Question

是否可以捕获具有特定注释的任何字段？我的最终目标是在该字段中注入一个值，但目前我的切入点是错误的（不确定正确的语法）。

@Pointcut("execution(* *(..)) && @annotation(com.mycompany.MyAnnotation)")
private void annotatedField(){}

@Around("annotatedField()")
public Object injectValue(final ProceedingJoinPoint proceedingJoinPoint) throws Throwable {}

我相信切入点会说明任何带注释的方法。我想改变它来说任何Field。

Answer 1

我认为你应该遵循 Sotirios Delimanolis 的建议，尽可能使用Spring on-board方式。如果那时你仍然认为它们不够并且绝对想要使用方面来实现你的想法，你可以使用AspectJ within Spring而不是Spring AOP，并利用get()和set()等切入点的全部功能为了拦截类成员（静态和非静态）的读/写操作。例如：

标记注释：

package de.scrum_master.app;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface MyAnnotation {}

驱动程序应用程序：

应用程序读取（toString()）并写入（构造函数，main方法）所有字段，其中包括带注释的status字段。

package de.scrum_master.app;

public class Application {
    private int id;
    private String name;
    @MyAnnotation private String status;

    public Application(int id, String name, String status) {
        this.id = id;
        this.name = name;
        this.status = status;
    }

    @Override
    public String toString() {
        return "Application [id=" + id + ", name=" + name + ", status=" + status + "]";
    }

    public static void main(String[] args) {
        Application application = new Application(11, "AspectJ demo", "starting");
        System.out.println(application);
        application.id = 22;
        application.name = "AspectJ field access demo";
        application.status = "running";
        System.out.println(application);
        application.status = "shutting down";
        System.out.println(application);
        application.status = "stopped";
        System.out.println(application);
    }
}

<强>方面：

package de.scrum_master.aspect;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

@Aspect
public class AnnotatedFieldAspect {
    @Before("get(* *) && @annotation(de.scrum_master.app.MyAnnotation)")
    public void interceptRead(JoinPoint thisJoinPoint) {
        System.out.println(thisJoinPoint);
    }

    @Before("set(* *) && @annotation(de.scrum_master.app.MyAnnotation) && args(newValue)")
    public void interceptWrite(JoinPoint thisJoinPoint, Object newValue) {
        System.out.println(thisJoinPoint + " -> " + newValue);
    }
}

控制台日志：

set(String de.scrum_master.app.Application.status) -> starting
get(String de.scrum_master.app.Application.status)
Application [id=11, name=AspectJ demo, status=starting]
set(String de.scrum_master.app.Application.status) -> running
get(String de.scrum_master.app.Application.status)
Application [id=22, name=AspectJ field access demo, status=running]
set(String de.scrum_master.app.Application.status) -> shutting down
get(String de.scrum_master.app.Application.status)
Application [id=22, name=AspectJ field access demo, status=shutting down]
set(String de.scrum_master.app.Application.status) -> stopped
get(String de.scrum_master.app.Application.status)
Application [id=22, name=AspectJ field access demo, status=stopped]

注释字段的Spring AOP切入点表达式

1 个答案: