Spring_3

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Spring学习（8）--- @Autowired注解(一)

 

• 可以将@Autowired注解为“传统”的setter方法

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package com.mypackage;   import org.springframework.beans.factory.annotation.Autowired;   public class SimpleMovieLister {     private MovieFinder movieFinder;       @Autowired     public void setMovieFinder(MovieFinder movieFinder) {         this.movieFinder = movieFinder;     }           //..... }

•  可用于构造器或成员变量

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package com.mypackage;   import org.springframework.beans.factory.annotation.Autowired;   public class SimpleMovieLister {           @Autowired     private BeanAnnotation beanAnnotation;           private MovieFinder movieFinder;       @Autowired     public void setMovieFinder(MovieFinder movieFinder) {         this.movieFinder = movieFinder;     }           //..... }

•  默认情况下，如果因找不到合适的bean将会导致autowiring失败抛出异常，可以通过下面的方式避免

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package com.mypackage;   import org.springframework.beans.factory.annotation.Autowired;   public class SimpleMovieLister {     private MovieFinder movieFinder;       @Autowired(required=false)     public void setMovieFinder(MovieFinder movieFinder) {         this.movieFinder = movieFinder;     }           //..... }

•  每个类只能有一个构造器被标记为required=true
• @Autowired的必要属性，建议用@Required注解

 例子：

先新建两个接口（InjectionService、InjectionDAO），及实现类

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package com.mypackage;   public interface InjectionDAO {           public void save(String args); }

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package com.mypackage;   import org.springframework.stereotype.Repository;   @Repository public class InjectionDAOImpl implements InjectionDAO {       public void save(String args) {         //模拟数据库操作         System.out.println("DAO保存数据：" + args);     }   }

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package com.mypackage;   public interface InjectionService {       public void save(String args); }

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package com.mypackage;   import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service;   @Service public class InjectionServiceImpl implements InjectionService{       @Autowired     private InjectionDAO injectionDAO;       public void save(String s){         //模拟业务操作         System.out.println("Service接收参数:"+s);         s=s+":"+this.hashCode();         injectionDAO.save(s);     } }

XML配置：

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<?xml version="1.0" encoding="UTF-8"?>  <beans xmlns="http://www.springframework.org/schema/beans"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xmlns:context="http://www.springframework.org/schema/context"         xsi:schemaLocation="http://www.springframework.org/schema/beans             http://www.springframework.org/schema/beans/spring-beans-4.1.xsd             http://www.springframework.org/schema/context             http://www.springframework.org/schema/context/spring-context-4.1.xsd">                   <context:component-scan base-package="com.mypackage">         </context:component-scan>    </beans>

  单元测试：

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package com.mypackage;   import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;     public class UnitTest {           @Test     public void testAutoWired(){         ApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring-beanannotation.xml");          InjectionService service=(InjectionService)context.getBean("injectionServiceImpl");         service.save("this is autowired");;               } }

 结果：

2015-7-6 15:52:26 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@1342a80d: startup date [Mon Jul 06 15:52:26 CST 2015]; root of context hierarchy
2015-7-6 15:52:26 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [spring-beanannotation.xml]
Service接收参数:this is autowired
DAO保存数据：this is autowired:1811560891

@Autowired也可应用于构造器

修改InjectionServiceImpl实现类（添加setter）

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package com.mypackage;   import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service;   @Service public class InjectionServiceImpl implements InjectionService{           private InjectionDAO injectionDAO;           @Autowired     public void setInjectionDAO(InjectionDAO injectionDAO) {         this.injectionDAO = injectionDAO;     }       public void save(String s){         //模拟业务操作         System.out.println("Service接收参数:"+s);         s=s+":"+this.hashCode();         injectionDAO.save(s);     } }

 测试结果：

2015-7-6 15:55:23 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@939b78e: startup date [Mon Jul 06 15:55:23 CST 2015]; root of context hierarchy
2015-7-6 15:55:23 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [spring-beanannotation.xml]
Service接收参数:this is autowired
DAO保存数据：this is autowired:1860295362

 Spring学习（9）--- @Autowired注解(二)

 

• 可以使用@Autowired注解那些众所周知的解析依赖性接口，比如：BeanFactory,ApplicationContext,Environment,ResourceLoader,ApplicationEventPublisher,MessageSource

