Spring中单例Bean依赖多例Bean的正确解决方案

た入场券 2022-12-11 04:22 126阅读 0赞

# 1 效果演示  #

public interface Person {
        void show();
    }

public class Chinese implements Person {
        private Date time;
        public void setTime(Date date) {this.time = date;}
        public void show() {
            String t = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(this.time);
            System.out.println("当前时间: " + t);
        }
    }

<?xml version="1.0" encoding="utf-8"?>
    <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns="http://www.springframework.org/schema/beans"
           xsi:schemaLocation="http://www.springframework.org/schema/beans
    	http://www.springframework.org/schema/beans/spring-beans.xsd">
        
        <bean id="chinese" class="cn.yuanyu.app.service.impl.Chinese">
            <property name="time" ref="date"/>
        </bean>
        
        <bean id="date" class="java.util.Date" scope="prototype"/>
    </beans>

@Test
    public void test_() throws InterruptedException {
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");
        Person p1 = ctx.getBean("chinese", Person.class);
        TimeUnit.SECONDS.sleep(2);
        Person p2 = ctx.getBean("chinese", Person.class);
        System.out.println("p1==p2? " + (p1 == p2));    // true
        p1.show();                                      // 当前时间: 2020-09-28 13:59:38
        TimeUnit.SECONDS.sleep(2);                      // sleep
        p2.show();                                      // 当前时间: 2020-09-28 13:59:38
    }

# 2 解决 #

## 2.1 XML ##

public interface Person {
        void show();
    }

public abstract class Chinese implements Person {
        private Date time;
        public abstract Date getTime();
        public void show() {
            Date time = getTime();
            String t = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(time);
            System.out.println("当前时间: " + t);
        }
    }

<?xml version="1.0" encoding="utf-8"?>
    <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns="http://www.springframework.org/schema/beans"
           xsi:schemaLocation="http://www.springframework.org/schema/beans
    	http://www.springframework.org/schema/beans/spring-beans.xsd">
        
        <bean id="chinese" class="cn.yuanyu.app.service.impl.Chinese">
            
            <lookup-method name="getTime" bean="date"/>
        </bean>
        
        <bean id="date" class="java.util.Date" scope="prototype"/>
    </beans>

@Test
    public void test_() throws InterruptedException {
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");
        // java.util.Date
        Date t1 = ctx.getBean("date", Date.class);
        Date t2 = ctx.getBean("date", Date.class);
        System.out.println("t1==t2? " + (t1 == t2));                // t1==t2? false
    
        Person p1 = ctx.getBean("chinese", Person.class);
        p1.show();                                                  // 当前时间: 2020-09-28 14:42:58
        TimeUnit.SECONDS.sleep(2);                                  // sleep
        Person p2 = ctx.getBean("chinese", Person.class);
        p2.show();                                                   // 当前时间: 2020-09-28 14:43:00
        System.out.println("p1==p2? " + (p1 == p2));                 // p1==p2? true
    }

## 2.2 Annotation ##

public interface Person {
        void show();
    }

public class Chinese implements Person, ApplicationContextAware {
        private ApplicationContext applicationContext;
        public void show() {
            Date date = applicationContext.getBean("date", Date.class);
            String t = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(date);
            System.out.println("当前时间: " + t);
        }
        @Override
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
            this.applicationContext = applicationContext;
        }
    }

@Configuration
    public class AppConfig {
        @Bean
        public Chinese chinese(){
            return new Chinese();
        }
        @Scope("prototype") // 多实例
        @Bean
        public Date date(){
            return new Date();
        }
    }

@Test
    public void test_() throws InterruptedException {
    
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
        Person p1 = ctx.getBean("chinese", Person.class);
        TimeUnit.SECONDS.sleep(2);
        Person p2 = ctx.getBean("chinese", Person.class);
        System.out.println("p1==p2? " + (p1 == p2));    // p1==p2? true
        p1.show();                                      // 当前时间: 2020-09-28 15:16:41
        TimeUnit.SECONDS.sleep(2);                      // sleep
        p2.show();                                      // 当前时间: 2020-09-28 15:16:43
    }

# 3 原理 #

> [https://blog.csdn.net/qq\_40306697/article/details/108339815][https_blog.csdn.net_qq_40306697_article_details_108339815]

[https_blog.csdn.net_qq_40306697_article_details_108339815]: https://blog.csdn.net/qq_40306697/article/details/108339815