@Autowired 导致 NullPointerException

【问题标题】：@Autowired results in NullPointerException@Autowired 导致 NullPointerException
【发布时间】：2024-04-29 09:45:02
【问题描述】：

我有一个 Facelets/JSF Managed Beans/Hibernate 应用程序。现在我正在尝试通过注释在我的 bean 中实现 DI。我有 2 个：LoginBean、RegistrationBean（每个负责相应的页面）。问题是，每当我尝试在 RegistrationBean 中自动装配属性时，我都会得到 NPE。但是，如果我将相同的类字段放入 LoginBean - 它们是自动装配的，没有问题！下面是我的 ManagedBeans、applicationContext.xml（数据库设置没问题，所以我不会发布 db.properties）和一个我正在尝试自动装配的类 Stacktrace。

致以最诚挚的问候。

纳扎尔

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.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <context:component-scan base-package="com.dataart.mediaportal"/>

    <!-- DATA SOURCE AND PERSISTENCE SETTINGS-->
    <bean id="propertiesPlaceholderConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>classpath:db.properties</value>
            </list>
        </property>
    </bean>

    <bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="dmDataSource"/>
        <property name="packagesToScan" value="com.dataart.mediaportal"/>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">${db.dialect}</prop>
                <prop key="hibernate.show_sql">${db.show_sql}</prop>
                <prop key="hibernate.hbm2ddl.import_files">${db.import_files}</prop>
                <prop key="hibernate.hbm2ddl.auto">${db.hbm2ddl_auto}</prop>
                <prop key="connection.pool_size">${db.pool_size}</prop>
                <prop key="current_session_context_class">${db.current_session_context_class}</prop>
                <!--<prop key="hibernate.cache.provider_class">${db.provider_class}</prop>-->
                <!--<prop key="hibernate.cache.use_second_level_cache">${db.use_second_level_cache}</prop>-->
                <!--<prop key="hibernate.cache.use_query_cache">${db.use_query_cache}</prop>-->
            </props>
        </property>
    </bean>

    <bean id="transactionManager"
        class="org.springframework.orm.hibernate3.HibernateTransactionManager">
        <property name="dataSource" ref="dmDataSource" />
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>

    <bean id="dmDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="${db.driver}" />
        <property name="url" value="${db.url}" />
        <property name="username" value="${db.username}" />
        <property name="password" value="${db.password}" />
        <property name="maxWait" value="5000" />
        <property name="maxActive" value="5" />
    </bean>

</beans>

登录豆：

package com.dataart.mediaportal.controller.bean;

import com.dataart.mediaportal.dao.impl.UserDAOImpl;
import com.dataart.mediaportal.model.User;
import java.io.IOException;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
import javax.faces.context.ExternalContext;
import javax.faces.context.FacesContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
@RequestScoped
@ManagedBean(name = "loginBean")
public class LoginBean extends BaseBean {

    private static final Logger logger = LoggerFactory.getLogger(LoginBean.class);
    private User user;
    private String login;
    private String password;
    @Autowired
    private UserDAOImpl userDAO;

    public String getLogin() {
        return login;
    }

    public void setLogin(String login) {
        this.login = login;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }


    public String authorize() {
        logger.debug("Searching user in database...");
        user = userDAO.login(login, password);
        if (user != null) {
            logger.debug("User found.");
            getSession(false).setAttribute("user", user);
            return "login";
        }
        logger.warn("User has not been found. Login: " + login + ", Password: " + password);
        return null;
    }

    public void logout() throws IOException {
        logger.debug("Loging out.");
        ExternalContext ec = FacesContext.getCurrentInstance().getExternalContext();
        logger.debug("Invalidating session...");
        ec.invalidateSession();
        logger.debug("Done. Forwarding to home page.");
        ec.redirect("login.xhtml");
    }

}

注册豆：

package com.dataart.mediaportal.controller.bean;

import com.dataart.mediaportal.dao.impl.UserDAOImpl;
import com.dataart.mediaportal.model.User;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.faces.application.FacesMessage;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
import javax.faces.context.FacesContext;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;

@Component
@RequestScoped
@ManagedBean(name = "registration")
@Scope("request")
public class RegistrationBean extends BaseBean {

    @Autowired(required = false)
    private UserDAOImpl userDAO;
    private String regLogin;
    private String regPassword;
    private String name;
    private String surname;
    @Autowired(required = true)
    private User user;


    public String getRegLogin() {
        return regLogin;
    }

    public void setRegLogin(String regLogin) {
        this.regLogin = regLogin;
    }

    public String getRegPassword() {
        return regPassword;
    }

    public void setRegPassword(String regPassword) {
        this.regPassword = regPassword;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSurname() {
        return surname;
    }

    public void setSurname(String surname) {
        this.surname = surname;
    }

    public String register() throws NoSuchAlgorithmException {

        MessageDigest md = MessageDigest.getInstance("MD5");
        md.update(regPassword.getBytes());
        String hash = new BigInteger(1, md.digest()).toString(16);
        user.setUserLogin(regLogin);
        user.setUserPassword(hash);
        user.setUserName(name);
        user.setUserLastname(surname);
        user.setRoleId(0);

        if (userDAO.insertUser(user)) {
            getSession(false).setAttribute("user", user);
            return "home";
        } else {
            FacesContext.getCurrentInstance().
                    addMessage(null, new FacesMessage("Registration failed!"));
            return null;
        }
    }

