反射

反射访问私有属性、方法

包含私有属性、方法的类

public class privateObject {
    private String privateStr = "this is a privateSting";
    public void setPrivateStr(String str) {
        this.privateStr = str;
    }
    private void printPrivateStr() {
        System.out.println(this.privateStr);
    }
    private void printParmas(int param1, int param2) {
        System.out.println(param1);
        System.out.println(param2);
    }
}

测试类

package example;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class TestMain {
    public static void main(String[] args) throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException, NoSuchMethodException, InvocationTargetException {
        // 访问私有属性
        privateObject privateObject = new privateObject();
        Field privateStringField = privateObject.getClass().getDeclaredField("privateStr");
        privateStringField.setAccessible(true);
        System.out.println((String) privateStringField.get(privateObject));
        // 访问私有方法
        Method privateObjectMethod = privateObject.getClass().getDeclaredMethod("printPrivateStr", null);
        privateObjectMethod.setAccessible(true);  
        privateObjectMethod.invoke(privateObject, null);
        // 访问带参数的私有方法
        Class[] cArg = new Class[2];
        cArg[0] = int.class;
        cArg[1] = int.class;
        Method privateObjectMethod2 = privateObject.getClass().getDeclaredMethod("printParmas", cArg);
        privateObjectMethod2.setAccessible(true);
        privateObjectMethod2.invoke(privateObject, 1, 2);
    }
}

注意：

privateObjectMethod2.setAccessible(true);用于设置语言检查访问（public/private/protect/default），true为关闭，false为打开。