使用@Autowired注释注入bean时的空指针异常
使用@Autowired注释注入bean时的空指针异常
提问于 2014-09-24 14:21:22
当我使用@Autowired注解将dao注入服务时，就出现了java.lang.NullPointerException，我无法修复it.Please任何人的帮助！
异常
java.lang.NullPointerException
at com.sargeras.login.service.LoginServiceImpl.register(LoginServiceImpl.java:14)服务
public class LoginServiceImpl implements LoginService{
@Autowired
private LoginDao loginDao;
public int register(UserVo userVo){
return loginDao.register(userVo);
}
}dao
@Repository
public class LoginDaoImpl extends JdbcDaoSupport implements LoginDao {
@Override
public int register(UserVo userVo) {
int result = -1;
return result;
}springmvc.xml
<context:component-scan base-package="com.sargeras" />
<mvc:annotation-driven />applicationContext.xml
<bean name="loginService" class="com.sargeras.login.service.LoginServiceImpl">
</bean>
<bean name="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" />
<property name="url" value="jdbc:oracle:thin:@localhost:1521:XE" />
<property name="username" value="sargeras" />
<property name="password" value="sargeras" />
</bean>
<bean name="loginDao" class="com.sargeras.login.repository.LoginDaoImpl">
<property name="dataSource" ref="dataSource"></property>
</bean>控制器
@Controller
@RequestMapping(value = "/login")
public class LoginController extends BaseController{
@Autowired
private LoginService service;
@RequestMapping(value = "validate")
public void toLogin(HttpServletResponse response) throws Exception {
logger.error("hhhh");
response.getWriter().print(" this is to logging 1");
}
@RequestMapping(value="register")
public void register(HttpServletRequest request,HttpServletResponse response) throws Exception{
UserVo user = new UserVo();
int result = 0;
String userName = (String)request.getParameter("usernamesignup");
String userPassword = (String)request.getParameter("passwordsignup_confirm");
String userEmail = (String)request.getParameter("emailsignup");
user.setUserName(userName);
user.setUserPassword(userPassword);
user.setUserEmail(userEmail);
result = service.register(user);
if(result == 1){
response.getWriter().print("Success");
}
}
}服务在控制器中使用，可以成功地注入。
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
id="WebApp_ID" version="2.5">
<display-name>spring_test</display-name>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:/config/applicationContext*.xml</param-value>
</context-param>
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>classpath:log4j.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>
<filter>
<filter-name>characterEncodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>characterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:/config/spring-servlet.xml</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>spring</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>**这是我的web.xml配置**
**问题解决如下：**
<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:/config/spring-servlet.xml,
classpath:/config/applicationContext*.xml
</param-value>
</init-param>
</servlet>应用程序上下文和servlet上下文不能混合，我将把它们保存在mind.Thank中。
回答 3
Stack Overflow用户
回答已采纳
发布于 2014-09-24 14:47:32
您没有发布servlet配置，但我怀疑您正在混合应用程序上下文和servlet上下文。它们是两个独立的bean容器。这里讨论的是：applicationContext not finding Controllers for Servlet context
Stack Overflow用户
发布于 2014-09-24 15:12:48
如前所述，您确实混淆了servletContext和applicationContext。要么让您的servletContext(applicationContext.xml文件)导入springmvc.xml文件，要么将mvc注释驱动的标记放在applicationContext.xml文件中。无论哪种方式，你都应该仔细阅读如何正确地构造你的上下文。
Stack Overflow用户
发布于 2014-09-24 15:20:33
如前所述，丢弃springmvc.xml并添加
<context:component-scan base-package="com.sargeras" />
<mvc:annotation-driven />敬你的applicationContext.xml。
他应该是足够的
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原文链接：
https://stackoverflow.com/questions/26019323
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