Spring基于Java注解的配置

忘是亡心i 2022-07-11 11:22 169阅读 0赞

前面已经讲了自动扫包配置和基于XML的配置，这一节讲基于Java的配置

（1）entity  
厨师类，增加了唯一id

package spring.ch2.topic8;
    
    import org.springframework.beans.factory.annotation.Value;
    
    /** * Created by louyuting on 17/1/23. */
    public class Chief { 
        private final int id = index++;
    
        private static int index = 0;
    
        public int getId() {
            return id;
        }
    
        @Value("jack")
        private String name = "";
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    }

SpringBeans类：主要用来创建各种bean:

package spring.ch2.topic8;
    
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    /** * Created by louyuting on 17/1/23. */
    @Configuration
    public class SpringBeans { 
        @Bean
        public Chief jack() {
            Chief chief = new Chief();
            chief.setName("mike");
            return chief;
        }
    }

@Configuration 代表这是一个配置文件，  
@Bean跟我们之前用的 XML中的bean标签是一致的。

基于java的配置有一个好处，就是在注入属性值的时候更加直观，不再是用property/>标签

（2）配置文件：只有一个自动扫包。

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:util="http://www.springframework.org/schema/util" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
    
        <context:component-scan base-package="spring.ch2.topic8" />
    </beans>

（3）测试类;

package spring.ch2.topic8;
    
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.context.ApplicationContext;
    import org.springframework.test.context.ContextConfiguration;
    import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    
    /** * Created by louyuting on 17/1/20. */
    @RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration(locations = {
       "/spring/ch2/topic8/ApplicationContext-test.xml"})
    public class ChiefTest { 
        @Autowired
        private ApplicationContext applicationContext;
    
        @Test
        public void testChief(){
            Chief jack1 = (Chief)applicationContext.getBean(Chief.class);
            System.out.println(jack1.getId());
    
            Chief jack = (Chief)applicationContext.getBean("jack");
            System.out.println(jack.getId());
        }
    
    }

这里我们稍许改动，因为我们只是注册了一个bean，但是我们两次取出bean的id，目的是为了测试使用java配置的时候，产生的bean是否也是单例，因为在配置文件使用了new，这里会产生一些歧义。

(4)运行结果：

0
    0

两次输出的id是一样的，说明基于Java的装配bean默认也是单例的。

完整代码的[github地址。][github]

[github]: https://github.com/louyuting/nettyRPC/tree/master/Spring/spring/spring/ch2/topic8