SpringAOP模拟实现
文章目录
- 1_底层切点、通知、切面
- 2_切点匹配
- 3_从 @Aspect 到 Advisor
- 1_代理创建器
- 2_代理创建时机
- 3_@Before 对应的低级通知
- 4_静态通知调用
- 1_通知调用过程
- 2_模拟 MethodInvocation
- 5_动态通知调用
1_底层切点、通知、切面
注意点：
- 底层的切点实现
- 底层的通知实现
- 底层的切面实现
- ProxyFactory 用来创建代理
- 如果指定了接口，且 proxyTargetClass = false，使用 JdkDynamicAopProxy
- 如果没有指定接口，或者 proxyTargetClass = true，使用 ObjenesisCglibAopProxy
- 例外：如果目标是接口类型或已经是 jdk 代理，使用 JdkDynamicAopProxy
public class A15 {
public static void main(String[] args) {
/*
两个切面概念
aspect =
通知1(advice) + 切点1(pointcut)
通知2(advice) + 切点2(pointcut)
通知3(advice) + 切点3(pointcut)
...
advisor = 更细粒度的切面，包含一个通知和切点
*/
// 1. 备好切点
AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
pointcut.setExpression("execution(* foo())");
// 2. 备好通知
MethodInterceptor advice = invocation -> {
System.out.println("before...");
Object result = invocation.proceed(); // 调用目标
System.out.println("after...");
return result;
};
// 3. 备好切面
DefaultPointcutAdvisor advisor = new DefaultPointcutAdvisor(pointcut, advice);
/*
4. 创建代理
a. proxyTargetClass = false, 目标实现了接口, 用 jdk 实现
b. proxyTargetClass = false, 目标没有实现接口, 用 cglib 实现
c. proxyTargetClass = true, 总是使用 cglib 实现
*/
Target2 target = new Target2();
ProxyFactory factory = new ProxyFactory();
factory.setTarget(target);
factory.addAdvisor(advisor);
factory.setInterfaces(target.getClass().getInterfaces());
factory.setProxyTargetClass(false);
Target2 proxy = (Target2) factory.getProxy();
System.out.println(proxy.getClass());
proxy.foo();
proxy.bar();
/*
学到了什么
a. Spring 的代理选择规则
b. 底层的切点实现
c. 底层的通知实现
d. ProxyFactory 是用来创建代理的核心实现, 用 AopProxyFactory 选择具体代理实现
- JdkDynamicAopProxy
- ObjenesisCglibAopProxy
*/
}
interface I1 {
void foo();
void bar();
}
static class Target1 implements I1 {
public void foo() {
System.out.println("target1 foo");
}
public void bar() {
System.out.println("target1 bar");
}
}
static class Target2 {
public void foo() {
System.out.println("target2 foo");
}
public void bar() {
System.out.println("target2 bar");
}
}
}
2_切点匹配
切点匹配：
- 常见 aspectj 切点用法
- aspectj 切点的局限性，实际的 @Transactional 切点实现
import org.springframework.aop.aspectj.AspectJExpressionPointcut;
import org.springframework.aop.support.StaticMethodMatcherPointcut;
import org.springframework.core.annotation.MergedAnnotations;
import org.springframework.transaction.annotation.Transactional;
import java.lang.reflect.Method;
public class A16 {
public static void main(String[] args) throws NoSuchMethodException {
// AspectJExpressionPointcut pt1 = new AspectJExpressionPointcut();
// pt1.setExpression("execution(* bar())");
// System.out.println(pt1.matches(T1.class.getMethod("foo"), T1.class));
// System.out.println(pt1.matches(T1.class.getMethod("bar"), T1.class));
//
// AspectJExpressionPointcut pt2 = new AspectJExpressionPointcut();
// pt2.setExpression("@annotation(org.springframework.transaction.annotation.Transactional)");
// System.out.println(pt2.matches(T1.class.getMethod("foo"), T1.class));
// System.out.println(pt2.matches(T1.class.getMethod("bar"), T1.class));
StaticMethodMatcherPointcut pt3 = new StaticMethodMatcherPointcut() {
@Override
public boolean matches(Method method, Class<?> targetClass) {
// 检查方法上是否加了 Transactional 注解
MergedAnnotations annotations = MergedAnnotations.from(method);
if (annotations.isPresent(Transactional.class)) {
return true;
}
// 查看类上是否加了 Transactional 注解
annotations = MergedAnnotations.from(targetClass, MergedAnnotations.SearchStrategy.TYPE_HIERARCHY);
