <!-- 构造注入用constructor-arg标签 --> <constructor-arg name="uname" value="ls"></constructor-arg> <constructor-arg name="age" value="22"></constructor-arg> <property name="hobby" > <list> <value>充钱使你强大</value> <value>RMB</value> <value>腾讯</value> </list> </property> </bean> <bean class="com.huang.ioc.web.OrderAction" id="ttt"> <!-- <property name="userBiz" ref="userBiz"></property> --> </bean> <!-- AOP --> <!-- 目标对象 --> <bean id="bookBiz" class="com.huang.aop.biz.impl.BookBizImpl"></bean> <!-- 通知 --> <bean id="myBefore" class="com.huang.aop.advice.MyMethodBeforeAdvice"></bean> <bean id="myAfter" class="com.huang.aop.advice.MyAfterReturningAdvice"></bean> <bean id="myInterceptor" class="com.huang.aop.advice.MyMethodInterceptor"></bean> <bean id="myThrowsAdvice" class="com.huang.aop.advice.MyThrowsAdvice"></bean> <bean id="myAfter2" class="org.springframework.aop.support.RegexpMethodPointcutAdvisor"> <property name="advice" ref="myAfter"></property> <property name="pattern" value=".*bug"></property> </bean> <!-- 有代 理工厂来组装目标对象及通知 --> <bean id="bookProxy" class="org.springframework.aop.framework.ProxyFactoryBean"> <property name="target" ref="bookBiz"></property> <property name="proxyInterfaces"> <list> <value>com.huang.aop.biz.IBookBiz</value> </list> </property> <property name="interceptorNames"> <list> <value>myBefore</value> <!-- <value>myAfter</value> --> <value>myAfter2</value> <value>myInterceptor</value> <value>myThrowsAdvice</value> </list> </property> </bean> </beans>
运行结果: