Spring2.5繼續堅持了這個發展趨向，特別是為那些使用Java 5或更新版本java的開發人員提供了進一步簡化而強大的新特性。這些新特性包括：注解驅動的依賴性注入（annotation-driven dependency injection），使用注解而非XML元數據來自動偵測classpath上的Spring組件，注解對生命周期方法的支持，一個新的web控制器模型將請求映射到加注解的方法上，在測試框架中支持Junit4，Spring XML命名空間的新增內容，等等。
項目中使用的spring2.5版本。如果想要使用spring提供的注解功能.
applicationContext.xml配置文件中增加如下配置:
<?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-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
<!-- Using annontations -->
<context:annotation-config></context:annotation-config>
新增以下三項才可以使用注解功能
xmlns:context="http://www.springframework.org/schema/context"
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
<context:annotation-config></context:annotation-config>
或者<bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor"/> 注冊一個單獨的Spring post-processor.
一個沒有實現任何接口的業務類，配置如下:
public class LogService extends Service{
public LogBiz(){}
@Resource //默認按名稱查找bean. 如果找不到，則按類型匹配bean.
private BaseDao dao;
}
tomcat啟動錯誤1：
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'logBiz': Injection of resource fields failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [com.ccms.base.dao.BaseDAO] is defined: expected single matching bean but found 40: [baseDAO, loginDAO, logDAO]
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessAfterInstantiation(CommonAnnotationBeanPostProcessor.java:291)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:876)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:437)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:383)
at java.security.AccessController.doPrivileged(Native Method)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:353)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:245)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:169)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:242)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:269)
... 32 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [com.ccms.base.dao.BaseDAO] is defined: expected single matching bean but found 40: [baseDAO, loginDAO, logDAO]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:583)
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:418)
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:497)
at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:145)
at org.springframework.beans.factory.annotation.InjectionMetadata.injectFields(InjectionMetadata.java:79)
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessAfterInstantiation(CommonAnnotationBeanPostProcessor.java:288)
... 42 more
使用@Resource默認按名稱查找bean. 如果找不到，則按類型匹配bean.而名稱dao沒有找到，所以會根據BaseDAO匹配，但是BaseDAO是一個接口：
<bean id="loginDAO" class="com.test.dao.loginDAO" parent="baseDAO" />
<bean id="logDAO" class="com.test.dao.logDAO" parent="baseDAO" />
<bean id="baseDAO" class="com.ccms.base.dao.BaseDAOImpl">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
<property name="simpleJdbcTemplate">
<ref bean="simpleJdbcTemplate" />
</property>
</bean>
有兩個實現了BaseDAO接口的類，所以spring就不知道應該使用哪一個了。直接拋出異常。
解決方法1：
我們可以看到baseDAO名稱是唯一的， 所以如果想要按照名稱匹配，則直接寫baseDAO就可以了
@Resource
private BaseDAO baseDAO;
解決方法2：
@Autowired //默認按照類型匹配，同樣應為有兩個子類bean，所以拋出異常。
@Qualifier("loginDAO") //限定bean
private BaseDAO dao;
參考博客：
http://doc.chinaunix.net/java/200801/240056.shtml
http://stackoverflow.com/questions/10534053/autowiring-two-beans-implementing-same-interface-how-to-set-default-bean-to-au
posted on 2013-03-21 10:22
David1228 閱讀(2503)
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