Java基础系列：反射修改对象属性 |
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1 应用场景
利用反射，通过对象（类实例化）属性名称，修改对象（类实例化）属性的值。 此处感谢：TD_FAlmK。 2 修改类属性值 2.1 实体类 package com.company.designpattern.reflect; import java.util.Objects; /** * 测试类，用于反射测试 * @author xindaqi * @since 2020-11-26 */ public class User { private String name; private String address; private Integer age; public User() {} public User(String name, String address, Integer age) { this.name = name; this.address = address; this.age = age; } @Override public boolean equals(Object o) { if(this == o) { return true; } if(null == o || getClass() != o.getClass()) { return false; } User that = (User) o; return name.equals(that.name) && address.equals(that.address) && age == that.age; } @Override public int hashCode() { return Objects.hash(name, address, age); } public void setName(String name) { this.name = name; } public String getName() { return name; } public void setAddress(String address) { this.address = address; } public String getAddress() { return address; } public void setAge(Integer age) { this.age = age; } public Integer getAge() { return age; } @Override public String toString() { return "User:{" + "name: " + name + "address: " + address + "age: " + age + "}"; } } 2.1 暴力修改 package com.company.designpattern.reflect; import java.beans.PropertyDescriptor; import java.lang.reflect.Field; import java.lang.reflect.Method; /** * 反射测试 * @author xindaqi * @since 2020-11-26 */ public class ReflectTest { public static void main(String[] args) throws Exception { /** * 类实例化 */ User user = new User("xiaoxiao", "shenzhen", 10); /** * 反射获类 */ Class clazz = user.getClass(); /** * 获取类中所有属性 */ Field[] fields = clazz.getFields(); System.out.println("Methods in Class: " + fields); /** * 获取某个属性方法 * 如name属性的方法 */ Field field = clazz.getDeclaredField("name"); /** * 开启私有属性编辑权限 */ field.setAccessible(true); /** * 设置属性值 */ field.set(user, "dada"); Class s = field.getType(); System.out.println("data type: " + s); System.out.println("Object name: " + field.getName()); System.out.println("暴力赋值: " + user.getName()); } } 2.2 内省机制修改 package com.company.designpattern.reflect; import java.beans.PropertyDescriptor; import java.lang.reflect.Field; import java.lang.reflect.Method; /** * 反射测试 * @author xindaqi * @since 2020-11-26 */ public class ReflectTest { public static void main(String[] args) throws Exception { /** * 类实例化 */ User user = new User("xiaoxiao", "shenzhen", 10); /** * 反射获类 */ Class clazz = user.getClass(); /** * 内省机制 */ PropertyDescriptor propertyDescriptor = new PropertyDescriptor("name", clazz); Method setMethod = propertyDescriptor.getWriteMethod(); setMethod.invoke(user, "erer"); System.out.println("内省机制: " + user.getName()); } } 3 小结 3.1 暴力修改暴力修改private属性值，需要使用setAccessable(true)方法获取修改权限，否则会出现如下情况： Exception in thread “main” java.lang.IllegalAccessException: Class com.company.designpattern.reflect.ReflectTest can not access a member of class com.company.designpattern.reflect.User with modifiers “private” at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:102) at java.lang.reflect.AccessibleObject.slowCheckMemberAccess(AccessibleObject.java:296) at java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:288) at java.lang.reflect.Field.set(Field.java:761) at com.company.designpattern.reflect.ReflectTest.main(ReflectTest.java:39) 3.2 内省模式通过PropertyDescriptor获取属性类实例，调用getWriteMethod()获取属性的写方法，invoke即可设定属性值。 【参考文献】 [1] [2] |
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