Spring学习（2）关于spring装配bean

港控/mmm° 2024-04-17 06:24 40阅读 0赞

### 定义一个bean ###

@Component
    public class Car implements Serializable {
        public void drive(){
            System.out.println("I'm driving this car");
        }
    }

### 定义一个组件扫描类 ###

@Configuration
    @ComponentScan
    public class CarConfig {
    }

@Configuration

从Spring3.0，@Configuration用于定义配置类，可替换xml配置文件，被注解的类内部包含有一个或多个被@Bean注解的方法，这些方法将会被AnnotationConfigApplicationContext或AnnotationConfigWebApplicationContext类进行扫描，并用于构建bean定义，初始化Spring容器。

与@Bean注解的使用：

@Configuration
    public class Config {
        public Config() {
            System.out.println("TestConfig容器初始化...");
        }
    
        @Bean(name = "getMyCar")
        public Car getCar() {
            Car c = new Car();
            c.setName("dankun");
            return c;
        }
    }

@ComponentScan 能够在Sprnig中启用组件扫描。如果没有其他配置的话, @ComponentScan默认会扫描与配置类相同的包。 Spring将会扫描这个包以及这个包下的所有子包,查找带有 @Component注解的类。使用value指定路径

@ComponentScan(value = "com.jhr")

作用类似：

<context:component-scan base-package="com.jhr.*"></context:component-scan>

扫描多个包：   @ComponentScan(basePackages = \{"com.jhr","com.oracle"\})

扫描多个类或接口：   @ComponentScan(basePackageClasses = \{Car.class,Bus.class\})

### 在测试类中加载bean ###

@RunWith(SpringRunner.class)
    @SpringBootTest
    @ContextConfiguration(classes =CarConfig.class)
    public class BeantestApplicationTests {
    
        @Autowired
        private Car car;
        @Test
        public void contextLoads() {
            car.drive();
        }
    
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xldHR1Y2Vf_size_16_color_FFFFFF_t_70][]

@ContextConfiguration  Spring整合JUnit4测试时，使用注解引入多个配置文件

加载单个文件：

@ContextConfiguration(locations="../applicationContext.xml")
    
    @ContextConfiguration(classes = SimpleConfiguration.class)

加载多个文件：

@ContextConfiguration(locations = { "classpath*:/spring1.xml", "classpath*:/spring2.xml" })

## 总结 ##

*  @Configuation等价于`<Beans></Beans>`
 *  @Bean 等价于`<Bean></Bean>`
 *  @Component 等价于`<Bean></Bean>`
 *  @ComponentScan等价于`<context:component-scan base-package="com.jhr"/>`

### 关于@Named、@Inject ###

大多数场景下可与spring注解替换

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td>Spring 注解</td> 
   <td>java 依赖注入规范</td> 
  </tr> 
  <tr> 
   <td>@Component</td> 
   <td>@Named</td> 
  </tr> 
  <tr> 
   <td>@Autowired</td> 
   <td>@Inject</td> 
  </tr> 
 </tbody> 
</table>

### 关于@Bean注解 ###

@Bean注解主要用在@Component或者@Component衍生的注解（@Configuration、@Service、@Controller等）

例如 springboot 中

1. 定义一个Configuration类，并添加bean

@Configuration
    public class CarConfiguration {
        public CarConfiguration() {
            System.out.println("CarConfiguration ***************************初始化");
        }
    
        @Bean(name = "getMyCar")
        public Car getCar() {
            Car c = new Car();
            c.setName("dankun");
            return c;
        }
    }

2. 在测试类中 使用自动装配

@Autowired
        private CarConfiguration carConfiguration;
        @Test
        public void getCarName(){
            Car car = carConfiguration.getCar();
            System.out.println("****************************");
            System.out.println(car.getName());
        }

运行结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xldHR1Y2Vf_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xldHR1Y2Vf_size_16_color_FFFFFF_t_70 2][]

详情可查看：

[https://blog.csdn.net/IPI715718/article/details/82701072][https_blog.csdn.net_IPI715718_article_details_82701072]

### 在配置中引入其他配置 ###

引用xml文件的操作方式：

<import resource="classpath*:/spring/job-timer.xml" />

引用properties 文件

<context:property-placeholder location="classpath*:properties/db.properties" />
    
    
    
    <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
            <property name="location" value="classpath*:db/jdbc.properties" />
    </bean>
    
    
    <bean id="propertyConfigure" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
            <property name="locations">
                <list>
                    <value>classpath:/opt/demo/config/demo-db.properties</value> 
                    <value>classpath:/opt/demo/config/demo-db2.properties</value> 
                </list>
            </property>
     </bean>

引用 java类的方式

@Configuration
    @Import(Car.class)
    @ImportResource("classpath:car-conf.xml")
    public class NewCar {
    }

概述：  
@Import注解是引入带有@Configuration的java类。

@ImportResource是引入spring配置文件.xml

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xldHR1Y2Vf_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/16/a82d1c9f597047a9a94d92edbd87ade1.png
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[https_blog.csdn.net_IPI715718_article_details_82701072]: https://blog.csdn.net/IPI715718/article/details/82701072