AOP 底层实现方式之一是代理,由代理结合通知和目标,提供增强功能
除此以外,aspectj 提供了两种另外的 AOP 底层实现:
第一种是通过 ajc 编译器在编译 class 类文件时,就把通知的增强功能,织入到目标类的字节码中
第二种是通过 agent 在加载目标类时,修改目标类的字节码,织入增强功能
作为对比,之前学习的代理是运行时生成新的字节码
简单比较的话:
代码参考
package com.itheima;
import com.itheima.service.MyService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/*
注意几点
1. 版本选择了 java 8, 因为目前的 aspectj-maven-plugin 1.14.0 最高只支持到 java 16
2. 一定要用 maven 的 compile 来编译, idea 不会调用 ajc 编译器
*/
@SpringBootApplication
public class A09 {
private static final Logger log = LoggerFactory.getLogger(A09.class);
public static void main(String[] args) {
// ConfigurableApplicationContext context = SpringApplication.run(A10Application.class, args);
// MyService service = context.getBean(MyService.class);
//
// log.debug("service class: {}", service.getClass());
// service.foo();
//
// context.close();
new MyService().foo();
/*
学到了什么
1. aop 的原理并非代理一种, 编译器也能玩出花样
*/
}
}
package com.itheima.aop;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@Aspect // ⬅️注意此切面并未被 Spring 管理
public class MyAspect {
private static final Logger log = LoggerFactory.getLogger(MyAspect.class);
@Before("execution(* com.itheima.service.MyService.foo())")
public void before() {
log.debug("before()");
}
}
package com.itheima.service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
@Service
public class MyService {
private static final Logger log = LoggerFactory.getLogger(MyService.class);
public static void foo() {
log.debug("foo()");
}
}
<dependencies>
..........
<dependency>
<groupId>org.aspectjgroupId>
<artifactId>aspectjweaverartifactId>
dependency>
<dependency>
<groupId>org.aspectjgroupId>
<artifactId>aspectjrtartifactId>
dependency>
dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-maven-pluginartifactId>
plugin>
<plugin>
<groupId>org.codehaus.mojogroupId>
<artifactId>aspectj-maven-pluginartifactId>
<version>1.14.0version>
<configuration>
<complianceLevel>1.8complianceLevel>
<source>8source>
<target>8target>
<showWeaveInfo>trueshowWeaveInfo>
<verbose>trueverbose>
<Xlint>ignoreXlint>
<encoding>UTF-8encoding>
configuration>
<executions>
<execution>
<goals>
<goal>compilegoal>
<goal>test-compilegoal>
goals>
execution>
executions>
plugin>
plugins>
build>
注意
- 版本选择了 java 8, 因为目前的 aspectj-maven-plugin 1.14.0 最高只支持到 java 16
- 一定要用 maven 的 compile 来编译, idea 不会调用 ajc 编译器
代码参考
package com.itheima;
import com.itheima.service.MyService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
/*
注意几点
1. 版本选择了 java 8, 因为目前的 aspectj-maven-plugin 1.14.0 最高只支持到 java 16
2. 运行时需要在 VM options 里加入 -javaagent:C:/Users/manyh/.m2/repository/org/aspectj/aspectjweaver/1.9.7/aspectjweaver-1.9.7.jar
把其中 C:/Users/manyh/.m2/repository 改为你自己 maven 仓库起始地址
*/
@SpringBootApplication
public class A10 {
private static final Logger log = LoggerFactory.getLogger(A10.class);
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(A10.class, args);
MyService service = context.getBean(MyService.class);
// ⬇️MyService 并非代理, 但 foo 方法也被增强了, 做增强的 java agent, 在加载类时, 修改了 class 字节码
log.debug("service class: {}", service.getClass());
service.foo();
// context.close();
/*
学到了什么
1. aop 的原理并非代理一种, agent 也能, 只要字节码变了, 行为就变了
*/
}
}
public class JdkProxyDemo {
interface Foo {
void foo();
}
static class Target implements Foo {
public void foo() {
System.out.println("target foo");
}
}
public static void main(String[] param) {
// 目标对象
Target target = new Target();
// 代理对象
Foo proxy = (Foo) Proxy.newProxyInstance(
Target.class.getClassLoader(), new Class[]{Foo.class},
(p, method, args) -> {
System.out.println("proxy before...");
Object result = method.invoke(target, args);
System.out.println("proxy after...");
return result;
});
// 调用代理
proxy.foo();
}
}
运行结果
proxy before...
target foo
proxy after...