}

用户：

package com.dataart.mediaportal.model;

import java.io.Serializable;
import java.util.List;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import org.springframework.stereotype.Component;

@Entity
@Table(name = "users")
@NamedQueries({
    @NamedQuery(name = "User.findAll", query = "SELECT u FROM User u")})
@Component
public class User implements Serializable {

    private static final long serialVersionUID = 1L;

    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 2147483647)
    @Column(name = "user_login")
    private String userLogin;

    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 32)
    @Column(name = "user_password")
    private String userPassword;

    @Size(max = 2147483647)
    @Column(name = "user_name")
    private String userName;

    @Size(max = 2147483647)
    @Column(name = "user_lastname")
    private String userLastname;

    @Column(name = "role_id")
    private Integer roleId;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "user_id")
    private Integer userId;

    @OneToMany(mappedBy = "userId", fetch = FetchType.LAZY)
    private List<Album> albumList;

    public User() {
    }

    public User(Integer userId) {
        this.userId = userId;
    }

    public User(Integer userId, String userLogin, String userPassword) {
        this.userId = userId;
        this.userLogin = userLogin;
        this.userPassword = userPassword;
    }

    public String getUserLogin() {
        return userLogin;
    }

    public void setUserLogin(String userLogin) {
        this.userLogin = userLogin;
    }

    public String getUserPassword() {
        return userPassword;
    }

    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserLastname() {
        return userLastname;
    }

    public void setUserLastname(String userLastname) {
        this.userLastname = userLastname;
    }

    public Integer getRoleId() {
        return roleId;
    }

    public void setRoleId(Integer roleId) {
        this.roleId = roleId;
    }

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public List<Album> getAlbumList() {
        return albumList;
    }

    public void setAlbumList(List<Album> albumList) {
        this.albumList = albumList;
    }
}

堆栈跟踪：

javax.faces.FacesException: #{registration.register()}: java.lang.NullPointerException
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:89)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:374)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:662)
Caused by: javax.faces.FacesException: #{registration.register()}: java.lang.NullPointerException
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
    at javax.faces.component.UICommand.broadcast(UICommand.java:315)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    ... 25 more
Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
    ... 29 more
Caused by: java.lang.NullPointerException
    at com.dataart.mediaportal.controller.bean.RegistrationBean.register(RegistrationBean.java:69)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:278)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:274)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
    ... 30 more

【问题讨论】：

  • 您的代码有太多问题。尝试找到更合适的关于 JSF/Spring 交互的教程。如果您搜索一下，您可以找到一些有关堆栈溢出的示例。至于问题为什么，这是因为@Autowired 不能与@ManagedBean 一起使用，正如您错误地预期的那样。如您所知，这两个建议的答案都没有回答您的问题。相反，要么使 bean 由 Spring 管理，从而删除所有与 JSF 相关的注释，要么通过@ManagedProperty 注入它，从而删除所有与 Spring 相关的东西。
  • 谢谢:) 这工作得很好

标签： java spring hibernate jsf dependency-injection


【解决方案1】：

尝试从 RegistrationBean 中删除属性“userDAO”的“required = false”。

谢谢。

【讨论】：

  • 没有帮助。还有其他线索吗？
  • 您是否尝试从 RegistrationBean 中删除 '@Scope("request")'，这可能限制了 DI 注入 bean？
  • 是的，我已经试过了。我就是不明白。为什么 DI 在一个班级工作得很好而拒绝在另一个班级工作..
  • 请查看以下教程以更好地了解 JSF 和 Spring 集成。 mkyong.com/jsf2/jsf-2-0-spring-integration-example
【解决方案2】：

为了解决这个问题必须做的就是替换：

@Component
@RequestScoped
@ManagedBean(name = "loginBean")

与

@Component
@Scope("request")

对于您拥有的每个 ManagedBean，它都有自己的范围和道具。

【讨论】：

    【解决方案3】：

    当您尝试将 jsf 表单输入绑定到用户 bean 时，堆栈跟踪在注册 bean 的第 69 行指示 NPE。在登录 bean 中它工作正常，因为您没有进行任何数据绑定，而是调用 Dao 并将返回值分配给 User 对象。

    您的 NPE 结果是数据绑定问题，可能与您的 JSF 表单有关，但与 AutoWire 设置无关。

    我还会在 RegistrationBean 中为您的用户字段设置适当的 getter 和 setter 方法

    【讨论】：

    • @Autowire 是否有 getter/setter 并不重要。
    猜你喜欢
    相关资源
    最近更新 更多
    热门标签
    Java Python linux javascript C# Mysql Docker 算法 前端 SpringBoot Redis Vue spring .net 设计模式 .net core c++ kubernetes 数据库 机器学习 大数据 数据结构 微服务 js 人工智能 Go Android 面试 程序员 JVM 云原生 后端 ASP.net core 深度学习 CSS k8s git golang PHP devops Nginx Django React mybatis 架构 多线程 Spring Boot 云计算 LeetCode 分布式