使用spring的sessionFactory中的NullPointerException

我已经面对这个问题好几天了，我认为我已经尽了一切努力来找到解决这个问题的办法。我完全没有主意了

描述程序应该做什么：输入用户名和密码后，它应该连接到数据库，并检查输入的用户名/密码是否在该数据库中。由于会话工厂的空指针他从未进入该检查

堆栈跟踪：

java.lang.NullPointerException
at de.mail.HibernateUtil.getSession(HibernateUtil.java:37)
at de.mail.gui.LoginServlet.doPost(LoginServlet.java:56)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)

context.xml：

    <!-- Component Scans -->
<context:component-scan base-package="de.mail" use-default-filters="false">
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Component" />
</context:component-scan>

<!-- Datenbank -->
<bean id="c3p0DataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
    destroy-method="close">
    <property name="driverClass" value="org.postgresql.Driver" />
    <property name="jdbcUrl"
        value="****" />
    <property name="maxPoolSize" value="1" />
    <property name="properties">
        <props>
            <prop key="user">postgres</prop>
            <prop key="password">****</prop>
            <prop key="characterEncoding">UTF-8</prop>
            <!-- Properties sind nur notwendig, wenn man mal SSL für die DB-Verbindung 
                braucht (auch in der properties entkommentieren) -->
            <!-- <prop key="ssl">${db.ssl}</prop> <prop key="sslfactory">${db.sslfactory}</prop> -->
        </props>
    </property>
</bean>
<alias name="c3p0DataSource" alias="dataSource" />

<!-- TransactionManager -->
<tx:annotation-driven transaction-manager="transactionManager" />

<bean id="transactionManager"
    class="org.springframework.orm.hibernate4.HibernateTransactionManager">
    <property name="sessionFactory" ref="sessionFactory" />
    <property name="nestedTransactionAllowed" value="true" />
</bean>

<!-- SessionFactory -->
<bean id="sessionFactory"
    class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"
    destroy-method="destroy">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan">
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</prop>
            <prop key="hibernate.current_session_context_class">thread</prop>
            <prop key="hibernate.cache.provider_class">org.hibernate.cache.NoCacheProvider</prop>
            <prop key="hibernate.show_sql">true</prop>
            <prop key="hibernate.hbm2ddl.auto">update</prop>
        </props>
    </property>
    <property name="annotatedPackages">
        <list>
            <value>de.mail</value>
            <value>de.mail.data.dao</value>
            <value>de.mail.vo</value>
            <value>de.mail.gui</value>
        </list>
    </property>
    <property name="annotatedClasses">
        <list>
            <value>de.mail.data.vo.UserVO</value>
            <value>de.mail.data.vo.FilterVO</value>
            <value>de.mail.data.vo.ResultVO</value>
            <value>de.mail.data.dao.ActionDAO</value>
            <value>de.mail.HibernateUtil</value>
            <value>de.mail.FilterJob</value>
            <value>de.mail.gui.ActionServlet</value>
            <value>de.mail.gui.CreateServlet</value>
            <value>de.mail.gui.DeleteServlet</value>
            <value>de.mail.gui.EditServlet</value>
            <value>de.mail.gui.FormServlet</value>
            <value>de.mail.gui.InitServlet</value>
            <value>de.mail.gui.LoginServlet</value>
            <value>de.mail.gui.LogoutServlet</value>
            <value>de.mail.gui.RegistrationServlet</value>
        </list>
    </property>
</bean>

LoginServlet：

@Component
public class LoginServlet extends HibernateUtil {

/**
 * 
 */
private static final long serialVersionUID = -776218596462464850L;
private static final Log LOG = LogFactory.getLog(LoginServlet.class);
private static final int HEX_FF = 0xFF;

/**
 * Bearbeitet den Loginversuch<br />
 * Es werden die eingegebenen Daten ausgelesen. Aus dem Passwort wird ein Hash-Wert generiert, der mit dem Datenbankeintrag mit dem
 * passenden Usernamen verglichen wird. Stimmt alles &uumlberein wird auf die main.jsp weitergeleitet. Im Fehlerfall wird zur&uumlck auf
 * die login.jsp verwiesen.
 * 
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 * @param response der HttpResponse
 * @param request der HttpRequest
 * @throws ServletException ex
 * @throws IOException ex
 */
@Override
@Transactional(propagation = Propagation.REQUIRES_NEW)
protected void doPost(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException {

    if (!"Registrieren".equals(request.getParameter("register"))) {

        final Session session = getSession();

