反射10

package com.imooc.reflect;import java.lang.reflect.Method;public class MethodDemo1 {public static void main(String[] args) {   //要获取print(int ,int )方法  1.要获取一个方法就是获取类的信息，获取类的信息首先要获取类的类类型A a1 = new A();Class c = a1.getClass();/* * 2.获取方法 名称和参数列表来决定   * getMethod获取的是public的方法 * getDelcaredMethod自己声明的方法 */    try {
//Method methodOne =  userInfo.getDeclaredMethod("childMehtod",int.class);               //访问私有方法添加权限 调用private方法的关键一句话              //methodOne.setAccessible(true);
//Method m =  c.getMethod("print", new Class[]{int.class,int.class});    Method m = c.getMethod("print", int.class,int.class);        //方法的反射操作      //a1.print(10, 20);方法的反射操作是用m对象来进行方法调用 和a1.print调用的效果完全相同        //方法如果没有返回值返回null,有返回值返回具体的返回值    //Object o = m.invoke(a1,new Object[]{10,20});    Object o = m.invoke(a1, 10,20);    System.out.println("==================");    //获取方法print(String,String)             Method m1 = c.getMethod("print",String.class,String.class);             //用方法进行反射操作             //a1.print("hello", "WORLD");             o = m1.invoke(a1, "hello","WORLD");             System.out.println("===================");           //  Method m2 = c.getMethod("print", new Class[]{});                Method m2 = c.getMethod("print");               // m2.invoke(a1, new Object[]{});                m2.invoke(a1);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}      }}class A{public void print(){System.out.println("helloworld");}public void print(int a,int b){System.out.println(a+b);}public void print(String a,String b){System.out.println(a.toUpperCase()+","+b.toLowerCase());}}
package com.imooc.reflect;import java.io.BufferedReader;import java.io.InputStreamReader;import java.lang.reflect.Method;public class MethodDemo2 {public static void main(String[] args) {UserService us = new UserService();/* * 通过键盘输入命令执行操作 * 输入update命令就调用update方法 * 输入delete命令就调用delete方法 * ... */try {BufferedReader br = new BufferedReader(new InputStreamReader(System.in));System.out.println("请输入命令:");String action = br.readLine();/*if("update".equals(action)){us.update();}if("delete".equals(action)){us.delete();}if("find".equals(action)){us.find();}*//* * action就是方法名称， 都没有参数--->通过方法的反射操作就会简单很多 * 通过方法对象然后进行反射操作 */Class c = us.getClass();Method m = c.getMethod(action);m.invoke(us);} catch (Exception e) {e.printStackTrace();}}}

package com.imooc.reflect;public class MethodDemo3 {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubUser u1 = new User("zhangsan", "123456", 30);System.out.println(BeanUtil.getValueByPropertyName(u1, "username"));       System.out.println(BeanUtil.getValueByPropertyName(u1, "userpass"));}  }
package com.imooc.reflect;import java.lang.reflect.Method;public class BeanUtil {/** * 根据标准javaBean对象的属性名获取其属性值 *  * @param obj * @param propertyName * @return */public static Object getValueByPropertyName(Object obj, String propertyName) {// 1.根据属性名称就可以获取其get方法String getMethodName = "get"+ propertyName.substring(0, 1).toUpperCase()+ propertyName.substring(1);//2.获取方法对象Class c = obj.getClass();try {//get方法都是public的且无参数Method m= c.getMethod(getMethodName);//3 通过方法的反射操作方法Object value = m.invoke(obj);return value;} catch (Exception e) {e.printStackTrace();return null;}}}

package com.imooc.reflect;import java.lang.reflect.Method;import java.util.ArrayList;public class MethodDemo4 {public static void main(String[] args) {ArrayList list = new ArrayList();ArrayList<String> list1 = new ArrayList<String>();list1.add("hello");//list1.add(20);错误的Class c1 = list.getClass();Class c2 = list1.getClass();System.out.println(c1 == c2);//反射的操作都是编译之后的操作/* * c1==c2结果返回true说明编译之后集合的泛型是去泛型化的 * Java中集合的泛型，是防止错误输入的，只在编译阶段有效， * 绕过编译就无效了 * 验证：我们可以通过方法的反射来操作，绕过编译 */try {Method m = c2.getMethod("add", Object.class);m.invoke(list1, 20);//绕过编译操作就绕过了泛型System.out.println(list1.size());System.out.println(list1);/*for (String string : list1) {System.out.println(string);}*///现在不能这样遍历} catch (Exception e) {  e.printStackTrace();}}}
package com.imooc.reflect;//标准的JavaBean类有私有属性都对应有get/set方法，有无参数的构造方法public class User {private String username;private String userpass;private int age;public User(){}public User(String username, String userpass, int age) {super();this.username = username;this.userpass = userpass;this.age = age;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getUserpass() {return userpass;}public void setUserpass(String userpass) {this.userpass = userpass;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}
package com.imooc.reflect;public class UserService {public void delete(){System.out.println("删除用户");}public void update(){System.out.println("修改用户");}public void find(){System.out.println("查找用户");}}