Java - 获取传递给方法的参数? [英] Java - Get arguments passed to a method?

问题描述

是否可以使用反射 api 将参数传递给 Java 中的方法?

Is it possible to get arguments pass to a method in Java using reflection api?

是否可以使用像 AspectJ 这样的 AOP 库来实现这一点?

Is it possible to achieve this using AOP libraries like AspectJ?

我在 Android 上运行.

I am running on Android.

public abstract class Base {

   public void printArguments() {

      //Here I need to get access to arg1, arg2, arg3
   }

}

.

public class MyClass extends Base {

   public void (String arg1, Integer arg2, String arg3) {

      super.printArguments();      
   }
}

推荐答案

是否可以使用像 AspectJ 这样的 AOP 库来实现这一点?

Is it possible to achieve this using AOP libraries like AspectJ?

是的，当然.这是 AspectJ 中典型的初学者练习，如下所示:

Yeah, sure. This is kind of the typical beginner's exercise in AspectJ, like so:

public class SampleClass {
    public SampleClass() { super(); }
    public SampleClass(String s) { this(); }
    public SampleClass(int i) { this(); }
    public void method01(String s, Number n, Throwable t) {}
    public void method02(int i, String s, double d) {}
    public void method03(String s) {}
    public void method04() {}
    public void method05(String s, Number n, double d) {}

    public static void main(String[] args) {
        new SampleClass().method01("foo", new Integer(11), new RuntimeException("error"));
        new SampleClass("test").method02(11, "bar", Math.PI);
        new SampleClass(123).method03("zot");
        new SampleClass("another test").method04();
        new SampleClass(456).method05("baz", new Integer(11), Math.E);
    }
}

现在您只需要编写一个方面来拦截所有方法执行(以及可选的构造函数执行，如下所示):

Now you just need to write an aspect which intercepts all your method executions (and optionally also constructor executions, as shown below):

public aspect MethodArgsAspect {
    pointcut allMethods()      : execution(* *(..));
    pointcut allConstructors() : execution(*.new(..));

    before() : !within(MethodArgsAspect) && (allMethods() || allConstructors()) {
        System.out.println(thisJoinPointStaticPart.getSignature());
        for (Object arg : thisJoinPoint.getArgs())
            System.out.println("    " + arg);
    }
}

当运行SampleClass.main时，这个aspect会打印:

When running SampleClass.main, this aspect will print:

void SampleClass.main(String[])
    [Ljava.lang.String;@7fdcde
SampleClass()
void SampleClass.method01(String, Number, Throwable)
    foo
    11
    java.lang.RuntimeException: error
SampleClass()
SampleClass(String)
    test
void SampleClass.method02(int, String, double)
    11
    bar
    3.141592653589793
SampleClass()
SampleClass(int)
    123
void SampleClass.method03(String)
    zot
SampleClass()
SampleClass(String)
    another test
void SampleClass.method04()
SampleClass()
SampleClass(int)
    456
void SampleClass.method05(String, Number, double)
    baz
    11
    2.718281828459045

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