if (annotations.isPresent(Transactional.class)) {
return true;
}
return false;
}
};
System.out.println(pt3.matches(T1.class.getMethod("foo"), T1.class));
System.out.println(pt3.matches(T1.class.getMethod("bar"), T1.class));
System.out.println(pt3.matches(T2.class.getMethod("foo"), T2.class));
System.out.println(pt3.matches(T3.class.getMethod("foo"), T3.class));
/*
学到了什么
a. 底层切点实现是如何匹配的: 调用了 aspectj 的匹配方法
b. 比较关键的是它实现了 MethodMatcher 接口, 用来执行方法的匹配
*/
}
static class T1 {
@Transactional
public void foo() {
}
public void bar() {
}
}
@Transactional
static class T2 {
public void foo() {
}
}
@Transactional
interface I3 {
void foo();
}
static class T3 implements I3 {
public void foo() {
}
}
}
3_从 @Aspect 到 Advisor
1_代理创建器
注意点：
- AnnotationAwareAspectJAutoProxyCreator 的作用
- 将高级 @Aspect 切面统一为低级 Advisor 切面。
- 在合适的时机创建代理。
- findEligibleAdvisors 找到有【资格】的 Advisors
- 有【资格】的 Advisor 一部分是低级的, 可以由自己编写, 如本例 A17 中的 advisor3。
- 有【资格】的 Advisor 另一部分是高级的, 由解析 @Aspect 后获得。
wrapIfNecessary- 它内部调用
findEligibleAdvisors, 只要返回集合不空, 则表示需要创建代理。 - 它的调用时机通常在原始对象初始化后执行, 但碰到循环依赖会提前至依赖注入之前执行。
- 它内部调用
package org.springframework.aop.framework.autoproxy;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.aop.Advisor;
import org.springframework.aop.aspectj.AspectJExpressionPointcut;
import org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator;
import org.springframework.aop.support.DefaultPointcutAdvisor;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ConfigurationClassPostProcessor;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
/**
* @author shenyang
* @version 1.0
* @info TestAop
* @since 2024/8/17 20:26
*/
public class A17 {
@Aspect//高级切面
static class Aspect1{
@Before("execution(* foo())")
public void before(){
System.out.println("aspect1 before.....");
}
@After("execution(* foo())")
public void after(){
System.out.println("aspect1 after.....");
}
}
@Configuration
static class Config {
@Bean//低级切面
public Advisor advisor3(MethodInterceptor advice3) {
AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
pointcut.setExpression("execution(* foo())");
return new DefaultPointcutAdvisor(pointcut, advice3);
}
@Bean
public MethodInterceptor advice3(){
return new MethodInterceptor() {
@Override
public Object invoke(MethodInvocation methodInvocation) throws Throwable {
System.out.println("advice3 before.....");
Object proceed = methodInvocation.proceed();
System.out.println("advice3 after.....");
return proceed;
}
};
}
}
static class T1 {
public void foo() {
System.out.println("target1 foo");
}
}
static class T2 {
public void bar() {
System.out.println("target2 bar");
}
}
public static void main(String[] args) {
GenericApplicationContext context = new GenericApplicationContext();
context.registerBean("aspect1",Aspect1.class);
context.registerBean("config",Config.class);
context.registerBean(ConfigurationClassPostProcessor.class);
context.registerBean(AnnotationAwareAspectJAutoProxyCreator.class);
context.refresh();
AnnotationAwareAspectJAutoProxyCreator creator = context.getBean(AnnotationAwareAspectJAutoProxyCreator.class);
List<Advisor> advisors = creator.findEligibleAdvisors(T2.class, "target2");
System.out.println("====================");
// advisors.forEach(System.out::println);
T1 o1 = (T1) creator.wrapIfNecessary(new T1(), "target1", "target1");
T2 o2 = (T2) creator.wrapIfNecessary(new T2(), "target2", "target2");
