Java：当方法明显存在时，NoSuchMethodException

问题描述

在我目前的项目中，我觉得有必要使用反射在Java中创建一种模拟回调系统。但是，我遇到了让我的反思真正起作用的问题。错误的代码如下：

On my current project, I've felt the need to create a sort of simulated callback system in Java using reflection. However, I'm having issues getting my reflection to actually function. The code at fault follows:

public Callback(Object parentObj, String methodName, Class<?>...parameters)
{
    if(parentObj == null)
        throw new IllegalArgumentException("parentObj cannot be null", new NullPointerException());

    Class<?> clazz = parentObj.getClass();

    // Trace debugging, see output
    for(Method m : clazz.getDeclaredMethods())
        if(m.getName().equals("myMethod")) System.out.println (m);

    try { this.method = clazz.getMethod(methodName, parameters); }
    catch(NoSuchMethodException nsme) { nsme.printStackTrace(); } // Exception caught
    catch(SecurityException se) { se.printStackTrace(); }

    this.parentObj = parentObj;
    this.parameters = parameters;
}

当我构建回调对象，我正在使用这样的语法：

When I construct the Callback object, I'm using syntax like this:

new Callback(this, "myMethod", boolean.class)

当我尝试创建我的伪回调时，它会遇到 NoSuchMethodException catch block。我在上面包含了一些跟踪调试，以显示我的一个方法的输出失败。输出：

When I try to create my pseudo-callback, it hits the NoSuchMethodException catch block. I've included some trace debugging above to show the output of one of my methods failing. The output:

private void my.package.MyClass.myMethod(boolean)
java.lang.NoSuchMethodException: my.package.MyClass.myMethod(boolean)
    at java.lang.Class.getMethod(Class.java:1605)
    at my.package.other.Callback.<init>(Callback.java:63)

我无法解决问题，所以我开始打猎，但收效甚微。我能找到的最好的是提到编译的JAR和运行时之间的版本冲突。但是， MyJar.jar / META-INF / MANIFEST.MF 包含创建者：1.6.0_02（Sun Microsystems Inc.）。我的IDE正在运行 C：\Program Files \ Java \ jdk1.6.0_02 \bin\javac.exe 来编译我的项目。我正在使用 C：\Program Files \Java \ jdk1.6.0_02 \bin\java.exe 来运行我的JAR。

I couldn't figure the problem out, so I started hunting, to little avail. The best I could find was mention of versioning conflict between the compiled JAR and the runtime. However, MyJar.jar/META-INF/MANIFEST.MF contains Created-By: 1.6.0_02 (Sun Microsystems Inc.). My IDE is running C:\Program Files\Java\jdk1.6.0_02\bin\javac.exe to compile my project. I'm using C:\Program Files\Java\jdk1.6.0_02\bin\java.exe to run my JAR.

我很遗憾为什么 Class.getMethod 声称该方法不存在，但是 Class .getMethods 似乎没有问题找到它。救命？ :(

I'm at a loss why Class.getMethod is claiming the method doesn't exist, but Class.getMethods seems to have no problem finding it. Help? :(

推荐答案

您的方法是私有的，但 getMethod（）仅返回公共方法。

Your method is private but getMethod() only returns public method.

您需要使用 getDeclaredMethod（）。

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