1 获取运行时类的完整结构

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2 动态创建对象

2.1 通过Class.newInstance()创建

  1. package com.lht.reflection;
  3. public class TestReflection {
  4.     public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
  5.         Class clazz = Class.forName("com.lht.reflection.User");
  6.         User user = (User) clazz.newInstance();
  7.         System.out.println(user);
  8.     }
  9. }
  11. // 实体类
  12. class User {
  13.     private String name;
  14.     private int id;
  16.     public User() {
  17.     }
  19.     public User(String name, int id) {
  20.         this.name = name;
  21.         this.id = id;
  22.     }
  24.     public String getName() {
  25.         return name;
  26.     }
  28.     public void setName(String name) {
  29.         this.name = name;
  30.     }
  32.     public int getId() {
  33.         return id;
  34.     }
  36.     public void setId(int id) {
  37.         this.id = id;
  38.     }
  40.     @Override
  41.     public String toString() {
  42.         return "com.lht.reflection.User{" +
  43.                 "name='" + name + '\'' +
  44.                 ", id=" + id +
  45.                 '}';
  46.     }
  47. }
  1. com.lht.reflection.User{name='null', id=0}

本质上Class.newInstance()调用的是User类的默认构造方法，如果将默认构造方法删除，则会报错。

2.2 通过获取类的构造器

  1. 通过Class.getDeclaredConstructor(argType1, argType2, ...)获取想要的构造器constructor
  2. 通过constructor.newInstance(arg1, arg2, ...)动态创建类实例 ```java package com.lht.reflection;

import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException;

public class TestReflection { public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException { Class clazz = Class.forName(“com.lht.reflection.User”); Constructor constructor = clazz.getDeclaredConstructor(String.class, int.class); User user = (User) constructor.newInstance(“lirt”, 210224); System.out.println(user); } }

// 实体类，同上 class User { … } ```