Aspectj 可选参数绑定

Question

我希望 Aspectj 使用 args 绑定我的方法参数。

像这样：

    @Before("@annotation(authorized) && args(java.util.String)")
    public void authorize(JoinPoint joinPoint, Authorized authorized, String str)

但是，我不能指望字符串参数存在。我希望将建议应用于使用该注释的所有方法，而不仅仅是带有 String 参数的方法。

如果建议的方法没有 String 参数，我希望 str 填充空值。这可能吗？或者是使用 joinPoint.getArgs() 的唯一选项？

Answer 1

您可以使用 getArgs()，另一种方法是创建多个委托给您要执行的功能的建议：

@Before("@annotation(authorized) && execution(* *())") // no string
public void authorize(JoinPoint joinPoint, Authorized authorized) {
  helper(joinPoint,authorized,null);
}

// 1 argument, which is the string
@Before("@annotation(authorized) && execution(* *(..)) && args(str)") 
public void authorize(JoinPoint joinPoint, Authorized authorized, String str) {
  helper(joinPoint,authorized,str);
}

请注意，我还包括一个执行切入点元素。包括这一点可能很重要。否则，如果使用纯 AspectJ 编译，没有它的切入点可能会同时匹配方法的调用和执行连接点，运行建议两次。

Answer 2

I have an answer to the question you asked in the comment to Andy's answer:

Would it be possible to advice methods with unknown amount of arguments, but not ending with an argument of a specific type?

package de.scrum_master.app;

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

@Retention(RetentionPolicy.RUNTIME)
public @interface Authorized {}

package de.scrum_master.app;

public class Application {
    @Authorized static void bla(String string, int i, int j) {}
    @Authorized static void baz(String string, int i, Integer integer) {}
    @Authorized static void zot(String string) {}
    @Authorized static void bar(Integer integer) {}
    @Authorized static void foo() {}

    public static void main(String[] args) {
        foo();
        bar(new Integer(11));
        zot("xxx");
        baz("yyy", 123, new Integer(22));
        bla("zzz", 123, 456);
    }
}

package de.scrum_master.aspect;

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

import de.scrum_master.app.Authorized;

@Aspect
public class MyAspect {
    @Before("@annotation(authorized) && execution(* *(..)) && !execution(* *(.., Integer))")
    public void authorize(JoinPoint joinPoint, Authorized authorized) {
        System.out.println(joinPoint);
    }
}

Console output:

execution(void de.scrum_master.app.Application.foo())
execution(void de.scrum_master.app.Application.zot(String))
execution(void de.scrum_master.app.Application.bla(String, int, int))

As you can see, the two methods baz and bar not ending with a certain type - Integer in this example - are excluded from matching.

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