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package com.mypackage;   import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationContext;   public class MovieRecommender {       @Autowired     private ApplicationContext context;           public MovieRecommender(){     }           //... }

•  可以通过添加注解给需要该类型的数组的字段和方法，以提供ApplicationContext中的所有特定类型的bean

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private Set<MovieCatalog> movieCatalogs;   @Autowired public void setMovieCatalogs(Set<MovieCatalog> movieCatalogs) {     this.movieCatalogs = movieCatalogs; }

• 可以用于装配key为String的Map

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private Map<String , MovieCatalog>  movieCatalog;   @Autowired public void setMovieCatalog(Map<String, MovieCatalog> movieCatalog) {     this.movieCatalog = movieCatalog; }

• 如果希望数组有序，可以让bean实现org.springframework.core.Ordered接口或使用的@Order注解
• @Autowired是由Spring BeanPostProcessor处理的，所以不能在自己的BeanPostProcessor或BeanFactoryPostProcessor类型应用这些注解，这些类型必须通过XML或者Spring的@Bean注解加载

数组及Map的自动注入——例子：

　　!!!此方法也可以查看到某个接口在ioc容器里有多少个实现类的bean被加载

先定义一个BeanInterface接口

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package com.multibean;   public interface BeanInterface {   }

在定义两个实现类

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package com.multibean;   import org.springframework.stereotype.Component;   @Component public class BeanInterfaceImpl implements BeanInterface {   }

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package com.multibean;   import org.springframework.stereotype.Component;   @Component public class BeanInterface2Impl implements BeanInterface{         }

定义BeanInvoker实现数组和Map

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package com.multibean;   import java.util.*;   import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component;   @Component public class BeanInvoker {       @Autowired     private List<BeanInterface> list;           @Autowired     private Map<String,BeanInterface> map;           public void say(){         if(null != list){             System.out.println("list...");             for(BeanInterface bean:list){                 System.out.println(bean.getClass().getName());             }         }else{             System.out.println("List<BeanInterface> list is null.");         }                   if(null != map && 0 != map.size()){             System.out.println("map...");             for(Map.Entry<String,BeanInterface> entry:map.entrySet()){                 System.out.println(entry.getKey()+"-----"+entry.getValue().getClass().getName());             }         }else{             System.out.println("Map<String,BeanInterface> map is null.");         }     }       }

XML配置：

<?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-4.1.xsd">
         
        <context:component-scan base-package="com.multibean">
        </context:component-scan>   
</beans>

单元测试：

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package com.multibean;   import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;   public class UnitTest {       @Test     public void test(){         ApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring-beansnnotation.xml");         BeanInvoker beanInvoker = (BeanInvoker)context.getBean("beanInvoker");         beanInvoker.say();     } }

结果：

七月 06, 2015 10:46:41 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@32482417: startup date [Mon Jul 06 22:46:41 CST 2015]; root of context hierarchy
七月 06, 2015 10:46:41 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring-beansnnotation.xml]
list...
com.multibean.BeanInterface2Impl
com.multibean.BeanInterfaceImpl
map...
beanInterface2Impl-----com.multibean.BeanInterface2Impl
beanInterfaceImpl-----com.multibean.BeanInterfaceImpl

@Order注解----例子：

改造一下两个实现类，加上@Order注解

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package com.multibean;   import org.springframework.core.annotation.Order; import org.springframework.stereotype.Component;   @Order(value = 1) @Component public class BeanInterfaceImpl implements BeanInterface {   }

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package com.multibean;   import org.springframework.core.annotation.Order; import org.springframework.stereotype.Component;   @Order(value = 2) @Component public class BeanInterface2Impl implements BeanInterface{         }

测试同上

结果：

七月 06, 2015 10:58:58 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@1e397bcb: startup date [Mon Jul 06 22:58:58 CST 2015]; root of context hierarchy
七月 06, 2015 10:58:58 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring-beansnnotation.xml]
list...
com.multibean.BeanInterfaceImpl
com.multibean.BeanInterface2Impl
map...
beanInterface2Impl-----com.multibean.BeanInterface2Impl
beanInterfaceImpl-----com.multibean.BeanInterfaceImpl

 PS：@Order只针对数组，对于map无效

Spring学习（10）--- @Qualifier注解

 

