将 Spring 服务 bean 注入 JSF ManagedBean 时出现 NullPointerException

Question

Tomcat 7、JSF 2、Spring 3、Java 6

Error: NullPointerException on userService.checkUser(getLogin()) (userService is null) in UserBean.java 访问jsf页面时。

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
          http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
           version="2.5">

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <listener>
        <listener-class>org.springframework.web.context.request.RequestContextListener</listener-class>
    </listener>

    <servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>*.jsf</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>/faces/*</url-pattern>
    </servlet-mapping>
</web-app>

faces-config.xml

<faces-config xmlns="http://java.sun.com/xml/ns/javaee"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd"
              version="2.0">
    <application>
       <el-resolver>org.springframework.web.jsf.el.SpringBeanFacesELResolver</el-resolver>
        <resource-bundle>
            <base-name>i18n</base-name>
            <var>msg</var>
        </resource-bundle>
        <locale-config>
            <default-locale>en</default-locale>
            <supported-locale>ru</supported-locale>
        </locale-config>
    </application>
</faces-config>

applicationContext.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:tx="http://www.springframework.org/schema/tx"
       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/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!-- Services Beans -->
    <bean id="userService" class="service.UserServiceImpl">
        <property name="userDao" ref="userDao"/>
    </bean>

    <!-- DAOs -->
    <bean id="userDao" class="dao.UserDaoImpl">
        <property name="sessionFactory" ref="sessionFactory"/>
    </bean>

    <!-- Hibernate session factory -->
    <bean id="sessionFactory"
          class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="configLocation">
            <value>classpath:/hibernate.cfg.xml</value>
        </property>
    </bean>

    <tx:annotation-driven/>
    <bean id="transactionManager"
          class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory"/>
    </bean>
</beans>

UsersBean.java

package beans;

import service.UserService;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.ManagedProperty;
import javax.faces.bean.SessionScoped;
import java.io.Serializable;

@ManagedBean(name="usersBean")
@SessionScoped
public class UsersBean implements Serializable{
    private String login;
    private String password;
    @ManagedProperty(name = "userService", value = "#{userService}")
    private UserService userService;

    ...Getters, setters for every field...

    public void checkRegistred(){
        userService.checkUser(getLogin());
    }
}

xhtml 文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html
        PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:ui="http://java.sun.com/jsf/facelets">

<h:head>
    <title>Simple JSF Facelets page</title>
</h:head>

<h:body>
    <ui:composition template="layout.xhtml">
        <ui:define name="content">
            <h:link value="First page" outcome="index.xhtml"></h:link>
            <br/>
            <h:link value="Third page" outcome="third.xhtml"></h:link>
            <br/>
            Hello #{usersBean.login} with pass #{usersBean.password}
            <br/>
            You are #{usersBean.checkRegistred()}
        </ui:define>
    </ui:composition>
</h:body>

</html>

Answer 1

查看this question 及其答案。在您的情况下，当您使用 XML 配置时，为了使用 @autowired 注释，您还需要修改您的 userServide 声明如下：

<bean id="userService" class="service.UserServiceImpl" autowire-candidate="true">
    <property name="userDao" ref="userDao"/>
</bean>

autowire-candidate 属性设置为 true，userService 将可用于自动连线。

更新：

package beans;

import ...

@SessionScoped
public class UsersBean implements Serializable {

    private String login;

    private String password;

    @Autowired
    private UserService userService;

    ...Getters, setters for every field...

    public void checkRegistred(){
        userService.checkUser(getLogin());
    }

}

此外，它应该在您的 XML 中找到：

<context:component-scan base-package="beans.*" />
<context:annotation-config />