System.out.println(o1.getClass()+" "+o2.getClass());
o1.foo();
o2.bar();
}
}
2_代理创建时机
注意点：
- 代理的创建时机
- 初始化之后 (无循环依赖时)
- 实例创建后, 依赖注入前 (有循环依赖时), 并暂存于二级缓存。
- 依赖注入与初始化不应该被增强, 仍应被施加于原始对象
package org.springframework.aop.framework.autoproxy;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.Advisor;
import org.springframework.aop.aspectj.AspectJExpressionPointcut;
import org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator;
import org.springframework.aop.support.DefaultPointcutAdvisor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.CommonAnnotationBeanPostProcessor;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ConfigurationClassPostProcessor;
import org.springframework.context.support.GenericApplicationContext;
import javax.annotation.PostConstruct;
public class A17_1 {
public static void main(String[] args) {
GenericApplicationContext context = new GenericApplicationContext();
context.registerBean(ConfigurationClassPostProcessor.class);
context.registerBean(Config.class);
context.refresh();
context.close();
// 创建 -> (*) 依赖注入 -> 初始化 (*)
/*
学到了什么
a. 代理的创建时机
1. 初始化之后 (无循环依赖时)
2. 实例创建后, 依赖注入前 (有循环依赖时), 并暂存于二级缓存
b. 依赖注入与初始化不应该被增强, 仍应被施加于原始对象
*/
}
@Configuration
static class Config {
@Bean // 解析 @Aspect、产生代理
public AnnotationAwareAspectJAutoProxyCreator annotationAwareAspectJAutoProxyCreator() {
return new AnnotationAwareAspectJAutoProxyCreator();
}
@Bean // 解析 @Autowired
public AutowiredAnnotationBeanPostProcessor autowiredAnnotationBeanPostProcessor() {
return new AutowiredAnnotationBeanPostProcessor();
}
@Bean // 解析 @PostConstruct
public CommonAnnotationBeanPostProcessor commonAnnotationBeanPostProcessor() {
return new CommonAnnotationBeanPostProcessor();
}
@Bean
public Advisor advisor(MethodInterceptor advice) {
AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
pointcut.setExpression("execution(* foo())");
return new DefaultPointcutAdvisor(pointcut, advice);
}
@Bean
public MethodInterceptor advice() {
return (MethodInvocation invocation) -> {
System.out.println("before...");
return invocation.proceed();
};
}
@Bean
public Bean1 bean1() {
return new Bean1();
}
@Bean
public Bean2 bean2() {
return new Bean2();
}
}
static class Bean1 {
public void foo() {
}
public Bean1() {
System.out.println("Bean1()");
}
@Autowired public void setBean2(Bean2 bean2) {
System.out.println("Bean1 setBean2(bean2) class is: " + bean2.getClass());
}
@PostConstruct public void init() {
System.out.println("Bean1 init()");
}
}
static class Bean2 {
public Bean2() {
System.out.println("Bean2()");
}
@Autowired public void setBean1(Bean1 bean1) {
System.out.println("Bean2 setBean1(bean1) class is: " + bean1.getClass());
}
@PostConstruct public void init() {
System.out.println("Bean2 init()");
}
}
}
3_@Before 对应的低级通知
注意点：
- @Before 前置通知会被转换为原始的 AspectJMethodBeforeAdvice 形式, 该对象包含了如下信息
- 通知代码从哪儿来
- 切点是什么(这里为啥要切点, 后面解释)
- 通知对象如何创建, 本例共用同一个 Aspect 对象
- 类似的还有
- AspectJAroundAdvice (环绕通知)
- AspectJAfterReturningAdvice
- AspectJAfterThrowingAdvice (环绕通知)
- AspectJAfterAdvice (环绕通知)
package org.springframework.aop.framework.autoproxy;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Before;
import org.springframework.aop.Advisor;
import org.springframework.aop.aspectj.AspectInstanceFactory;
import org.springframework.aop.aspectj.AspectJExpressionPointcut;
import org.springframework.aop.aspectj.AspectJMethodBeforeAdvice;
