@ ManagedBean中的NPE-javax.servlet.ServletException：执行资源注入时发生错误

问题描述 投票：0回答：1

我有Spring项目，现在我想添加几个JSF（Primefaces）xhtml页面，但是当我尝试从现有服务获取数据时，在@PostConstruct方法上的@ManagedBean中出现空指针异常？

您知道如何正确地将AuctionViewService导入到我的@ManagedBean吗？我认为这是问题所在，但我不知道如何解决：）

在Java类下面，有带空指针的stacktrace（我也在SalesBean.java中用NPE标记行）

这是我的xhtml页面：

<?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://xmlns.jcp.org/jsf/html"
      xmlns:p="http://primefaces.org/ui">
<h:head>
    <link rel="stylesheet" href="${pageContext.request.contextPath}/css/bootstrap.min.css"></link>
    <link rel="stylesheet" href="${pageContext.request.contextPath}/css/main.css"></link>
    <script src="${pageContext.request.contextPath}/js/jquery-3.4.1.min.js" type=""></script>
    <script src="${pageContext.request.contextPath}/js/bootstrap.min.js" type=""></script>
    <script type="text/javascript" src="${pageContext.request.contextPath}/js/common/main.js"></script>

    <title>Sales</title>

</h:head>
<h:body>
<div id="wrapper">

    <div id="navigationMenuPlaceholder"></div>

    <!-- Page Content -->
    <div id="page-content-wrapper">
        <div class="container-fluid">
            <div class="row">
                <div class="col-lg-12">
                    <p:panelGrid columns="2">
                        <h:outputText value="#{SalesBean.firstName}"/>
                        <h:outputText value="#{SalesBean.lastName}" />
                    </p:panelGrid>

                    <p:dataTable var="property" value="#{SalesBean.userProperty}">
                        <p:column headerText="PropertyId">
                            <h:outputText value="#{property.propertyId}" />
                        </p:column>

                        <p:column headerText="UserId">
                            <h:outputText value="#{property.userId}" />
                        </p:column>

                        <p:column headerText="Street">
                            <h:outputText value="#{property.street}" />
                        </p:column>

                        <p:column headerText="House no">
                            <h:outputText value="#{property.homeNumber}" />
                        </p:column>

                        <p:column headerText="Local no">
                            <h:outputText value="#{property.localNumber}" />
                        </p:column>

                        <p:column headerText="Post code">
                            <h:outputText value="#{property.postCode}" />
                        </p:column>

                        <p:column headerText="City">
                            <h:outputText value="#{property.city}" />
                        </p:column>

                        <p:column headerText="Price">
                            <h:outputText value="#{property.price}" />
                        </p:column>

                        <p:column headerText="Size">
                            <h:outputText value="#{property.size}" />
                        </p:column>

                    </p:dataTable>
                </div>
            </div>
        </div>
    </div>
    <div id="footerPlaceholder">
    </div>
    <!-- /#page-content-wrapper -->

</div>
</h:body>
</html>

SalesBean：

package application.beans;

import application.model.views.AuctionView;
import application.service.AuctionViewService;
import lombok.Getter;
import lombok.Setter;
import javax.annotation.PostConstruct;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ManagedProperty;
import javax.faces.bean.ViewScoped;
import java.util.ArrayList;
import java.util.List;

@Setter
@Getter
@ViewScoped
@ManagedBean(name="SalesBean")
public class SalesBean {

    @ManagedProperty("#{auctionViewService}")
    private AuctionViewService auctionViewService;

    //private String userName =  SecurityContextHolder.getContext().getAuthentication().getName();
    private String userName =  "[email protected]";
    private String firstName = "first";
    private String lastName = "last";
    private List<AuctionView> userProperty = new ArrayList<>();

    @PostConstruct
    public void init() { userProperty = auctionViewService.findByEmail(userName); //NULL POINTER EXCEPTION in this line
    }
}

AuctionViewServiceImpl：

package application.service;

import application.dao.*;
import application.model.views.AuctionView;
import org.apache.log4j.Logger;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import java.util.List;

@Service("auctionViewService")
public class AuctionViewServiceImpl implements AuctionViewService {

    final static Logger LOGGER = Logger.getLogger(AuctionViewServiceImpl.class.getName());
    private final AuctionViewDAO auctionViewDAO;

    public AuctionViewServiceImpl(AuctionViewDAO auctionViewDAO) {
        this.auctionViewDAO = auctionViewDAO;
    }

    @Override
    public List<AuctionView> findAll() {
        return auctionViewDAO.findAll();
    }

    @Override
    public ResponseEntity<Object> findByType(String propertyType) {
        return new ResponseEntity<>(auctionViewDAO.findByType(propertyType), HttpStatus.OK);
    }

    @Override
    public List<AuctionView> findByEmail(String email) {
        return auctionViewDAO.findByEmail(email);
    }
}

faces-config.xml：

<?xml version="1.0" encoding="UTF-8"?>
<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_1.xsd"
              version="2.1">

    <application>
        <el-resolver>
            org.springframework.web.jsf.el.SpringBeanFacesELResolver
        </el-resolver>
    </application>

</faces-config>

web.xml

<web-app  version="2.4"
         xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <display-name>khn</display-name>


    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
    </welcome-file-list>

    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:/applicationContext.xml</param-value>
    </context-param>

    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>WEB-INF/servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    <filter>
        <filter-name>springSecurityFilterChain</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>springSecurityFilterChain</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

stacktrace：https://pastebin.com/iaBHUupQ如果需要，我可以附加更多文件和整个项目结构，但是问题是将AuctionViewService导入SalesBean，或者可能是混合JSF和Spring注释

spring jsf primefaces managed-bean
1个回答
0
投票

好吧，我将@ManagedBean批注更改为@Component，将AuctionViewService与@Autowire链接起来，它对我有用:)，但是如何解释这种情况？

package application.beans;

import application.model.views.AuctionView;
import application.service.AuctionViewService;
import lombok.Getter;
import lombok.Setter;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.stereotype.Component;
import javax.annotation.PostConstruct;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

@Setter
@Getter
@ViewScoped
@Component
//@ManagedBean(name="SalesBean")
public class SalesBean implements Serializable {

    @Autowired
    private  AuctionViewService auctionViewService;

    //private String userName =  SecurityContextHolder.getContext().getAuthentication().getName();
    private String userName =  "[email protected]";
    private String firstName = "first";
    private String lastName = "last";
    private List<AuctionView> userProperty = new ArrayList<>();


    @PostConstruct
    public void init() { userProperty = auctionViewService.findByEmail(userName);
    }
}
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