public class CglibProxyDemo {
static class Target {
public void foo() {
System.out.println("target foo");
}
}
public static void main(String[] param) {
// 目标对象
Target target = new Target();
// 代理对象
Target proxy = (Target) Enhancer.create(Target.class,
(MethodInterceptor) (p, method, args, methodProxy) -> {
System.out.println("proxy before...");
Object result = methodProxy.invoke(target, args);
// 另一种调用方法,不需要目标对象实例
// Object result = methodProxy.invokeSuper(p, args);
System.out.println("proxy after...");
return result;
});
// 调用代理
proxy.foo();
}
}
运行结果与 jdk 动态代理相同
public class A12 {
interface Foo {
void foo();
int bar();
}
static class Target implements Foo {
public void foo() {
System.out.println("target foo");
}
public int bar() {
System.out.println("target bar");
return 100;
}
}
public static void main(String[] param) {
// ⬇️1. 创建代理,这时传入 InvocationHandler
Foo proxy = new $Proxy0(new InvocationHandler() {
// ⬇️5. 进入 InvocationHandler
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable{
// ⬇️6. 功能增强
System.out.println("before...");
// ⬇️7. 反射调用目标方法
return method.invoke(new Target(), args);
}
});
// ⬇️2. 调用代理方法
proxy.foo();
proxy.bar();
}
}
模拟代理实现
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
// ⬇️这就是 jdk 代理类的源码, 秘密都在里面
public class $Proxy0 extends Proxy implements A12.Foo {
public $Proxy0(InvocationHandler h) {
super(h);
}
// ⬇️3. 进入代理方法
public void foo() {
try {
// ⬇️4. 回调 InvocationHandler
h.invoke(this, foo, new Object[0]);
} catch (RuntimeException | Error e) {
throw e;
} catch (Throwable e) {
throw new UndeclaredThrowableException(e);
}
}
@Override
public int bar() {
try {
Object result = h.invoke(this, bar, new Object[0]);
return (int) result;
} catch (RuntimeException | Error e) {
throw e;
} catch (Throwable e) {
throw new UndeclaredThrowableException(e);
}
}
static Method foo;
static Method bar;
static {
try {
foo = A12.Foo.class.getMethod("foo");
bar = A12.Foo.class.getMethod("bar");
} catch (NoSuchMethodException e) {
throw new NoSuchMethodError(e.getMessage());
}
}
}
代理一点都不难,无非就是利用了多态、反射的知识
package com.itheima.a12;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
// 运行时请添加 --add-opens java.base/java.lang.reflect=ALL-UNNAMED --add-opens java.base/jdk.internal.reflect=ALL-UNNAMED
public class TestMethodInvoke {
public static void main(String[] args) throws Exception {
Method foo = TestMethodInvoke.class.getMethod("foo", int.class);
for (int i = 1; i <= 17; i++) {
show(i, foo);
foo.invoke(null, i);
}
System.in.read();
}
// 方法反射调用时, 底层 MethodAccessor 的实现类
private static void show(int i, Method foo) throws Exception {
Method getMethodAccessor = Method.class.getDeclaredMethod("getMethodAccessor");
getMethodAccessor.setAccessible(true);
Object invoke = getMethodAccessor.invoke(foo);
if (invoke == null) {
System.out.println(i + ":" + null);
return;
}
Field delegate = Class.forName("jdk.internal.reflect.DelegatingMethodAccessorImpl").getDeclaredField("delegate");
delegate.setAccessible(true);
System.out.println(i + ":" + delegate.get(invoke));
}
public static void foo(int i) {
System.out.println(i + ":" + "foo");
}
}
注意
运行时请添加 --add-opens java.base/java.lang.reflect=ALL-UNNAMED --add-opens java.base/jdk.internal.reflect=ALL-UNNAMED
package com.itheima.a13;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
public class A13 {
public static void main(String[] args) {
Proxy proxy = new Proxy();
Target target = new Target();
proxy.setMethodInterceptor(new MethodInterceptor() {
@Override
public Object intercept(Object p, Method method, Object[] args,
MethodProxy methodProxy) throws Throwable {
System.out.println("before...");
// return method.invoke(target, args); // 反射调用
// FastClass
// return methodProxy.invoke(target, args); // 内部无反射, 结合目标用
return methodProxy.invokeSuper(p, args); // 内部无反射, 结合代理用
}
});
proxy.save();
proxy.save(1);
proxy.save(2L);
}
}
package com.itheima.a13;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
import java.lang.reflect.UndeclaredThrowableException;
public class Proxy extends Target {
private MethodInterceptor methodInterceptor;
public void setMethodInterceptor(MethodInterceptor methodInterceptor) {
this.methodInterceptor = methodInterceptor;
