Spring学习(十九)-自动装配

墨蓝 2024-02-19 16:06 17阅读 0赞

自动装配：
        Spring利用依赖注入（DI），完成对IOC容器中中各个组件的依赖关系赋值；
    
    @Autowired：自动注入，可以用在构造器，参数，方法，属性；都是从容器中获取参数组件的值
         1）、[标注在方法位置]：@Bean+方法参数；参数从容器中获取;默认不写@Autowired效果是一样的；都能自动装配
         2）、[标在构造器上]：如果组件只有一个有参构造器，这个有参构造器的@Autowired可以省略，参数位置的组件还是可以自动从容器中获取
         3）、放在参数位置：

@Autowired -----》AutowiredAnnotationBeanPostProcessor:解析完成自动装配功能；

@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD, ElementType.ANNOTATION_TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface Autowired {
    
    	/**
    	 * 设置是否需要 默认是true
    	 * <p>Defaults to {@code true}.
    	 */
    	boolean required() default true;
    
    }

@Component
    public class Car {
    
    	public Car(){
    		System.out.println("car constructor...");
    	}
    
    	public void init(){
    		System.out.println("car ... init...");
    	}
    
    	public void detory(){
    		System.out.println("car ... detory...");
    	}
    
    }
    
    @Component
    public class Boss {
    	
    	private Car car;
    
    	//构造器要用的组件，都是从容器中获取
    	public Boss(Car car){
    		this.car = car;
    		System.out.println("Boss...有参构造器");
    	}
    	public Car getCar() {
    		return car;
    	}
    	//@Autowired
    	//标注在方法，Spring容器创建当前对象，就会调用方法，完成赋值；
    	//方法使用的参数，自定义类型的值从ioc容器中获取
    	public void setCar(Car car) {
    		this.car = car;
    	}
    	@Override
    	public String toString() {
    		return "Boss [car=" + car + "]";
    	}
    }

`@Qualifier：使用@Qualifier指定需要装配的组件的id，而不是使用属性名`

@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.TYPE, ElementType.ANNOTATION_TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Inherited
    @Documented
    public @interface Qualifier {
    
    	String value() default "";
    
    }

@Primary：让Spring进行自动装配的时候，默认使用首选的bean

@Target({ElementType.TYPE, ElementType.METHOD})
    @Retention(RetentionPolicy.RUNTIME)
    @Inherited
    @Documented
    public @interface Primary {
    
    }

@Resource(JSR250):java规范
           可以和@Autowired一样实现自动装配功能；默认是按照组件名称进行装配的；
           没有能支持@Primary功能没有支持@Autowired（reqiured=false）;

@Target({TYPE, FIELD, METHOD})
    @Retention(RUNTIME)
    public @interface Resource {
        
       //装配的名称
        String name() default "";
    
        String lookup() default "";
        //装配的类型
        Class<?> type() default java.lang.Object.class;
    
        
        enum AuthenticationType {
                CONTAINER,
                APPLICATION
        }
    
       
        AuthenticationType authenticationType() default AuthenticationType.CONTAINER;
    
        
        boolean shareable() default true;
    
       
        String mappedName() default "";
    
        
        String description() default "";
    }

@Inject(JSR330)[java规范的注解]：
       
          需要导入javax.inject的包，和Autowired的功能一样。没有required=false的功能；

@Target({ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.FIELD})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface Inject {
    }

测试：

@Controller
    public class BookController {
    
    	@Autowired
    	private BookService bookService;
    
    }
    
    @Service
    public class BookService {
    
    	@Autowired(required=false)
    	private BookDao bookDao;
    
    	public void print(){
    		System.out.println(bookDao);
    	}
    
    	@Override
    	public String toString() {
    		return "BookService [bookDao=" + bookDao + "]";
    	}
    
    }
    //名字默认是类名首字母小写
    @Repository
    public class BookDao {
    
    	private String lable = "1";
    
    	public String getLable() {
    		return lable;
    	}
    
    	public void setLable(String lable) {
    		this.lable = lable;
    	}
    
    	@Override
    	public String toString() {
    		return "BookDao [lable=" + lable + "]";
    	}
    
    }

配置类：

@Configuration
    @ComponentScan({"com.spring"})
    public class MainConifgOfAutowired {
    }

测试类：

@Test
    	public void test01(){
    		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConifgOfAutowired.class);
    
    		BookService bookService = applicationContext.getBean(BookService.class);
    		System.out.println(bookService);
    
    		
    		applicationContext.close();
    	}

结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70][]

修改配置测试@primary:

@Configuration
    @ComponentScan({"com.spring"})
    public class MainConifgOfAutowired {
    
    	@Primary
    	@Bean("bookDao2")
    	public BookDao bookDao(){
    		BookDao bookDao = new BookDao();
    		bookDao.setLable("2");
    		return bookDao;
    	}
    
    }

如果找到多个相同类型的组件，再将属性的名称作为组件的id去容器中查applicationContext.getBean("bookDao")。

@Primary：让Spring进行自动装配的时候，默认使用首选的bean；

测试结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 1][]

@Qualifier("bookDao")：使用@Qualifier指定需要装配的组件的id，而不是使用属性名

修改service：

@Service
    public class BookService {
    
        @Qualifier("bookDao")
    	@Autowired(required=false)
    	private BookDao bookDao;
    
    	public void print(){
    		System.out.println(bookDao);
    	}
    
    	@Override
    	public String toString() {
    		return "BookService [bookDao=" + bookDao + "]";
    	}
    
    }

结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 2][]

注意：如果指定了@Qualifier但是@Primary虽然是首选的bean，其结果是@Qualifier决定注入的是那个bean对象。

@Resource：

修改service:

@Service
    public class BookService {
    
        @Resource(name="bookDao2")
    	private BookDao bookDao;
    
    	@Override
    	public String toString() {
    		return "BookService [bookDao=" + bookDao + "]";
    	}
    
    }

结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 3][]

@Inject:  需要导入javax.inject的包，和Autowired的功能一样。没有required=false的功能；

pom:

<dependency>
                <groupId>javax.inject</groupId>
                <artifactId>javax.inject</artifactId>
                <version>1</version>
            </dependency>

修改service:

@Service
    public class BookService {
    
        @Inject
    	private BookDao bookDao;
    
    	@Override
    	public String toString() {
    		return "BookService [bookDao=" + bookDao + "]";
    	}
    
    }

结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 4][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/2c21c8e6ce93434ba861825f6a50d495.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/f5a4051c76ca4965824ca2aa44c6a9f8.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 2]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/3523126d06c84235b28df92a99980aeb.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 3]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/dbd013f597294f32b3864dea12e9e3b9.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 4]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/00671e257db64800ad4c414ff1da29d7.png