Spring装配Bean -- 通过Java代码装配Bean

港控/mmm° 2022-05-27 09:12 269阅读 0赞

接上篇[<<自动化装配Bean>>][Bean],创建对应组件如下:

## **创建可被发现的Bean:** ##

创建CD接口:

package main.java.Demo1;
    
    /**
     * @author myvina@qq.com
     * @date 18-4-15 下午6:53
     */
    
    public interface CompactDisc {
        void play();
    }

创建BeatlesCD类实现CD接口:

package main.java.Demo1;
    
    import org.springframework.stereotype.Component;
    
    /**
     * @author myvina@qq.com
     * @date 18-4-15 下午8:50
     */
    
    public class BeatlesCD implements CompactDisc {
        @Override
        public void play() {
            System.out.println("Playing Beatles");
        }
    }

创建CDPlayer类引用BeatlesCD实例:

package main.java.Demo1;  
      
    import org.springframework.beans.factory.annotation.Autowired;  
    import org.springframework.stereotype.Component;  
      
    /** 
     * @author myvina@qq.com 
     * @date 18-4-15 下午9:16 
     */  
      
    public class CDPlayer {  
        private CompactDisc cd;  
      
        public CDPlayer(CompactDisc cd){  
            this.cd = cd;  
        }  
      
        public void play(){  
            cd.play();  
        }  
    }

JavaConfig代码如下:

package main.java.Demo1;
    
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    /**
     * @author myvina@qq.com
     * @date 18-4-16 上午8:53
     */
    
    @Configuration
    public class CompactDiskConfig2 {
        @Bean
        public CompactDisc beatlesCD(){
            return new BeatlesCD();
        }
    
        @Bean
        public CDPlayer cdPlayer(){
            return new CDPlayer(beatlesCD());
        }
    }

同之前,测试代码如下:

package main.java.Demo1;
    
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.test.context.ContextConfiguration;
    import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    
    import static org.junit.Assert.assertNotNull;
    
    /**
     * @author myvina@qq.com
     * @date 18-4-15 下午6:56
     */
    
    @RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration(classes = CompactDiskConfig2.class)
    public class CDPlayerTest {
        @Autowired
        private BeatlesCD cd;
    
        @Test
        public void cdShouldNotNull(){
            assertNotNull(cd);
        }
    
        @Autowired
        private CDPlayer cdPlayer;
    
        @Test
        public void cdPlayerPlay(){
            cdPlayer.play();
        }
    }

运行cdShouldNotNull,结果如下:

四月 16, 2018 8:56:35 上午 org.springframework.test.context.support.DefaultTestContextBootstrapper getDefaultTestExecutionListenerClassNames
    信息: Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
    四月 16, 2018 8:56:36 上午 org.springframework.test.context.support.DefaultTestContextBootstrapper getTestExecutionListeners
    信息: Using TestExecutionListeners: [org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@38082d64, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@dfd3711, org.springframework.test.context.support.DirtiesContextTestExecutionListener@42d3bd8b, org.springframework.test.context.transaction.TransactionalTestExecutionListener@26ba2a48, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@5f2050f6]
    四月 16, 2018 8:56:36 上午 org.springframework.context.support.GenericApplicationContext prepareRefresh
    信息: Refreshing org.springframework.context.support.GenericApplicationContext@3a82f6ef: startup date [Mon Apr 16 08:56:36 CST 2018]; root of context hierarchy
    四月 16, 2018 8:56:38 上午 org.springframework.context.support.GenericApplicationContext doClose
    信息: Closing org.springframework.context.support.GenericApplicationContext@3a82f6ef: startup date [Mon Apr 16 08:56:36 CST 2018]; root of context hierarchy
    
    Process finished with exit code 0

运行cdPlayerPaly,结果如下:

四月 16, 2018 8:58:21 上午 org.springframework.test.context.support.DefaultTestContextBootstrapper getDefaultTestExecutionListenerClassNames
    信息: Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
    四月 16, 2018 8:58:21 上午 org.springframework.test.context.support.DefaultTestContextBootstrapper getTestExecutionListeners
    信息: Using TestExecutionListeners: [org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@38082d64, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@dfd3711, org.springframework.test.context.support.DirtiesContextTestExecutionListener@42d3bd8b, org.springframework.test.context.transaction.TransactionalTestExecutionListener@26ba2a48, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@5f2050f6]
    四月 16, 2018 8:58:22 上午 org.springframework.context.support.GenericApplicationContext prepareRefresh
    信息: Refreshing org.springframework.context.support.GenericApplicationContext@3a82f6ef: startup date [Mon Apr 16 08:58:22 CST 2018]; root of context hierarchy
    Playing Beatles
    四月 16, 2018 8:58:23 上午 org.springframework.context.support.GenericApplicationContext doClose
    信息: Closing org.springframework.context.support.GenericApplicationContext@3a82f6ef: startup date [Mon Apr 16 08:58:22 CST 2018]; root of context hierarchy
    
    Process finished with exit code 0

成功输出"Playing Beatles"(但后面多了一些关闭框架的东西,暂时不懂!),测试成功.

## **补充:** ##

1.@Bean(name="name")可以为Bean命名.

2.上面设置CDPlayer Bean时还可以用下面这种更简单的方式:

@Bean
        public CDPlayer cdPlayer(CompactDisc compactDisc){
            return new CDPlayer(compactDisc);
        }

这种方法可以不明确地引用CompactCD的@Bean方法;这种方法也是最佳的选择,因为它不会要求将CompactCD声明到同一个配置类当中,这里甚至没有要求CompactCD必须在JavaConfig中声明,实际上它可以通过组件扫描功能或自动发现或者通过XML进行配置.

3.上面是使用了CDPlayer的构造器实现了DI功能,但完全可以使用其他风格的DI配置,比如Setter方法,如下:

@Bean
        public CDPlayer cdPlayer(CompactDisc compactDisc){
            CDPlayer cdPlayer = new CDPlayer();
            cdPlayer.setCd(compactDisc);
            return cdPlayer;
        }

带有@Bean注解的方法可以采用任何必要的Java功能来产生Bean实例.

[Bean]: https://blog.csdn.net/weixin_41704428/article/details/79952985