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Java反射获取内部类有局限
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这周接触到继承及修改具有包访问权的内部类内容，略梳理了下各种资料，发觉在包外修改内部类内容必须通过实例.......
网上关于这部分的内容比较少，参考了下这位的帖子：http://blog.csdn.net/helloapps/article/details/5716604
反射里的Class, Field, Method, Constructor都是S物，必须结合对象使用，除非是静态的。
获取非public对象须用类似getDeclaredMethod()而不是getMethod()。
Field和Method都能设置accessible(true)，之后能访问到私有权限。
这里贴的两个类，放在不同包里，能通过内部类实例修改其成员，也能使用内部类构造函数新建实例....但是还不清楚能否进一步到能修改内部类函数里的变量？
Outer class and inner class:
package ee.test1;public class OuterClass { private Inner2 inn2 = new Inner2(); public static final int PUBLIC_STATIC_NUMBER = 100;
static int DEFAULT_STATIC_NUMBER = 200;
public int PUBLIC_NUMBER = 300;
protected int PROTECTED_NUMBER = 400;
private int PRIVATE_NUMBER = 500; private String str[] = {"Str1", "Str2", "Str3"}; public Runnable ta = new Runnable() {
public void run() {
System.out.println("Method in anonymous class is executed!");
}
}; private class Inner2 {
String ta2; public Inner2() {
ta2 = "A";
System.out.println("Inner2 is instantiated!");
} public void p2() {
System.out.println("ta2: " + ta2);
}
} class Inner3 {
public Inner3() {
System.out.println("Inner2 is instantiated!");
}
} public class Inner1 {
public Inner1() {
System.out.println("Inner1 is instantiated!");
}
}
}
Test：
package ff.test2;import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;import ee.test1.OuterClass;public class ReflectInnerTest { public static void main(String args[]) {
OuterClass ric = new OuterClass();
try {
reflectInner(ric);
} catch (Exception e) {
e.printStackTrace();
}
} private static void reflectInner(OuterClass ric)
throws InstantiationException, IllegalAccessException,
SecurityException, NoSuchMethodException, IllegalArgumentException,
InvocationTargetException, ClassNotFoundException,
NoSuchFieldException {
Class<? extends OuterClass> clazz = ric.getClass(); // anonymous class has NO constructor, cannot create instant or access
// method
// but could access the method and member as follows:
Runnable r = (Runnable) (clazz.getField("ta").get(ric));
r.run(); // Below to access inner class via its member.
Field f2 = clazz.getDeclaredField("inn2");
f2.setAccessible(true);
Class<?> cls = f2.getType();
Field f3 = cls.getDeclaredField("ta2");
f3.setAccessible(true);
Method m2 = cls.getDeclaredMethod("p2", null);
m2.setAccessible(true);
// f2.get(ric) (== ric.inn2) is to get the inn2 instant(which is Outer's
// member)
m2.invoke(f2.get(ric), null); // get original value
f3.set(f2.get(ric), "C"); // change it at run-time
m2.invoke(f2.get(ric), null); // show the value again Field field1 = clazz.getDeclaredField("PUBLIC_STATIC_NUMBER");
field1.setAccessible(true);
System.out.println(field1.getInt(null)); Field field2 = clazz.getDeclaredField("DEFAULT_STATIC_NUMBER");
field2.setAccessible(true);
System.out.println(field2.getInt(null)); Field field3 = clazz.getDeclaredField("PUBLIC_NUMBER");
field3.setAccessible(true);
System.out.println(field3.getInt(ric)); Field field4 = clazz.getDeclaredField("PROTECTED_NUMBER");
field4.setAccessible(true);
System.out.println(field4.getInt(ric)); Field field5 = clazz.getDeclaredField("PRIVATE_NUMBER");
field5.setAccessible(true);
System.out.println(field5.getInt(ric)); Field field6 = clazz.getDeclaredField("str");
field6.setAccessible(true);
System.out.println(((String[]) field6.get(ric))[0]);
System.out.println(Array.get(field6.get(ric), 1)); // ----------------------------------------
// Below gets the array of inner classes
Class<?> classes[] = clazz.getDeclaredClasses();
for (Class<?> c : classes) {// Reflect on member classes
int i = c.getModifiers();
String s = Modifier.toString(i);
if (s.contains("static"))// handle static inner class
c.getConstructor().newInstance();
else {
// instantiate inner classes
Constructor cons = c.getDeclaredConstructor(ric.getClass());
cons.setAccessible(true);
Object c1 = cons.newInstance(ric);
if (c.getSimpleName().equals("Inner2")) {
Method m = c.getDeclaredMethod("p2", null);
m.setAccessible(true);
m.invoke(c1, null);
Field f = c.getDeclaredField("ta2");
f.setAccessible(true);
f.set(c1, "B");
m.invoke(c1, null);
}
}
}
// -------------------------------------------------
}
}
