Question

我刚刚阅读了本文（http://www.infoq.com/articles/spring-2.5-part-1）中的@Resource注释，并希望在Tomcat 6.0.26和Spring 3.0.3上使用它

但它不起作用 - ds类中的字段Users未初始化，当我尝试进行查询时，我有NullPointerException。

档案src/org/example/db/Users.java

package org.example.db;
import javax.sql.DataSource;
import javax.annotation.Resource;

@Repository
public class Users {

 @Resource private DataSource ds;
 ...
}

档案WEB-INF/spring-servlet.xml

<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:jee="http://www.springframework.org/schema/jee"
 xmlns:context="http://www.springframework.org/schema/context"
 xsi:schemaLocation="http://www.springframework.org/schema/beans
 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
 http://www.springframework.org/schema/jee
 http://www.springframework.org/schema/jee/spring-jee-2.0.xsd
 http://www.springframework.org/schema/context
 http://www.springframework.org/schema/context/spring-context-3.0.xsd">

 <context:component-scan base-package="org.example.web.controller,org.example.db" />

 <bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor">
  <property name="alwaysUseJndiLookup" value="true" />
 </bean>

 <jee:jndi-lookup id="ds" jndi-name="java:comp/env/jdbc/mydb" />

</beans>

档案WEB-INF/web.xml

 <resource-ref>
  <description>DB Connection</description>
  <res-ref-name>jdbc/mydb</res-ref-name>
  <res-type>javax.sql.DataSource</res-type>
  <res-auth>Container</res-auth>
 </resource-ref>

在日志文件中：

DEBUG 2010-09-27 21:56:00,085: Creating shared instance of singleton bean 'ds'
DEBUG 2010-09-27 21:56:00,085: Creating instance of bean 'ds'
DEBUG 2010-09-27 21:56:00,086: Eagerly caching bean 'ds' to allow for resolving potential circular references
DEBUG 2010-09-27 21:56:00,106: Invoking afterPropertiesSet() on bean with name 'ds'
DEBUG 2010-09-27 21:56:00,116: Finished creating instance of bean 'ds'
DEBUG 2010-09-27 21:56:00,149: Found injected element on class [org.example.db.Users]: ResourceElement for private javax.sql.DataSource org.example.db.Users.ds
DEBUG 2010-09-27 21:56:00,152: Found injected element on class [org.example.db.Users]: ResourceElement for private javax.sql.DataSource org.example.db.Users.ds
DEBUG 2010-09-27 21:56:00,161: Processing injected method of bean 'users': ResourceElement for private javax.sql.DataSource org.example.db.Users.ds
DEBUG 2010-09-27 21:56:00,163: Returning cached instance of singleton bean 'ds'
DEBUG 2010-09-27 21:56:00,442: Returning cached instance of singleton bean 'ds'
DEBUG 2010-09-27 21:56:00,593: Rejected bean name 'ds': no URL paths identified
DEBUG 2010-09-27 21:56:00,738: Rejected bean name 'ds': no URL paths identified

我不知道为什么它不起作用。我在documentation找到了这个：

注意：默认的CommonAnnotationBeanPostProcessor将由“context：annotation-config”和“context：component-scan”XML标记注册。如果要指定自定义CommonAnnotationBeanPostProcessor bean定义，请删除或关闭默认注释配置！

我认为这可能与我的问题有关，但在这种情况下我不知道如何“删除或关闭默认的注释配置”。

请帮忙。提前谢谢！

Answer 1

现在这个问题已经解决了。

所有这些代码都有效，但我认为问题出在一些相关的类中。例如，我有以下自动装配层次结构：dataSource注入到Users类，Users类注入Validator，Validator从Controller调用。在这个链中有一些错误：

使用新的Validator实例创建用户
在@Autowiring传播之后，用户没有注入Validator，因为这个类在另一个包中，而组件扫描找不到它
以后用户没有注入Validator，因为此类没有@Component注释
Controller使用默认构造函数

解决所有这些问题后，一切正常。

DataSource未使用alwaysUseJndiLookup设置注入@Resource注释字段

1 个答案: