Spring学习笔记（四）

1、注解注入

注解注入顾名思义就是通过注解来实现注入。

Spring和注入相关的常见注解有Autowired、Resource、Qualifier。

Autowired，按类型装配。Resource，按名称装配，当找不到与名称匹配的bean才会按类型装配。Qualifier和Autowired配合使用，指定bean的名称。

Autowired和Resource注解可以标注在属性或属性的Set方法上。

为了让系统能够识别相应的注解，需要在配置文件中配置注册对注解进行解析处理的处理器。使用@Autowired注解，必须事先在Spring容器中声明AutowiredAnnotationBeanPostProcessor的Bean。使用@Resource、@PostConstruct、@PreDestroy等注解，必须事先在Spring容器中声明CommonAnnotationBeanPostProcessor的Bean。Spring为我们提供了简化配置方式，<context:annotation-config/>，自动完成声明。

2、实例

（1）PersonDao.java

public interface PersonDao { public void add(); }

（2）PersonDaoBean.java

public class PersonDaoBean implements PersonDao { public void add() { System.out.println("PersonDaoBean add"); } }

（3）PersonService.java

public interface PersonService { public void save(); }

（4）PersonServiceBean1.java

public class PersonServiceBean1 implements PersonService { @Autowired private PersonDao personDao; public PersonServiceBean1() {} public PersonServiceBean1(PersonDao personDao) { this.personDao = personDao; } public void save(){ personDao.add(); } }

（5）PersonServiceBean2.java

public class PersonServiceBean2 implements PersonService { private PersonDao personDao; @Autowired public void setPersonDao(PersonDao personDao) { this.personDao = personDao; } public PersonServiceBean2() {} public PersonServiceBean2(PersonDao personDao) { this.personDao = personDao; } public void save(){ personDao.add(); } }

（6）PersonServiceBean3.java

public class PersonServiceBean3 implements PersonService { /** * @Autowired(required=true)表示必须为personDao注入值 * @Qualifier("personDao")指定注入name为personDao的bean，如果不存在则异常 */ @Autowired(required=true) @Qualifier("personDao") private PersonDao personDao; public PersonServiceBean3() {} public PersonServiceBean3(PersonDao personDao) { this.personDao = personDao; } public void save(){ personDao.add(); } }

（7）PersonServiceBean4.java

public class PersonServiceBean4 implements PersonService { @Resource private PersonDao personDao; public PersonServiceBean4() {} public PersonServiceBean4(PersonDao personDao) { this.personDao = personDao; } public void save(){ personDao.add(); } }

（8）PersonServiceBean5.java

public class PersonServiceBean5 implements PersonService { /** * @Resource(name="personDao")指定注入name为personDao的bean，如果不存在则异常 */ @Resource(name="personDao") private PersonDao personDao; public PersonServiceBean5() {} public PersonServiceBean5(PersonDao personDao) { this.personDao = personDao; } public void save(){ personDao.add(); } }

（9）PersonServiceBean6.java

public class PersonServiceBean6 implements PersonService { private PersonDao personDao; @Resource public void setPersonDao(PersonDao personDao) { this.personDao = personDao; } public PersonServiceBean6() {} public PersonServiceBean6(PersonDao personDao) { this.personDao = personDao; } public void save(){ personDao.add(); } }

（10）beans.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/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd"> <!-- 使用<context:annotation-config/>隐式地向 Spring容器注册BeanPostProcessor --> <context:annotation-config/> <!-- 使用@Autowired注解，必须事先在Spring容器中声明AutowiredAnnotationBeanPostProcessor的Bean --> <!-- <bean class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" /> --> <!-- 使用@Resource、@PostConstruct、@PreDestroy等注解，必须事先在Spring容器中声明CommonAnnotationBeanPostProcessor的Bean --> <!-- <bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" /> --> <bean id="personDao" class="com.spring.dao.impl.PersonDaoBean"></bean> <bean id="personService1" class="com.spring.service.impl.PersonServiceBean1"></bean> <bean id="personService2" class="com.spring.service.impl.PersonServiceBean2"></bean> <bean id="personService3" class="com.spring.service.impl.PersonServiceBean3"></bean> <bean id="personService4" class="com.spring.service.impl.PersonServiceBean4"></bean> <bean id="personService5" class="com.spring.service.impl.PersonServiceBean5"></bean> <bean id="personService6" class="com.spring.service.impl.PersonServiceBean6"></bean> </beans>

（11）Test.java

public class Test { @org.junit.Test public void test1() { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); PersonService personService = (PersonService)ctx.getBean("personService1"); personService.save(); } @org.junit.Test public void test2() { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); PersonService personService = (PersonService)ctx.getBean("personService2"); personService.save(); } @org.junit.Test public void test3() { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); PersonService personService = (PersonService)ctx.getBean("personService3"); personService.save(); } @org.junit.Test public void test4() { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); PersonService personService = (PersonService)ctx.getBean("personService4"); personService.save(); } @org.junit.Test public void test5() { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); PersonService personService = (PersonService)ctx.getBean("personService5"); personService.save(); } @org.junit.Test public void test6() { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); PersonService personService = (PersonService)ctx.getBean("personService6"); personService.save(); } }

3、结果

test1()运行结果：

PersonDaoBean add

test2()运行结果：

PersonDaoBean add

test3()运行结果：

PersonDaoBean add

test4()运行结果：

PersonDaoBean add

test5()运行结果：

PersonDaoBean add

test6()运行结果：

PersonDaoBean add