        // Generiert einen HashWert aus dem eingegebenen Passwort
        try {
            final byte[] pwBytes = request.getParameter("password").getBytes();
            final MessageDigest algorithm = MessageDigest.getInstance("MD5");
            algorithm.reset();
            algorithm.update(pwBytes);
            final byte[] messageDigest = algorithm.digest();

            final StringBuffer hexString = new StringBuffer();

            for (byte digest : messageDigest) {
                hexString.append(Integer.toHexString(HEX_FF & digest));
            }

            final LoginDAO dao = new LoginDAO();
            final List<UserVO> list = dao.checkLogin(request, session);

            final UserVO userVO = list.get(0);

            if (userVO.getPassword().equals(hexString.toString())) {

                request.getSession().setAttribute("userid", userVO.getId());
                final RequestDispatcher dispatcher = request.getRequestDispatcher("main.jsp");
                dispatcher.forward(request, response);

            } else {

                final RequestDispatcher dispatcher = request.getRequestDispatcher("login.jsp");
                dispatcher.forward(request, response);
            }

        } catch (NoSuchAlgorithmException nsax) {
            LOG.debug("Keine MessageDigestSpi fuer den entsprechenden Alogrithmus gefunden");

        } catch (NullPointerException npx) {
            final RequestDispatcher dispatcher = request.getRequestDispatcher("login.jsp");
            dispatcher.forward(request, response);

        } catch (IndexOutOfBoundsException ioobx) {
            final RequestDispatcher dispatcher = request.getRequestDispatcher("login.jsp");
            dispatcher.forward(request, response);
        }
    } else {
        final RequestDispatcher dispatcher = request.getRequestDispatcher("register.jsp");
        dispatcher.forward(request, response);
    }
}

/**
 * Tut nix besonders. Leiet an die doPost-Methode weiter
 * 
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 * @param response der HttpResponse
 * @param request der HttpRequest
 * @throws ServletException ex
 * @throws IOException ex
 */
@Override
protected void doGet(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException {
    doPost(request, response);
}

@组件
公共类LoginServlet扩展了HibernateUtil{
/**
* 
*/
私有静态最终长serialVersionUID=-776218596462464850L；
私有静态最终日志Log=LogFactory.getLog（LoginServlet.class）；
专用静态最终整型十六进制整FF=0xFF；
/**
*Bearbeitet den Loginversuch

*这是一个很好的解决方案，因为它是一个通用的解决方案
*passenden用户名verglichen wird.Stimmt allesüberein wird auf die main.jsp weitergeleiet.Im Fehlerfall wird zurück auf
*die login.jsp verwiesen。
* 
*@请参阅HttpServlet#doPost（HttpServletRequest请求，HttpServletResponse响应）
*@param-response-der-HttpResponse
*@param-request-der-HttpRequest
*@ServletException-ex
*@IOEX
*/
@凌驾
@事务性（传播=传播。需要\u新建）
受保护的void doPost（最终HttpServletRequest请求，最终HttpServletResponse响应）引发ServletException，IOException{
if（！“Registrieren”.equals（request.getParameter（“register”））{
最终会话=getSession（）；
//我们的总经理是一位非常优秀的工程师
试一试{
最终字节[]pwBytes=request.getParameter（“密码”）.getBytes（）；
最终MessageDigest算法=MessageDigest.getInstance（“MD5”）；
reset（）算法；
算法更新（pwBytes）；
最后一个字节[]messageDigest=algorithm.digest（）；
final StringBuffer hexString=新StringBuffer（）；
for（字节摘要：messageDigest）{
append（Integer.toHexString（HEX_FF&digest））；
}
最终登录道=新登录道（）；
最终列表=dao.checkLogin（请求、会话）；
final UserVO UserVO=list.get（0）；
if（userVO.getPassword（）.equals（hextString.toString（）））{
request.getSession（）.setAttribute（“userid”，userVO.getId（））；
final RequestDispatcher=request.getRequestDispatcher（“main.jsp”）；
转发（请求、响应）；
}否则{
final RequestDispatcher=request.getRequestDispatcher（“login.jsp”）；
转发（请求、响应）；
}
}捕获（NoSuchAlgorithmException nsax）{
LOG.debug（“Keine MessageDigestSpi fuer den entsprechenden alogritthmus gefunden”）；
}捕获（NullPointerException npx）{
final RequestDispatcher=request.getRequestDispatcher（“login.jsp”）；
转发（请求、响应）；
}捕获（IndexOutOfBoundsException ioobx）{
final RequestDispatcher=request.getRequestDispatcher（“login.jsp”）；
转发（请求、响应）；
}
}否则{
final RequestDispatcher=request.getRequestDispatcher（“register.jsp”）；
转发（请求、响应）；
}
}
/**
*这是一个很好的方法
* 
*@参见HttpServlet#doGet（HttpServletRequest请求，HttpServletResponse响应）
*@param-response-der-HttpResponse
*@param-request-der-HttpRequest
*@ServletException-ex
*@IOEX
*/
@凌驾
受保护的void doGet（最终HttpServletRequest请求，最终HttpServletResponse响应）抛出ServletException，IOException{
doPost（请求、响应）；
}

