Spring从@Aspect到Advisor使用演示实例

Spring @Aspect Advisor Spring @Aspect Spring Advisor 2023-02-08 09:02:35 468人浏览独家记忆

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摘要

演示1 - 代理创建器 public class A17 { public static void main(String[] args) { Generic

演示1 - 代理创建器

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);
//        }
        
        AnnotationAwareAspectJAutoProxyCreator creator = context.getBean(AnnotationAwareAspectJAutoProxyCreator.class);
        List<Advisor> advisors = creator.findEligibleAdvisors(Target2.class, "target2");
        
        
        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();
        
    }
    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 {
        
    }
}

收获?

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

演示2 - 代理创建时机

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 (*)
        
    }
    @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()");
        }
    }
}

收获?

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

演示3 - @Before 对应的低级通知

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);
        }
        
    }
}

收获?

@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