@interface反射赋值

向右看齐 2022-09-02 11:53 109阅读 0赞

定义一个Autowired接口

package com.biaodian.myface;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.FIELD)
    public @interface Autowired {
    }

定义两个service

package com.biaodian.service;
    
    public class HelloService {
    }
    
    
    
    
    package com.biaodian.service;
    
    public class UserService {
    }

定义一个controller

package com.biaodian.controller;
    
    import com.biaodian.myface.Autowired;
    import com.biaodian.service.HelloService;
    import com.biaodian.service.UserService;
    
    public class HelloController {
        @Autowired
        private HelloService helloService;
    
        @Autowired
        private UserService userService;
    
        public HelloService getHelloService() {
            return helloService;
        }
        public UserService getUserService() {
            return userService;
        }
    }

在main方法赋值

import com.biaodian.controller.HelloController;
    import com.biaodian.myface.Autowired;
    
    import java.lang.reflect.Field;
    
    public class Main {
    
        public static void main(String[] args) throws IllegalAccessException, InstantiationException {
            //先获取类的class
            Class<HelloController> helloControllerClass = HelloController.class;
            //根据class生产类对象
            HelloController helloController = helloControllerClass.newInstance();
            //获取class的属性遍历
            for (Field declaredField : helloControllerClass.getDeclaredFields()) {
                //判断属性上是否有Autowired注解
                Autowired annotation = declaredField.getAnnotation(Autowired.class);
                if (annotation!=null){
                    //私有属性时也可访问
                    declaredField.setAccessible(true);
                    //有，先获取该属性的class
                    Class<?> type = declaredField.getType();
                    //根据class获取类对象
                    Object o = type.newInstance();
                    //把该对象设置到helloController中
                    declaredField.set(helloController,o);
                }
            }
            System.out.println(helloController.getUserService());
            System.out.println(helloController.getHelloService());
        }
    }

输出打印结果

com.biaodian.service.UserService@511d50c0
    com.biaodian.service.HelloService@60e53b93
    
    Process finished with exit code 0