---

我真的没有发现这个错误。我检查了每个文件，特别是spring上下文中缺少的内容，但什么也没有发现。我认为这个错误是由一些非常简单的原因造成的。对我来说——我对spring和hibernate非常陌生——这个错误不想被发现。

尝试为HibernateUtil编写以下代码

import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.SessionFactory;


    public class HibernateUtil {

        private static final SessionFactory sessionFactory;

        static {
            try {
                // Create the SessionFactory from standard (hibernate.cfg.xml) 
                // config file.
                sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
            } catch (Throwable ex) {
                // Log the exception. 
                System.err.println("Initial SessionFactory creation failed." + ex);
                throw new ExceptionInInitializerError(ex);
            }
        }

        public static SessionFactory getSessionFactory() {
            return sessionFactory;
        }
    }

下面的代码将指导您如何使用上述类

HibernateUtil hu= new HibernateUtil();
SessionFactory sessionFactory =hu.getSessionFactory();
Session session = sessionFactory.openSession();
Query q = session.createQuery ("from UserM where userid='"+lf.getUser()+"' and userpass='"+lf.getPassword()+"'");

---

尝试“c3p0DataSource”引用SessionFactory bean，而不是使用别名。

您的

LoginServlet

有一个

@Component

注释，这将使其成为spring管理的bean，但是您的web.xml中可能还有一个servlet声明。您现在有两个servlet实例，一个由spring管理（而且非常无用，因为它不在其他地方使用）和一个由web容器管理的实例，它不使用

@Autowired

要解决您的问题，请使用依赖项查找而不是尝试进行依赖项注入。为此，请使用servlet的

init

方法，只需删除

HibernateUtil

类和

@组件

注释

public class LoginServlet extends HttpServlet {

    private SessionFactory sessionFactory;

    public void init() {
        ApplicationContext ctx = WebApplicationContext.getApplicationContext(getServletContext());
        sessionFactory = ctx.getBean(SessionFactory.class);
    }

    protected Session getSession() {
        return sessionFactory.getCurrentSession();
    }
    …
}

您的

@Transactional

永远不会工作，因为bean不是spring管理的，而注释基本上什么都不做。您可以通过将

doPost

方法包装到

TransactionTemplate

中来解决这一问题

<bean id="txTemplate"  class="TransactionTemplate">
    <constructor-arg ref="transactionManager" />
</bean>

将原始的

doPost

方法重命名为

doPostInternal

，并可以选择将其设置为

private

，然后添加以下

doPost

方法`

protected void doPost(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException {
    txTemplate.execute(new TransactionCallbackWithoutResult() {
        public void doInTransactionWithoutResult(TransactionStatus status) {
            doPostInternal(request,response);
        }
    });
}

最后，您的hibernate配置也有缺陷，因为您正在乱搞

hibernate.current\u session\u context\u class

。使用spring时，除非您使用的是JTA，否则您应该保留此属性。查看您的配置，您不需要删除该属性的设置，当前设置会中断正常的spring与冬眠的融合

我强烈建议你采取行动

public class LoginServlet extends HttpServlet {

    private TransactionTemplate txTemplate;

    public void init() {
        ApplicationContext ctx = WebApplicationContext.getApplicationContext(getServletContext());
        …
        txTemplate = ctx.getBean(TransactionTemplate.class);
    }

protected void doPost(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException {
    txTemplate.execute(new TransactionCallbackWithoutResult() {
        public void doInTransactionWithoutResult(TransactionStatus status) {
            doPostInternal(request,response);
        }
    });
}