Field类提供访问类成员属性和值一系列方法，最常用的就是访问成员变量值和修改变量值.
众所周知,变量修饰符有pubilc,protected,default,private，修饰符提供的访问权限依次变小，private修饰的只能本类中访问，但是，通过java.lang.reflet.Field类就能访问和修改private修饰的私有变量了，example如下:
- 等待被访问Person类及其变量:
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public class Person {
public String name = "graham";
protected String sex = "男";
String province = "天津";
private int age = 26;
}
- 通过Field类的get(Object ojb)和set(Object ojb, Object value),访问和修改Person类的共私有成员:
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public class TestClass {
public String aa ="aaa";
private String bb = "bbb";
protected String cc = "ccc";
public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
Person person = new Person();
//访问公有成员用getField或者getDeclaredField
Field field = person.getClass().getField("name");
field.set(person, "grahamliu");
System.out.println(field.get(person));
//访问非公有成员必须用getDeclaredField
Field field1 = person.getClass().getDeclaredField("sex");
field1.set(person, "女");
System.out.println(field1.get(person));
Field field2 = person.getClass().getDeclaredField("province");
field2.set(person, "南极");
System.out.println(field2.get(person));
//访问和修饰private变量，必须设置setAccessible为true
Field field3 = person.getClass().getDeclaredField("age");
field3.setAccessible(true);
field3.set(person, 87);
System.out.println(field3.get(person));
//访问本类private变量，不用设置setAccessible
Field field4 = TestClass.class.getDeclaredField("cc");
System.out.println(field4.get(new TestClass()));
}
}
- 打印:
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/Library/Java/JavaVirtualMachines/jdk1.8.0_181.jdk/Contents/Home/bin/java "-javaagent:/Applications/IntelliJ IDEA
grahamliu
女
南极
87
ccc
Process finished with exit code 0
涉及2个知识点:
-
访问公有成员用getField或者getDeclaredField，访问非公有成员必须用getDeclaredField
-
访问和修饰private变量，必须设置setAccessible为true，本类除外!
