kagxin
commented
4 years ago Persion.java
package Persion;
public class Persion {
public String name;
private int age;
public Persion(String name, int age) {
this.name = name;
this.age = age;
}
public String info() {
return String.format("%s, age %d", this.age);
}
private String secret() {
return "secret";
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Persion{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
Student.java
package Persion;
public class Student extends Persion {
private int score;
public Student(String name, int age) {
super(name, age);
}
public String info() {
return String.format("%s, age %d", this.getName(), this.getAge());
}
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
@Override
public String toString() {
return "Student{" +
"score=" + score +
'}';
}
}
Main.java
import Persion.Persion;
public class Main {
public static void main(String[] args) throws ClassNotFoundException {
Persion xiaoming = new Persion("xiaoming", 25);
Class cls1 = Class.forName("Persion.Persion"); //通过class的完整类名
Class cls2 = Persion.class; //通过class的静态变量
Class cls3 = xiaoming.getClass(); //通过class对象获取的
System.out.println(cls1 == cls2); //ture
System.out.println(cls1 == cls3); //ture 三种方式获取的是同一个对象
}
}
Main1.java
import Persion.Persion;
import java.lang.reflect.Field;
public class Main1 {
public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
Persion xiaoming = new Persion("xiaoming", 25);
Class cls = xiaoming.getClass(); //通过class对象获取的
/*
* 获取 field的方法
* */
Field name = cls.getField("name"); // 获取指定name的public field
System.out.println(name.getName());
name.set(xiaoming, "xiaoming2"); // 使用feild设置name属性的值
Object nameStr = name.get(xiaoming); // 使用feild获取，name值
System.out.println(nameStr);
System.out.println("==================");
Field[] fields = cls.getFields(); // 获取所有的public field
for (Field field : fields) {
System.out.println(field.getName());
}
System.out.println("==================");
Field age = cls.getDeclaredField("age"); // 获取指定name的field，public protected private都可获取，获取是有方法screct
System.out.println(age.getName());
age.setAccessible(true); // 私有属性，通过该方法设置忽略权限
age.set(xiaoming, 26); //
Object val = age.get(xiaoming);
System.out.println(val);
System.out.println("==================");
Field[] declaredFields = cls.getDeclaredFields(); // 获取指定所有的field，public protected private都可获取
for (Field field : declaredFields
) {
System.out.println(field.getName());
}
System.out.println("==================");
}
}
Main2.java
import Persion.Persion;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Main2 {
public static void main(String[] args) throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
Persion xiaogang = new Persion("xiaogang", 24);
Class cls = xiaogang.getClass();
Method[] methods = cls.getDeclaredMethods(); // 获取所有方法
for (Method method : methods) {
System.out.println(method.getName());
}
System.out.println("=========");
Method secret = cls.getDeclaredMethod("secret"); // 获取private方法
secret.setAccessible(true);
Object m = secret.invoke(xiaogang); // 调用secret
System.out.println(m);
}
}
Main3.java
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Properties;
public class Main3 {
public static void main(String[] args) throws Exception {
Properties properties = new Properties();
ClassLoader classLoader = Main3.class.getClassLoader();
InputStream resourceAsStream = classLoader.getResourceAsStream("conf.properties");
properties.load(resourceAsStream);
String className = properties.getProperty("className"); // 通过配置文件获取className
String methodName = properties.getProperty("methodName"); //通过配置文件获取methodName
Class cls = Class.forName(className); //通过反射获取到Persion类关联的Class对象
System.out.println(cls.getName());
Constructor dcon = cls.getDeclaredConstructor(String.class, int.class); // 通过制定的签名获取到构造函数
Object xiaohong = dcon.newInstance("xiaohong", 22); // 通过Persion关联的Class对象，new一个Persion对象
Method ts = cls.getDeclaredMethod(methodName); // 获取到对应的Method
ts.setAccessible(true);
Object s = ts.invoke(xiaohong); //调用配置文件里的的方法
System.out.println(s);
}
}conf.properties
className=Persion.Persion
methodName=toString
Class 是java的一个特殊类
什么是反射
获取class关联的Class类对象的3种方法
代码示例
代码目录结果结构
获取class关联的Class类对象的3种方法示例
通过Class 对象操作对象字段
通过Class 对象操作对象字段
获取构造方法
ref: https://docs.oracle.com/javase/8/docs/api/index.html
反射应用示例