反射机制学习笔记.doc

Java反射机制学习笔记1. 运行时利用带参构造方法生成类实例a) 利用Constructor的newInstance()方法，首先准备一个Class数组作为Constructor的参数类型，然后调用Class对象的getConstructor()方法获得一个专属的Constructor对象，最后再准备一个Object作为Constructor对象newInstance()方法的实参/ 利用反射构造带参数的类的实例/ 得到类实例Class clazz = Class.forName(User.class.getName();Class paramType = new Class String.class, int.class, String.class ;/ 得到构造方法Constructor constructor = clazz.getConstructor(paramType);/ 实例构造方法的参数数组Object params = new Object Paulz, 29, 111111 ;/ 利用带参构造方法实例类Object obj = constructor.newInstance(params);System.out.println(User) obj).getUserName();/结果：Paulz2. 运行时给属性赋值和调用方法,copy一个实体类，并输出源对象的和copy对象public static Object copy(Object obj) throws Exception / 获得对象的类型Class clazz = obj.getClass();System.out.println(该对象的类型是 = + clazz.getName();/ 通过默认构造方法创建一个新的对象,视其参数动态决定调用哪个构造函数Object objectCopy = clazz.getConstructor(new Class ).newInstance(new Object );/ 获得对象的所有属性，包括私有属性Field fields = clazz.getDeclaredFields();for (int i = 0; i fields.length; i+) Field field = fieldsi;/ 获得数组中对应的属性名称String fieldName = field.getName();/ 获得相应属性的getter和setter方法名称String letter = fieldName.substring(0, 1).toUpperCase(); String getName = get + letter + fieldName.substring(1); String setName = set + letter + fieldName.substring(1);/ 获得相应的getter和setter方法Method getMethod = clazz.getMethod(getName, new Class );Method setMethod = clazz.getMethod(setName, new Class field.getType() );/ 调用源对象的getter方法Object value = getMethod.invoke(obj, new Object );System.out.println(value = + value);/ 调用copy的setter方法，将源对象值赋给新对象对应的方法setMethod.invoke(objectCopy, new Object value );return objectCopy;源实体类public class User private String userName;private int age;public String password;public String getPassword() return password;public void setPassword(String password) this.password = password;private String get() return Paulz;public User(String userName, int age, String password) this.userName = userName;this.age = age;this.password = password;public User() public String getUserName() return userName;public void setUserName(String userName) this.userName = userName;public int getAge() return age;public void setAge(int age) this.age = age;Overridepublic String toString() return Name = + this.userName + | age = + this.age+ | Password = + this.password + ;测试方法：public static void main(String args)/ 运行时调用方法，copy一个新的对象User user1 = new User(罗专, 28, 111111);Object object = copy(user1);System.out.println(user1);System.out.println(object);3. 根据反射来动态创建一个数组Class type = String.class;/ 指定数组的大小和类型Object array = Array.newInstance(type, 5);/ 对索引为2的位置赋值Array.set(array, 2, Hello);/ 取索引为2的地方的值String s = (String) Array.get(array, 2);System.out.printl