注解的实例

た入场券 2022-04-12 05:43 199阅读 0赞

自从学习注解以来，应该都会有这么一个疑问，注解到底有什么用，为什么需要注解。我觉得注解的用处在于提取注解中的值进行某些功能性验证。  
直接上代码：  
**需求：interspace管理系统，功能1.查看照片2.发表说说3.对话框对话。并且设置用户权限。**

1.  Users类
2.  Function类 写 1.查看照片2.发表说说3.对话框对话。
3.  Permission 注解 设置权限
4.  Test01测试类

Users类

package com.SiyualChen.day04.homeWork.test01;
    
    import com.SiyualChen.day03.userSystem.User;
    
    import java.util.ArrayList;
    import java.util.Objects;
    
    public class Users {
        private String username;
        private String password;
        private ArrayList<String> list;
    
        public ArrayList<String> getList() {
            return list;
        }
    
        public void setList(ArrayList<String> list) {
            this.list = list;
        }
    
        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            Users users = (Users) o;
            return Objects.equals(username, users.username) &&
                    Objects.equals(password, users.password);
        }
    
        @Override
        public int hashCode() {
            return Objects.hash(username, password);
        }
    
        @Override
        public String toString() {
            return "Users{" +
                    "username='" + username + '\'' +
                    ", password='" + password + '\'' +
                    '}';
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getPassword() {
            return password;
        }
    
        public void setPassword(String password) {
            this.password = password;
        }
    
        public Users() {
        }
    
        public Users(String username, String password) {
            this.username = username;
            this.password = password;
        }
    }

Function：

package com.SiyualChen.day04.homeWork.test01;
    
    public class Function {
        @Permission(value = "lookPhoto")
        public void lookPhoto(){
            System.out.println("偷看女神相册");
        }
        @Permission(value = "publishLog")
        public void publishLog(){
            System.out.println("发表一篇日志，等待女神点赞");
        }
        @Permission(value = "talkWithHer")
        public void talkWithHer(){
            System.out.println("和女神聊骚");
        }
    }

Permission 注解

package com.SiyualChen.day04.homeWork.test01;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Permission {
        String value();
    }

Test01：

package com.SiyualChen.day04.homeWork.test01;
    
    
    
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.util.ArrayList;
    import java.util.Scanner;
    
    public class Test01 {
        public static void main(String[] args) throws NoSuchMethodException, ClassNotFoundException, IllegalAccessException, InvocationTargetException, InstantiationException {
            ArrayList<Users> userList = new ArrayList<>();
            Users users1 = new Users();
            users1.setUsername("chenchen");
            users1.setPassword("123456");
            ArrayList<String> list1 = new ArrayList<>();
            list1.add("lookPhoto");
            list1.add("publishLog");
            users1.setList(list1);
            userList.add(users1);
    
            Users users2 = new Users();
            users2.setUsername("sisi");
            users2.setPassword("123456");
            ArrayList<String> list2 = new ArrayList<>();
            list2.add("publishLog");
            list2.add("talkWithHer");
            users2.setList(list2);
            userList.add(users2);
    
            Users users3 = new Users();
            users3.setUsername("yuanyuan");
            users3.setPassword("123456");
            ArrayList<String> list3 = new ArrayList<>();
            list3.add("publishLog");
            users3.setList(list3);
            userList.add(users3);
           // System.out.println(userList);
    
    
            Scanner sc = new Scanner(System.in);
            System.out.println("请输入您的账号");
            String username = sc.next();
            System.out.println("请输入您的密码");
            String password = sc.next();
            Users u =null;
            for (int i = 0; i < userList.size(); i++) {
                if (userList.get(i).getUsername().equals(username) &&userList.get(i).getPassword().equals(password)){
                    System.out.println("登陆成功，请选择您的项目：1.lookPhoto  2.publishLog 3.talkWithHer");
                    u=userList.get(i);
                    String choose = sc.next();
                    Function function = new Function();
                    switch (choose){
                        case "1":
                            method("lookPhoto",u);
                            //function.lookPhoto();
                            //System.out.println("lookPhoto");
                            break;
                        case "2":
                            method("publishLog",u);
                            //function.publishLog();
                            //System.out.println("publishLog");
                            break;
                        case "3":
                            method("talkWithHer",u);
                            //function.talkWithHer();
                            //System.out.println("talkWithHer");
                            break;
                        default:
                            System.out.println("您输入的项目有误，暂时未开发这个功能");
                            break;
                    }
    
                }
    
    
    
            }
            if (u==null){
                System.out.println("账号密码错误，请重新输入");
            }
    
    
    
    
        }
        public static void method(String method,Users u) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException {
            //我现在是需要拿方法名上的注解，value  和  集合中的数据进行比较
            Class<?> aClass = Class.forName("com.SiyualChen.day04.homeWork.test01.Function");
            Method declaredMethod = aClass.getDeclaredMethod(method);
            Object obj = aClass.newInstance();
            Permission annotation = declaredMethod.getAnnotation(Permission.class);
            String value = annotation.value();
            if (u.getList().contains(value)){
                declaredMethod.invoke(obj);
            }else{
                System.out.println("您没有访问权限");
            }
    
    
        }
    }

请输入您的账号
    chenchen
    请输入您的密码
    123456
    登陆成功，请选择您的项目：1.lookPhoto  2.publishLog 3.talkWithHer
    3
    您没有访问权限
    
    Process finished with exit code 0