}
static Method save0;
static Method save1;
static Method save2;
static MethodProxy save0Proxy;
static MethodProxy save1Proxy;
static MethodProxy save2Proxy;
static {
try {
save0 = Target.class.getMethod("save");
save1 = Target.class.getMethod("save", int.class);
save2 = Target.class.getMethod("save", long.class);
save0Proxy = MethodProxy.create(Target.class, Proxy.class, "()V", "save", "saveSuper");
save1Proxy = MethodProxy.create(Target.class, Proxy.class, "(I)V", "save", "saveSuper");
save2Proxy = MethodProxy.create(Target.class, Proxy.class, "(J)V", "save", "saveSuper");
} catch (NoSuchMethodException e) {
throw new NoSuchMethodError(e.getMessage());
}
}
// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 带原始功能的方法
public void saveSuper() {
super.save();
}
public void saveSuper(int i) {
super.save(i);
}
public void saveSuper(long j) {
super.save(j);
}
// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 带增强功能的方法
@Override
public void save() {
try {
methodInterceptor.intercept(this, save0, new Object[0], save0Proxy);
} catch (Throwable e) {
throw new UndeclaredThrowableException(e);
}
}
@Override
public void save(int i) {
try {
methodInterceptor.intercept(this, save1, new Object[]{i}, save1Proxy);
} catch (Throwable e) {
throw new UndeclaredThrowableException(e);
}
}
@Override
public void save(long j) {
try {
methodInterceptor.intercept(this, save2, new Object[]{j}, save2Proxy);
} catch (Throwable e) {
throw new UndeclaredThrowableException(e);
}
}
}
package com.itheima.a13;
public class Target {
public void save() {
System.out.println("save()");
}
public void save(int i) {
System.out.println("save(int)");
}
public void save(long j) {
System.out.println("save(long)");
}
}
和 jdk 动态代理原理查不多
public class A14Application {
public static void main(String[] args) throws InvocationTargetException {
Target target = new Target();
Proxy proxy = new Proxy();
proxy.setCallbacks(new Callback[]{(MethodInterceptor) (p, m, a, mp) -> {
System.out.println("proxy before..." + mp.getSignature());
// ⬇️调用目标方法(三种)
// Object result = m.invoke(target, a); // ⬅️反射调用
// Object result = mp.invoke(target, a); // ⬅️非反射调用, 结合目标用
Object result = mp.invokeSuper(p, a); // ⬅️非反射调用, 结合代理用
System.out.println("proxy after..." + mp.getSignature());
return result;
}});
// ⬇️调用代理方法
proxy.save();
}
}
注意
- 调用 Object 的方法, 后两种在 jdk >= 9 时都有问题, 需要 --add-opens java.base/java.lang=ALL-UNNAMED
package com.itheima.a13;
import org.springframework.cglib.core.Signature;
public class TargetFastClass {
static Signature s0 = new Signature("save", "()V");
static Signature s1 = new Signature("save", "(I)V");
static Signature s2 = new Signature("save", "(J)V");
// 获取目标方法的编号
/*
Target
save() 0
save(int) 1
save(long) 2
signature 包括方法名字、参数返回值
*/
public int getIndex(Signature signature) {
if (s0.equals(signature)) {
return 0;
} else if (s1.equals(signature)) {
return 1;
} else if (s2.equals(signature)) {
return 2;
}
return -1;
}
// 根据方法编号, 正常调用目标对象方法
public Object invoke(int index, Object target, Object[] args) {
if (index == 0) {
((Target) target).save();
return null;
} else if (index == 1) {
((Target) target).save((int) args[0]);
return null;
} else if (index == 2) {
((Target) target).save((long) args[0]);
return null;
} else {
throw new RuntimeException("无此方法");
}
}
public static void main(String[] args) {
TargetFastClass fastClass = new TargetFastClass();
int index = fastClass.getIndex(new Signature("save", "(I)V"));
System.out.println(index);
fastClass.invoke(index, new Target(), new Object[]{100});
}
}
package com.itheima.a13;
import org.springframework.cglib.core.Signature;
public class ProxyFastClass {
static Signature s0 = new Signature("saveSuper", "()V");
static Signature s1 = new Signature("saveSuper", "(I)V");
static Signature s2 = new Signature("saveSuper", "(J)V");
// 获取代理方法的编号
/*
Proxy
saveSuper() 0
saveSuper(int) 1
saveSuper(long) 2
signature 包括方法名字、参数返回值
*/
public int getIndex(Signature signature) {
if (s0.equals(signature)) {
return 0;
} else if (s1.equals(signature)) {
return 1;
} else if (s2.equals(signature)) {
return 2;
}
return -1;
}
// 根据方法编号, 正常调用目标对象方法
public Object invoke(int index, Object proxy, Object[] args) {