• 按类型自动装配可能多个bean实例的情况，可以使用Spring的@Qualifier注解缩小范围（或指定唯一），也可以指定单独的构造器参数或方法参数
• 可用于注解集合类型变量

例子：

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package com.mypackage;   import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier;   public class MovieRecommender {       @Autowired     @Qualifier("main")     private MovieCatalog movieCatalog;       }

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package com.mypackage;   import org.springframework.beans.factory.annotation.Qualifier;   public class MovieRecommender {       private MovieCatalog movieCatalog;       public void prepare(@Qualifier("main")MovieCatalog movieCatalog){         this.movieCatalog=movieCatalog;     }       }

PS：应用于构造器的方法比较常用

• XML文件中使用qualifier:

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<?xml version="1.0" encoding="UTF-8"?>  <beans xmlns="http://www.springframework.org/schema/beans"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xmlns:context="http://www.springframework.org/schema/context"         xsi:schemaLocation="http://www.springframework.org/schema/beans             http://www.springframework.org/schema/beans/spring-beans-4.1.xsd             http://www.springframework.org/schema/context             http://www.springframework.org/schema/context/spring-context-4.1.xsd">                    <context:component-scan base-package="com.multibean">         </context:component-scan>                     <bean class="com.mypackage.MovieCatalog">             <qualifier value="main"></qualifier>         </bean>                   <bean class="com.mypackage.MovieCatalog">             <qualifier value="action"></qualifier>         </bean> </beans>

• 如果通过名字进行注解注入，主要使用的不是@Autowired(即使在技术上能够通过@Qualifier指定bean的名称)，替代方式是使用JSR-250@Resource注解，它通过其独特的名称来定义来识别特定的目标（这是一个与所声明的类型是无关的匹配过程）
• 因语义差异，集合或Map类型的bean无法通过@Autowired来注入，因为没有类型匹配到这样的bean，为这些bean使用@Resource注解，通过唯一名称引用集合或Map的bean
• @Autowired适用于fields，constructors，multi-argument method这些允许在参数级别使用@Qualifier注解缩小范围的情况
• @Resource适用于成员变量，只有一个参数的setter方法，所以在目标是构造器或者一个多参数方法时，最好的方式是使用@Qualifier

例子：

先定义一个BeanInterface接口

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package com.multibean;   public interface BeanInterface {   }

在定义两个实现类

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package com.multibean;   import org.springframework.stereotype.Component;   @Component public class BeanInterfaceImpl implements BeanInterface {   }

　　

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package com.multibean;   import org.springframework.stereotype.Component;   @Component public class BeanInterface2Impl implements BeanInterface {   }

定义BeanInvoker实现@Qualifier指定bean

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package com.multibean;     import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.stereotype.Component;   @Component public class BeanInvoker {       @Autowired     @Qualifier("beanInterfaceImpl")     private BeanInterface beanInterface;           public void say(){                   if(null != beanInterface){             System.out.println(beanInterface.getClass().getName());         }else{             System.out.println("BeanInterface is null.");         }               }       }

单元测试：

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package com.multibean;   import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;   public class UnitTest {       @Test     public void test(){         ApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring-beansnnotation.xml");         BeanInvoker beanInvoker = (BeanInvoker)context.getBean("beanInvoker");         beanInvoker.say();     } }

结果：

七月 06, 2015 11:41:38 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@1e397bcb: startup date [Mon Jul 06 23:41:38 CST 2015]; root of context hierarchy
七月 06, 2015 11:41:38 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring-beansnnotation.xml]
com.multibean.BeanInterfaceImpl

修改BeanInvoker

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package com.multibean;     import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.stereotype.Component;   @Component public class BeanInvoker {       @Autowired     @Qualifier("beanInterface2Impl")     private BeanInterface beanInterface;           public void say(){                   if(null != beanInterface){             System.out.println(beanInterface.getClass().getName());         }else{             System.out.println("BeanInterface is null.");         }               }       }

结果：

七月 06, 2015 11:43:38 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@1e397bcb: startup date [Mon Jul 06 23:43:38 CST 2015]; root of context hierarchy
七月 06, 2015 11:43:38 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring-beansnnotation.xml]
com.multibean.BeanInterface2Impl