import org.springframework.aop.aspectj.SingletonAspectInstanceFactory;
import org.springframework.aop.support.DefaultPointcutAdvisor;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
public class A17_2 {
static class Aspect {
@Before("execution(* foo())")
public void before1() {
System.out.println("before1");
}
@Before("execution(* foo())")
public void before2() {
System.out.println("before2");
}
public void after() {
System.out.println("after");
}
public void afterReturning() {
System.out.println("afterReturning");
}
public void afterThrowing() {
System.out.println("afterThrowing");
}
public Object around(ProceedingJoinPoint pjp) throws Throwable {
try {
System.out.println("around...before");
return pjp.proceed();
} finally {
System.out.println("around...after");
}
}
}
static class Target {
public void foo() {
System.out.println("target foo");
}
}
@SuppressWarnings("all")
public static void main(String[] args) throws Throwable {
AspectInstanceFactory factory = new SingletonAspectInstanceFactory(new Aspect());
// 高级切面转低级切面类
List<Advisor> list = new ArrayList<>();
for (Method method : Aspect.class.getDeclaredMethods()) {
if (method.isAnnotationPresent(Before.class)) {
// 解析切点
String expression = method.getAnnotation(Before.class).value();
AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
pointcut.setExpression(expression);
// 通知类
AspectJMethodBeforeAdvice advice = new AspectJMethodBeforeAdvice(method, pointcut, factory);
// 切面
Advisor advisor = new DefaultPointcutAdvisor(pointcut, advice);
list.add(advisor);
}
}
for (Advisor advisor : list) {
System.out.println(advisor);
}
/*
@Before 前置通知会被转换为下面原始的 AspectJMethodBeforeAdvice 形式, 该对象包含了如下信息
a. 通知代码从哪儿来
b. 切点是什么(这里为啥要切点, 后面解释)
c. 通知对象如何创建, 本例共用同一个 Aspect 对象
类似的通知还有
1. AspectJAroundAdvice (环绕通知)
2. AspectJAfterReturningAdvice
3. AspectJAfterThrowingAdvice
4. AspectJAfterAdvice (环绕通知)
*/
}
}
4_静态通知调用
代理对象调用流程如下（以 JDK 动态代理实现为例）
- 从 ProxyFactory 获得 Target 和环绕通知链，根据他俩创建 MethodInvocation，简称 mi
- 首次执行 mi.proceed() 发现有下一个环绕通知，调用它的 invoke(mi)
- 进入环绕通知1，执行前增强，再次调用 mi.proceed() 发现有下一个环绕通知，调用它的 invoke(mi)
- 进入环绕通知2，执行前增强，调用 mi.proceed() 发现没有环绕通知，调用 mi.invokeJoinPoint() 执行目标方法
- 目标方法执行结束，将结果返回给环绕通知2，执行环绕通知2 的后增强
- 环绕通知2继续将结果返回给环绕通知1，执行环绕通知1 的后增强
- 环绕通知1返回最终的结果
图中不同颜色对应一次环绕通知或目标的调用起始至终结
1_通知调用过程
代理方法执行时会做如下工作：
- 通过 proxyFactory 的 getInterceptorsAndDynamicInterceptionAdvice() 将其他通知统一转换为 MethodInterceptor 环绕通知
- MethodBeforeAdviceAdapter 将 @Before AspectJMethodBeforeAdvice 适配为 MethodBeforeAdviceInterceptor
- AfterReturningAdviceAdapter 将 @AfterReturning AspectJAfterReturningAdvice 适配为 AfterReturningAdviceInterceptor
- 这体现的是适配器设计模式
- 所谓静态通知，体现在上面方法的 Interceptors 部分，这些通知调用时无需再次检查切点，直接调用即可
- 结合目标与环绕通知链，创建 MethodInvocation 对象，通过它完成整个调用
package org.springframework.aop.framework;
import org.aopalliance.intercept.MethodInvocation;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Before;
import org.springframework.aop.Advisor;
import org.springframework.aop.aspectj.*;
import org.springframework.aop.framework.ProxyFactory;
import org.springframework.aop.framework.ReflectiveMethodInvocation;
import org.springframework.aop.interceptor.ExposeInvocationInterceptor;
import org.springframework.aop.support.DefaultPointcutAdvisor;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
public class A18 {
static class Aspect {
@Before("execution(* foo())")
public void before1() {