if (index == 0) {
((Proxy) proxy).saveSuper();
return null;
} else if (index == 1) {
((Proxy) proxy).saveSuper((int) args[0]);
return null;
} else if (index == 2) {
((Proxy) proxy).saveSuper((long) args[0]);
return null;
} else {
throw new RuntimeException("无此方法");
}
}
public static void main(String[] args) {
ProxyFastClass fastClass = new ProxyFastClass();
int index = fastClass.getIndex(new Signature("saveSuper", "()V"));
System.out.println(index);
fastClass.invoke(index, new Proxy(), new Object[0]);
}
}
Spring 中对切点、通知、切面的抽象如下
代理相关类图
package com.itheima.a15;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.aspectj.AspectJExpressionPointcut;
import org.springframework.aop.framework.ProxyFactory;
import org.springframework.aop.support.DefaultPointcutAdvisor;
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");
}
}
}
注意
- 要区分本章节提到的 MethodInterceptor,它与之前 cglib 中用的的 MethodInterceptor 是不同的接口
package com.itheima.a16;
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() {
}
}
}
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.context.annotation.Configuration;
import org.springframework.context.annotation.ConfigurationClassPostProcessor;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.annotation.Order;
import java.util.List;
public class A17 {
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);
// BeanPostProcessor
// 创建 -> (*) 依赖注入 -> 初始化 (*)
context.refresh();
// for (String name : context.getBeanDefinitionNames()) {
// System.out.println(name);
// }
/*
第一个重要方法 findEligibleAdvisors 找到有【资格】的 Advisors
a. 有【资格】的 Advisor 一部分是低级的, 可以由自己编写, 如下例中的 advisor3
b. 有【资格】的 Advisor 另一部分是高级的, 由本章的主角解析 @Aspect 后获得
*/
AnnotationAwareAspectJAutoProxyCreator creator = context.getBean(AnnotationAwareAspectJAutoProxyCreator.class);
List<Advisor> advisors = creator.findEligibleAdvisors(Target2.class, "target2");
/*for (Advisor advisor : advisors) {
System.out.println(advisor);
}*/
/*
第二个重要方法 wrapIfNecessary
a. 它内部调用 findEligibleAdvisors, 只要返回集合不空, 则表示需要创建代理
*/
Object o1 = creator.wrapIfNecessary(new Target1(), "target1", "target1");
System.out.println(o1.getClass());
Object o2 = creator.wrapIfNecessary(new Target2(), "target2", "target2");
System.out.println(o2.getClass());
((Target1) o1).foo();
/*
学到了什么
a. 自动代理后处理器 AnnotationAwareAspectJAutoProxyCreator 会帮我们创建代理
b. 通常代理创建的活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
c. 高级的 @Aspect 切面会转换为低级的 Advisor 切面, 理解原理, 大道至简
*/
}
static class Target1 {
public void foo() {
System.out.println("target1 foo");
}
}
static class Target2 {
public void bar() {
System.out.println("target2 bar");
}
}
@Aspect // 高级切面类
@Order(1)
static class Aspect1 {
@Before("execution(* foo())")
public void before1() {
System.out.println("aspect1 before1...");
}
@Before("execution(* foo())")
public void before2() {
System.out.println("aspect1 before2...");
}
}
@Configuration
static class Config {
/*@Bean // 低级切面
public Advisor advisor3(MethodInterceptor advice3) {
AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
pointcut.setExpression("execution(* foo())");
DefaultPointcutAdvisor advisor = new DefaultPointcutAdvisor(pointcut, advice3);
return advisor;
}
@Bean
public MethodInterceptor advice3() {
return invocation -> {
System.out.println("advice3 before...");
Object result = invocation.proceed();
System.out.println("advice3 after...");
return result;
};
}*/
}
}
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()");
}
}
}
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.interceptor.ExposeInvocationInterceptor;
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)
*/
}
}
代理对象调用流程如下(以 JDK 动态代理实现为例)
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
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.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
*/
}
}
代理方法执行时会做如下工作
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.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 = List.of(
new Advice1(),
new Advice2()
);
MyInvocation invocation = new MyInvocation(target, Target.class.getMethod("foo"), new Object[0], list);
invocation.proceed();
}
}
MethodInvocation 的编程技巧在实现拦截器、过滤器时能用上
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();
}
}
}