0

我最近开始使用去年学习 Ruby 的 Java 后端。我正在尝试做一个简单的“发布”操作，将联系人保存到 MySQL 数据库。（请原谅新手问题）。

我正在使用条纹、JPA 和休眠。我一直在关注关于为 MVC 设置环境的Stripes 书，但我有点陷入以下错误，我希望有人能指出我正确的方向。我知道错误说我有一个未处理的异常，但我还不够新，我不确定这是否是错误的真正原因，我不确定它是 Hibernate、Java 还是 Stripes 问题。我确定我错过了一些东西，我只是不确定是什么。我将错误与我的一些代码一起发布。

谢谢您的帮助

错误：

Feb 19, 2013 6:13:38 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [StripesDispatcher] in context with path [] threw exception [Unhandled exception in exception handler.] with root cause
java.lang.NullPointerException
    at veexterior.DAO.impl.BaseDaoImpl.save(BaseDaoImpl.java:46)
    at veexterior.action.ContactActionBean.save(ContactActionBean.java:36)
    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 net.sourceforge.stripes.controller.DispatcherHelper$6.intercept(DispatcherHelper.java:456)
    at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:158)
    at net.sourceforge.stripes.controller.BeforeAfterMethodInterceptor.intercept(BeforeAfterMethodInterceptor.java:113)
    at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155)
    at net.sourceforge.stripes.controller.ExecutionContext.wrap(ExecutionContext.java:74)
    at net.sourceforge.stripes.controller.DispatcherHelper.invokeEventHandler(DispatcherHelper.java:454)
    at net.sourceforge.stripes.controller.DispatcherServlet.invokeEventHandler(DispatcherServlet.java:278)
    at net.sourceforge.stripes.controller.DispatcherServlet.service(DispatcherServlet.java:160)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at net.sourceforge.stripes.controller.StripesFilter.doFilter(StripesFilter.java:260)
    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:225)
    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:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
    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:1001)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:680)

BaseDAOImpl

package veexterior.DAO.impl;

import org.stripesstuff.stripersist.Stripersist;

import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import javax.persistence.NonUniqueResultException;
import javax.persistence.NoResultException;
import javax.persistence.Query;
import java.util.List;
import veexterior.DAO.Dao;
import veexterior.models.Contact;


public abstract class BaseDaoImpl<T,ID extends Serializable>
    implements Dao<T,ID>
{
    private Class<T> entityClass;

    @SuppressWarnings("unchecked")
    public BaseDaoImpl() {
        entityClass = (Class<T>)
            ((ParameterizedType) getClass().getGenericSuperclass())
            .getActualTypeArguments()[0];
    }
    /* methods... */


    @SuppressWarnings("unchecked")
    public List<T> read() {
        return Stripersist.getEntityManager()
            .createQuery("from " + entityClass.getName())
            .getResultList();
    }
    public T read(ID id) {
        return Stripersist.getEntityManager().find(entityClass, id);
    }


    @SuppressWarnings("unchecked")
    public void save(T object) {
        Stripersist.getEntityManager().persist(object);
    }
    public void delete(T object) {
        Stripersist.getEntityManager().remove(object);
    }
    public void commit() {
        Stripersist.getEntityManager().getTransaction().commit();
    }


    @SuppressWarnings("unchecked")
    public T findBy(String fieldName, Object value) {
        Query query = Stripersist.getEntityManager()
            .createQuery(getQuery(fieldName, null))
            .setParameter(fieldName, value);
        return getSingleResult(query);
    }

    private String getQuery(String fieldName, Contact contact){
        String query =
            "from " + entityClass.getName() + " t " +
            "where t." + fieldName + " = :" + fieldName;
        if (contact == null) {
            return query;
        }
        return query + " and t.user = :user";
    }
    @SuppressWarnings("unchecked")
    private T getSingleResult(Query query) {
        try {
            return (T) query.getSingleResult();
        }
        catch (NonUniqueResultException exc) {
            return (T) query.getResultList().get(0);
        }
        catch (NoResultException exc) {
            return null;
        }
    }

}

联系ActionBean

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package veexterior.action;

import net.sourceforge.stripes.action.DefaultHandler;
import net.sourceforge.stripes.action.ForwardResolution;
import net.sourceforge.stripes.action.RedirectResolution;
import net.sourceforge.stripes.action.Resolution;
//import net.sourceforge.stripes.action.SimpleMessage;
import veexterior.models.Contact;
/**
 *
 * @author dave
 */
public class ContactActionBean extends BaseActionBean {
    private static final String FORM="/WEB-INF/contactus.jsp";

    private Contact contact;

    public Contact getContact() {
        return contact;
    }

    public void setContact(Contact contact) {
        this.contact = contact;
    }

    @DefaultHandler
    public Resolution form() {/* (1) */
        return new ForwardResolution(FORM);
    }
    public Resolution save() {
        Contact contact = getContact();
        contactDao.save(contact);
        contactDao.commit();
        return new RedirectResolution(ContactActionBean.class);
    }
}

用于提交的表格

                <stripes:form beanclass="veexterior.action.ContactActionBean">                   
                    <div class="control-group">
<!--                    <label class="control-label" for="inputEmail">Email</label>-->
                    <div class="controls">
                        <input type="text" id="inputEmail" placeholder="Email" name="contact.email">
                    </div>
                    </div>
                    <div class="control-group">
<!--                        <label class="control-label" for="inputName">Name</label>-->
                        <div class="controls">
                            <input type="text" id="inputName" placeholder="Full Name" name="contact.name">
                        </div>

                    </div>
                    <div class="control-group">
<!--                        <label class="control-label" for="inputName">Company</label>-->
                        <div class="controls">
                            <input type="text" id="inputName" placeholder="Company" name="contact.company">
                        </div>