System.out.println("before1");
}
@Before("execution(* foo())")
public void before2() {
System.out.println("before2");
}
public void after() {
System.out.println("after");
}
@AfterReturning("execution(* foo())")
public void afterReturning() {
System.out.println("afterReturning");
}
@AfterThrowing("execution(* foo())")
public void afterThrowing(Exception e) {
System.out.println("afterThrowing " + e.getMessage());
}
@Around("execution(* foo())")
public Object around(ProceedingJoinPoint pjp) throws Throwable {
try {
System.out.println("around...before");
return pjp.proceed();
} finally {
System.out.println("around...after");
}
}
}
static class Target {
public void foo() {
System.out.println("target foo");
}
}
@SuppressWarnings("all")
public static void main(String[] args) throws Throwable {
AspectInstanceFactory factory = new SingletonAspectInstanceFactory(new Aspect());
// 1. 高级切面转低级切面类
List<Advisor> list = new ArrayList<>();
for (Method method : Aspect.class.getDeclaredMethods()) {
if (method.isAnnotationPresent(Before.class)) {
// 解析切点
String expression = method.getAnnotation(Before.class).value();
AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
pointcut.setExpression(expression);
// 通知类
AspectJMethodBeforeAdvice advice = new AspectJMethodBeforeAdvice(method, pointcut, factory);
// 切面
Advisor advisor = new DefaultPointcutAdvisor(pointcut, advice);
list.add(advisor);
} else if (method.isAnnotationPresent(AfterReturning.class)) {
// 解析切点
String expression = method.getAnnotation(AfterReturning.class).value();
AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
pointcut.setExpression(expression);
// 通知类
AspectJAfterReturningAdvice advice = new AspectJAfterReturningAdvice(method, pointcut, factory);
// 切面
Advisor advisor = new DefaultPointcutAdvisor(pointcut, advice);
list.add(advisor);
} else if (method.isAnnotationPresent(Around.class)) {
// 解析切点
String expression = method.getAnnotation(Around.class).value();
AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
pointcut.setExpression(expression);
// 通知类
AspectJAroundAdvice advice = new AspectJAroundAdvice(method, pointcut, factory);
// 切面
Advisor advisor = new DefaultPointcutAdvisor(pointcut, advice);
list.add(advisor);
}
}
for (Advisor advisor : list) {
System.out.println(advisor);
}
/*
@Before 前置通知会被转换为下面原始的 AspectJMethodBeforeAdvice 形式, 该对象包含了如下信息
a. 通知代码从哪儿来
b. 切点是什么
c. 通知对象如何创建, 本例共用同一个 Aspect 对象
类似的通知还有
1. AspectJAroundAdvice (环绕通知)
2. AspectJAfterReturningAdvice
3. AspectJAfterThrowingAdvice (环绕通知)
4. AspectJAfterAdvice (环绕通知)
*/
// 2. 通知统一转换为环绕通知 MethodInterceptor
/*
其实无论 ProxyFactory 基于哪种方式创建代理, 最后干活(调用 advice)的是一个 MethodInvocation 对象
a. 因为 advisor 有多个, 且一个套一个调用, 因此需要一个调用链对象, 即 MethodInvocation
b. MethodInvocation 要知道 advice 有哪些, 还要知道目标, 调用次序如下
将 MethodInvocation 放入当前线程
|-> before1 ----------------------------------- 从当前线程获取 MethodInvocation
| |
| |-> before2 -------------------- | 从当前线程获取 MethodInvocation
| | | |
| | |-> target ------ 目标 advice2 advice1
| | | |
| |-> after2 --------------------- |
| |
|-> after1 ------------------------------------
c. 从上图看出, 环绕通知才适合作为 advice, 因此其他 before、afterReturning 都会被转换成环绕通知
d. 统一转换为环绕通知, 体现的是设计模式中的适配器模式
- 对外是为了方便使用要区分 before、afterReturning
- 对内统一都是环绕通知, 统一用 MethodInterceptor 表示
此步获取所有执行时需要的 advice (静态)
a. 即统一转换为 MethodInterceptor 环绕通知, 这体现在方法名中的 Interceptors 上
b. 适配如下
