Java Reflection _ A simple example of changing the variables and methods in private _java

Java Reflection _ A simple example of changing the variables and methods in private

Class demotest{

 private String name= "123";

 Public GetName () {

  System.out.println (' public getName ' + name);

  return name;

 Private GetName2 () {

  System.out.println ("Private getName2" + name);

  return name;

 }

As this, change the value of name. How to change. How do I change through Java reflection

Let's take a look at how to invoke the GetName method with reflection.

Class<demotest> Calzz=demotest.class;

Constructor Cons=clazz.getconstructor (new class[]{});//This is the method of getting the class object to be constructed. parameter is an object of the class that constructs the parameter of the method.

For example, Demotest has a construction method that is public demotest (String arg0,string arg1) {...}

At this point, constructor Cons=clazz.getconstructor (new Class[]{string.class,string.class}), two string.calss correspond to ARG0,ARG1 respectively.

Next is:

Demotest test= (demotest) cons.newinstance (New object[]{});//generate the corresponding object. The parameter New object[]{} is the concrete value of the parameter corresponding to the constructor method. As just now:

demotest test= (demotest) cons.newinstance (new object[]{"Li Che", "John"});

Next:

Method Method=clazz.getmethod ("GetName", New Class[]{string.class});

Method.invoke (test,new object[]{"Harry"});

Then you can print out the King five.

How do you change the value of name as private?

1. Get field First,

Field Field=clazz.getdeclaredfield ("name");

2. Set the accessible flag of this object to the indicated Boolean value. A value of TRUE indicates that the reflected object should cancel the Java language access check when it is in use. A value of false indicates that the reflected object should implement the Java language access check.

Field.setaccessible (TRUE);

3. Modify the value of the variable

Field.set ("name", "Harry");

OK;

The same method is used to access private.

Method Method=clazz.getdeclaredmethod ("GetName2");

Method.setaccessible (true);

Method.invoke (test,new object[]{"Harry"});

You can get private and public protend protected fields with Getdeclaredfields.

If you use C.getfields (), you can only get properties of the public type

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