如何从其他包中的类访问包私有类？ [英] How to Access package private Class from a Class in some other package?

问题描述

我有以下课程

Hello.java

package speak.hello;

import java.util.Map;

import speak.hi.CustomMap;
import speak.hi.Hi;

public class Hello {

    private Hi hi;

    Hello(Hi hi) {
        this.hi = hi;
    }

    public String sayHello() {
        return "Hello";
    }

    public String sayHi() {
        return hi.sayHi();
    }

    public Map<String, Object> getMap() {
        return hi.getMap();
    }

    public void clearMap() {
        hi.getMap().clear();
    }

    public void discardMap() {
        CustomMap map = (CustomMap) hi.getMap();
        map.discard();
    }

    public static void main(String[] args) {
        Hello hello = new Hello(new Hi());
        System.out.println(hello.sayHello());
        System.out.println(hello.sayHi());
        System.out.println(hello.getMap());
        hello.clearMap();
        System.out.println("--");
        hello.discardMap();
    }

}

Hi.java

package speak.hi;

import java.util.HashMap;
import java.util.Map;

public class Hi {
    public String sayHi() {
        return "Hi";
    }

    public Map<String, Object> getMap() {
        return new CustomMap<String, Object>();
    }
}

CustomMap.java

package speak.hi;

import java.util.HashMap;

public class CustomMap<K, V> extends HashMap<K, V> {
    private static final long serialVersionUID = -7979398843650044928L;

    public void discard() {
        System.out.println("Discarding Map");
        this.clearCache();
        this.clear();
    }

    @Override
    public void clear() {
        System.out.println("Clearing Map");
        super.clear();
    }

    private void clearCache() {
        System.out.println("Clearing Map");
    }
}

这一切正常，直到我删除 public 访问说明符来自 CustomMap

This works fine until I remove public access specifier from CustomMap

package speak.hi;

import java.util.HashMap;

class CustomMap<K, V> extends HashMap<K, V> {
    private static final long serialVersionUID = -7979398843650044928L;

    public void discard() {
        System.out.println("Discarding Map");
        this.clearCache();
        this.clear();
    }

    @Override
    public void clear() {
        System.out.println("Clearing Map");
        super.clear();
    }

    private void clearCache() {
        System.out.println("Clearing Map");
    }
}

编译器大喊

类型speak.hi.CustomMap不是可见

现在如果我没有选项来修改 speak.hi.CustomMap （第三方jar等等）。有什么方法我仍然可以使用 CustomMap 来自 speak.hello.Hello ？

Now If I don't have options to modify speak.hi.CustomMap (third party jar etc..) Is there any way I could still use CustomMap from speak.hello.Hello?

我知道的一个选择是将 speak.hello.Hello 移至 speak.hi.Hello as Now Hello在包 speak.hi 它可以访问包私有类您好

One option that I know is to move speak.hello.Hello to speak.hi.Hello as Now Hello is in package speak.hi it can access package private Class Hi

还有其他办法吗？也许使用反射？

Is there any other way to do this ? Using reflection perhaps ?

编辑：根据@StephenC的要求更新了其他详细信息

EDIT :Updated with additional details as requested by @StephenC

推荐答案

以下方法调用默认使用反射的范围类方法

Following method Invokes default scoped class method using reflection

public void discardMap() {
    //CustomMap map = (CustomMap) hi.getMap();
    //map.discard();
    try {
        Object o =hi.getClass().getMethod("getMap").invoke(hi);
        Method m = o.getClass().getMethod("discard");
        m.setAccessible(true);
        m.invoke(o);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

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