- MethodBeforeAdviceAdapter 将 @Before AspectJMethodBeforeAdvice 适配为 MethodBeforeAdviceInterceptor
- AfterReturningAdviceAdapter 将 @AfterReturning AspectJAfterReturningAdvice 适配为 AfterReturningAdviceInterceptor
*/
Target target = new Target();
ProxyFactory proxyFactory = new ProxyFactory();
proxyFactory.setTarget(target);
proxyFactory.addAdvice(ExposeInvocationInterceptor.INSTANCE); // 准备把 MethodInvocation 放入当前线程
proxyFactory.addAdvisors(list);
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>");
List<Object> methodInterceptorList = proxyFactory.getInterceptorsAndDynamicInterceptionAdvice(Target.class.getMethod("foo"), Target.class);
for (Object o : methodInterceptorList) {
System.out.println(o);
}
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>");
// 3. 创建并执行调用链 (环绕通知s + 目标)
MethodInvocation methodInvocation = new ReflectiveMethodInvocation(
null, target, Target.class.getMethod("foo"), new Object[0], Target.class, methodInterceptorList
);
methodInvocation.proceed();
/*
学到了什么
a. 无参数绑定的通知如何被调用
b. MethodInvocation 编程技巧: 拦截器、过滤器等等实现都与此类似
c. 适配器模式在 Spring 中的体现
*/
}
}
2_模拟 MethodInvocation
注意点：
- proceed() 方法调用链中下一个环绕通知
- 每个环绕通知内部继续调用 proceed()
- 调用到没有更多通知了, 就调用目标方法
MethodInvocation 的编程技巧在实现拦截器、过滤器时能用上
package org.springframework.aop.framework;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
/*
模拟调用链过程, 是一个简单的递归过程
1. proceed() 方法调用链中下一个环绕通知
2. 每个环绕通知内部继续调用 proceed()
3. 调用到没有更多通知了, 就调用目标方法
*/
public class A18_1 {
static class Target {
public void foo() {
System.out.println("Target.foo()");
}
}
static class Advice1 implements MethodInterceptor {
public Object invoke(MethodInvocation invocation) throws Throwable {
System.out.println("Advice1.before()");
Object result = invocation.proceed();// 调用下一个通知或目标
System.out.println("Advice1.after()");
return result;
}
}
static class Advice2 implements MethodInterceptor {
public Object invoke(MethodInvocation invocation) throws Throwable {
System.out.println("Advice2.before()");
Object result = invocation.proceed();// 调用下一个通知或目标
System.out.println("Advice2.after()");
return result;
}
}
static class MyInvocation implements MethodInvocation {
private Object target; // 1
private Method method;
private Object[] args;
List<MethodInterceptor> methodInterceptorList; // 2
private int count = 1; // 调用次数
public MyInvocation(Object target, Method method, Object[] args, List<MethodInterceptor> methodInterceptorList) {
this.target = target;
this.method = method;
this.args = args;
this.methodInterceptorList = methodInterceptorList;
}
@Override
public Method getMethod() {
return method;
}
@Override
public Object[] getArguments() {
return args;
}
@Override
public Object proceed() throws Throwable { // 调用每一个环绕通知, 调用目标
if (count > methodInterceptorList.size()) {
// 调用目标， 返回并结束递归
return method.invoke(target, args);
}
// 逐一调用通知, count + 1
MethodInterceptor methodInterceptor = methodInterceptorList.get(count++ - 1);
return methodInterceptor.invoke(this);
}
@Override
public Object getThis() {
return target;
}
@Override
public AccessibleObject getStaticPart() {
return method;
}
}
public static void main(String[] args) throws Throwable {
Target target = new Target();
List<MethodInterceptor> list = new ArrayList<>();
list.add(new Advice1());
list.add(new Advice2());
MyInvocation invocation = new MyInvocation(target, Target.class.getMethod("foo"), new Object[0], list);
invocation.proceed();
}
}
5_动态通知调用
注意点：
