Spring(七)用@Resource和@Autowired注解完成属性装配及自动装配

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使用到注解需导入jar包：common-annotations.jar
手工装配依赖对象有两种编程方式：
一、在xml配置文件中通过bean节点进行配置，如：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsd"><bean id="personDao" class="test.spring.dao.impl.PersonDaoBean" /><bean id="personService" class="test.spring.service.impl.PersonServiceBean3"><constructor-arg index="0" type="test.spring.dao.PersonDao" ref="personDao"/><constructor-arg index="1" value="LinDL"/></bean>
</beans> 

二、在Java代码中使用@Autowired或@Resource注解方式进行装配。但需在xml配置文件中配置以下信息：

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-2.5.xsd"><!-- 把针对注解的容器注射到Spring容器中 --><context:annotation-config /><bean id="..." class="..." /></beans> 

这个配置隐式注册了多个对注释进行解析处理的处理器：AutowiredAnnotationBeanPostProcessor、CommonAnnotationBeanPostProcessor、PersistenceAnnotationBeanPostProcessor、RequireAnnotationBeanPostProcessor

在代码中使用@Autowired或@Resource注解方式进行装配，这两个注解的区别是：
@Autowired默认按类型装配，@Resource默认按名称装配，当找不到与名称匹配的bean才会按类型装配。
用于字段上
@Resource
private PersonDao personDao;
用于属性的setter方法上
@Resource
public void setPersonDao(PersonDao personDao) {
this.personDao = personDao;
}

一个应用@Resource的例子：

package test.spring.dao;public interface PersonDao {public abstract void add();}

package test.spring.dao.impl;import test.spring.dao.PersonDao;public class PersonDaoBean implements PersonDao {@Overridepublic void add(){System.out.println("执行PersonDaoBean里的test1()方法");}
}

package test.spring.service;public interface PersonService2 {public abstract void save();
}

package test.spring.service.impl;import javax.annotation.Resource;import test.spring.dao.PersonDao;
import test.spring.service.PersonService2;public class PersonServiceBean4 implements PersonService2 {// 先根据属性名personDao在beans2.xml中查找注入，如果找不到对应的就会按照类型进行注入// @Resource// private PersonDao personDao;// 也可以指定配置文件中的id进行注入// @Resource(name = "personDaoxx")private PersonDao personDao;public PersonServiceBean4() {}public PersonDao getPersonDao() {return personDao;}// 也可以通过属性的setter方法进行注入，不能用于属性的getter方法@Resourcepublic void setPersonDao(PersonDao personDao) {this.personDao = personDao;}@Overridepublic void save() {personDao.add();}
}

beans2.xml

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-2.5.xsd"><!-- 把针对注解的容器注射到Spring容器中 --><context:annotation-config /><bean id="personDaoxx" class="test.spring.dao.impl.PersonDaoBean" /><bean id="personService" class="test.spring.service.impl.PersonServiceBean4"></bean>
</beans> 

package test.spring.jnit;import org.junit.Test;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import test.spring.service.PersonService2;public class SpringTest3 {@Testpublic void testInject() {AbstractApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans2.xml");PersonService2 personService = (PersonService2) applicationContext.getBean("personService");personService.save();applicationContext.close();}}

@Autowired的应用

package test.spring.service.impl;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;import test.spring.dao.PersonDao;
import test.spring.service.PersonService2;public class PersonServiceBean5 implements PersonService2 {// 按类型进行装配// @Autowired// private PersonDao personDao;// 按名称进行装配// @Autowired@Qualifier("personDaoxx")// private PersonDao personDao;/** required=true,如果在Spring中根据类型找不到对应的容器，就会报没有成功地为这个字段注入值;* required=false,如果在Spring容器里面找不到与类型匹配的bean,就会把这个变量设为null*/@Autowired(required = true)@Qualifier("personDaoxx")private PersonDao personDao;public PersonServiceBean5() {}public PersonDao getPersonDao() {return personDao;}public void setPersonDao(PersonDao personDao) {this.personDao = personDao;}@Overridepublic void save() {personDao.add();}
}

自动装配,使用自动装配方式难以调试，程序中的bug通常在运行过程中出现问题才发现，而且容易出现难以预料的问题，故不建议使用。
beans3.xml

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-2.5.xsd"><bean id="personDaoxx" class="test.spring.dao.impl.PersonDaoBean" /><bean id="personService" class="test.spring.service.impl.PersonServiceBean6" autowire="byType"></bean></beans> 

package test.spring.service.impl;import test.spring.dao.PersonDao;
import test.spring.service.PersonService2;public class PersonServiceBean6 implements PersonService2 {private PersonDao personDao;public PersonServiceBean6() {}public void setPersonDao(PersonDao personDao) {this.personDao = personDao;}@Overridepublic void save() {personDao.add();}
}

package test.spring.jnit;import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;import test.spring.service.PersonService2;public class SpringTest5 {@Testpublic void testAutowired() {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans3.xml");PersonService2 personService = (PersonService2) applicationContext.getBean("personService");personService.save();}}

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