通过反射赋值

实体类

import java.util.List;

class Item {
   private String itemId;
   private String itemName;

   public String getItemId() {

       return itemId;
   }

   public void setItemId(String itemId) {

       this.itemId = itemId;
   }

   public String getItemName() {

       return itemName;
   }

   public void setItemName(String itemName) {

       this.itemName = itemName;
   }

   @Override
   public String toString() {
       return "Item [itemId=" + itemId + ", itemName=" + itemName + "]";
   }

}

public class User {

   private String id;
   private String name;
   private List<Item> items;

   public User() {
        System.out.println("User无参 ");
   }
   public User(String id,String name){
       System.out.println("User有参 id:"+id+",name:"+name);
       this.id=id;
       this.name=name;
   }

   public String getId() {

       return id;
   }

   public void setId(String id) {

       this.id = id;
   }

   public String getName() {

       return name;
   }

   public void setName(String name) {

       this.name = name;
   }

   public List<Item> getItems() {

       return items;
   }

   public void setItems(List<Item> items) {

       this.items = items;
   }

   @Override
   public String toString() {
       return "User [id=" + id + ", name=" + name + ", items=" + items + "]";
   }

}

第一个小例子

      //2.使用Java的反射机制创建对象 Class.forName("累的完整路径")
       Class<?> forName = Class.forName("com.itmayiedu.User");
       //使用默认无参构造函数对象forName.newInstance(); 使用java的反射机制创建对象
       User classUser = (User) forName.newInstance();
       classUser.setId("22");
       System.out.println(classUser);
       //创建带有参的构造函数
       Constructor<?> constructor = forName.getConstructor(String.class,String.class);
       User classUser1 = (User) constructor.newInstance("12","abc");

System.out.println(classUser1.toString());

第二个小例子
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class FanShe1 {

   public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException,
   SecurityException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException {
       //1.使用Java的反射机制获取类的所有属性方法并且为私有属性赋值
       Class<?> forName = Class.forName("com.itmayiedu.User");
       //2.获取到当前类的所有属性
       Field[] declaredFields = forName.getDeclaredFields();
       for (Field field : declaredFields) {
           System.out.println(field.getName());
       }
       System.out.println("---------------------");
       //3.获取当前类的说有方法
       Method[] declaredMethods = forName.getDeclaredMethods();
       for (Method method : declaredMethods) {
           System.out.println(method.getName());
       }
       System.out.println("---------------------");
       //4.使用Java的反射机制给私有属性赋值
       Object newInstance = forName.newInstance();
       Field fieldId = forName.getDeclaredField("id");
       //运行反射操作私有属性
       fieldId.setAccessible(true);
       fieldId.set(newInstance, "20");
       Field fieldName = forName.getDeclaredField("name");
       fieldName.setAccessible(true);
       fieldName.set(newInstance, "jjn");
       User user=(User)newInstance;
       System.out.println(user.toString());

   }
}

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