- 通过 proxyFactory 的 getInterceptorsAndDynamicInterceptionAdvice() 将其他通知统一转换为 MethodInterceptor 环绕通知
- 所谓动态通知，体现在上面方法的 DynamicInterceptionAdvice 部分，这些通知调用时因为要为通知方法绑定参数，还需再次利用切点表达式
- 动态通知调用复杂程度高，性能较低
package org.springframework.aop.framework.autoproxy;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.aop.Advisor;
import org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator;
import org.springframework.aop.framework.ProxyFactory;
import org.springframework.aop.framework.ReflectiveMethodInvocation;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ConfigurationClassPostProcessor;
import org.springframework.context.support.GenericApplicationContext;
import java.lang.reflect.Field;
import java.util.List;
public class A19 {
@Aspect
static class MyAspect {
@Before("execution(* foo(..))") // 静态通知调用，不带参数绑定，执行时不需要切点
public void before1() {
System.out.println("before1");
}
@Before("execution(* foo(..)) && args(x)") // 动态通知调用，需要参数绑定，执行时还需要切点对象
public void before2(int x) {
System.out.printf("before2(%d)%n", x);
}
}
static class Target {
public void foo(int x) {
System.out.printf("target foo(%d)%n", x);
}
}
@Configuration
static class MyConfig {
@Bean
AnnotationAwareAspectJAutoProxyCreator proxyCreator() {
return new AnnotationAwareAspectJAutoProxyCreator();
}
@Bean
public MyAspect myAspect() {
return new MyAspect();
}
}
public static void main(String[] args) throws Throwable {
GenericApplicationContext context = new GenericApplicationContext();
context.registerBean(ConfigurationClassPostProcessor.class);
context.registerBean(MyConfig.class);
context.refresh();
AnnotationAwareAspectJAutoProxyCreator creator = context.getBean(AnnotationAwareAspectJAutoProxyCreator.class);
List<Advisor> list = creator.findEligibleAdvisors(Target.class, "target");
Target target = new Target();
ProxyFactory factory = new ProxyFactory();
factory.setTarget(target);
factory.addAdvisors(list);
Object proxy = factory.getProxy(); // 获取代理
List<Object> interceptorList = factory.getInterceptorsAndDynamicInterceptionAdvice(Target.class.getMethod("foo", int.class), Target.class);
for (Object o : interceptorList) {
showDetail(o);
}
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>");
ReflectiveMethodInvocation invocation = new ReflectiveMethodInvocation(
proxy, target, Target.class.getMethod("foo", int.class), new Object[]{100}, Target.class, interceptorList
) {};
invocation.proceed();
/*
学到了什么
a. 有参数绑定的通知调用时还需要切点，对参数进行匹配及绑定
b. 复杂程度高, 性能比无参数绑定的通知调用低
*/
}
public static void showDetail(Object o) {
try {
Class<?> clazz = Class.forName("org.springframework.aop.framework.InterceptorAndDynamicMethodMatcher");
if (clazz.isInstance(o)) {
Field methodMatcher = clazz.getDeclaredField("methodMatcher");
methodMatcher.setAccessible(true);
Field methodInterceptor = clazz.getDeclaredField("interceptor");
methodInterceptor.setAccessible(true);
System.out.println("环绕通知和切点：" + o);
System.out.println("\t切点为：" + methodMatcher.get(o));
System.out.println("\t通知为：" + methodInterceptor.get(o));
} else {
System.out.println("普通环绕通知：" + o);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
补充—— Advice 常见子接口：
| 增强类型 | 常见 Advice 子接口/子类 | 描述 |
|---|---|---|
| 前置通知 | MethodBeforeAdvice | 方法调用前执行 |
| 后置通知 | AfterReturningAdvice | 方法调用后且正常返回时执行 |
| 环绕通知 | MethodInterceptor | 方法调用前后都可增强，控制流程 |
| 异常通知 | ThrowsAdvice | 方法抛出异常时增强 |
| 引介通知 | DelegatingIntroductionInterceptor | 为目标对象动态添加接口实现 |