                    </div>                    
                    <div class="control-group">
                        <textarea rows="5" class="input-xlarge" id="contactusmessage" name="contact.message" placeholder="Enter your message details."></textarea>
                    </div>    
                    <div class="control-group">
                        <div class="controls">
                        <button type="submit" class="btn" name="save">Send it</button>
                        </div>
                    </div>
                </stripes:form>

我一直在关注的书中的一些代码

package stripesbook.dao.impl.stripersist;


import org.stripesstuff.stripersist.Stripersist;

import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.util.List;
import javax.persistence.NonUniqueResultException;
import javax.persistence.NoResultException;
import javax.persistence.Query;
import stripesbook.dao.Dao;
import stripesbook.model.User;


public abstract class BaseDaoImpl<T,ID extends Serializable>
    implements Dao<T,ID>
{
    private Class<T> entityClass;

    @SuppressWarnings("unchecked")
    public BaseDaoImpl() {
        entityClass = (Class<T>)
            ((ParameterizedType) getClass().getGenericSuperclass())
            .getActualTypeArguments()[0];
    }
    /* methods... */


    @SuppressWarnings("unchecked")
    public List<T> read() {
        return Stripersist.getEntityManager()
            .createQuery("from " + entityClass.getName())
            .getResultList();
    }
    public T read(ID id) {
        return Stripersist.getEntityManager().find(entityClass, id);
    }


    @SuppressWarnings("unchecked")
    public void save(T object) {
        Stripersist.getEntityManager().persist(object);
    }
    public void delete(T object) {
        Stripersist.getEntityManager().remove(object);
    }
    public void commit() {
        Stripersist.getEntityManager().getTransaction().commit();
    }


    @SuppressWarnings("unchecked")
    public T findBy(String fieldName, Object value) {
        Query query = Stripersist.getEntityManager()
            .createQuery(getQuery(fieldName, null))
            .setParameter(fieldName, value);
        return getSingleResult(query);
    }
    @SuppressWarnings("unchecked")
    public T findBy(String fieldName, Object value, User user) {
        Query query = Stripersist.getEntityManager()
            .createQuery(getQuery(fieldName, user))
            .setParameter(fieldName, value)
            .setParameter("user", user);
        return getSingleResult(query);
    }
    private String getQuery(String fieldName, User user){
        String query =
            "from " + entityClass.getName() + " t " +
            "where t." + fieldName + " = :" + fieldName;
        if (user == null) {
            return query;
        }
        return query + " and t.user = :user";
    }
    @SuppressWarnings("unchecked")
    private T getSingleResult(Query query) {
        try {
            return (T) query.getSingleResult();
        }
        catch (NonUniqueResultException exc) {
            return (T) query.getResultList().get(0);
        }
        catch (NoResultException exc) {
            return null;
        }
    }


}

XML 文件

<?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_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>MyAppsNAme</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>

    <filter>
            <display-name>Stripes Filter</display-name>
            <filter-name>StripesFilter</filter-name>
            <filter-class>net.sourceforge.stripes.controller.StripesFilter</filter-class>
            <init-param>
                    <param-name>ActionResolver.Packages</param-name>
                    <param-value>veexterior</param-value>
            </init-param>
            <init-param>
                <param-name>Extension.Packages</param-name>
                <param-value>org.stripesstuff.stripersist</param-value>
            </init-param>
    </filter>

    <filter-mapping>
            <filter-name>StripesFilter</filter-name>
            <url-pattern>*.jsp</url-pattern>
            <dispatcher>REQUEST</dispatcher>
    </filter-mapping>

    <filter-mapping>
            <filter-name>StripesFilter</filter-name>
            <servlet-name>StripesDispatcher</servlet-name>
            <dispatcher>REQUEST</dispatcher>
    </filter-mapping>

    <servlet>
            <servlet-name>StripesDispatcher</servlet-name>
            <servlet-class>net.sourceforge.stripes.controller.DispatcherServlet</servlet-class>
            <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
            <servlet-name>StripesDispatcher</servlet-name>
            <url-pattern>*.action</url-pattern>
    </servlet-mapping>
</web-app>

Persistence.xml 文件

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="persistence" transaction-type="RESOURCE_LOCAL">
    <!--  Tell JPA to use Hibernate  -->
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <properties>
      <!--  Autodetect entity classes  -->
      <property name="hibernate.archive.autodetection" value="class"/>
      <!--  Automatically create the SQL schema  -->
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <!--  Tell Hibernate to use MySQL  -->
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
      <property name="hibernate.connection.username" value=""/>
      <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
      <property name="hibernate.connection.password" value=""/>
      <property name="hibernate.connection.url" value="Local MySQL Address"/>
      <property name="hibernate.cache.provider_class" value="org.hibernate.cache.NoCacheProvider"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <!--  Configure the connection pool  -->
      <property name="hibernate.c3p0.min_size" value="5"/>
      <property name="hibernate.c3p0.max_size" value="20"/>
      <property name="hibernate.c3p0.timeout" value="300"/>
      <property name="hibernate.c3p0.max_statements" value="50"/>
      <property name="hibernate.c3p0.idle_test_period" value="3000"/>
    </properties>
  </persistence-unit>
</persistence>

在此处输入图像描述

4

2 回答 2

0

你有有效的persistence.xml吗？您需要它来配置数据源。最后，它必须位于/WEB-INF/classes/META-INF/persistence.xml正确启用 Java Persistence 的位置。

于 2013-02-19T14:00:26.327 回答
0

您是否将 Stripersist 包 (org.stripesstuff.stripersist) 添加到 web.xml 中的 Extension.Packages 列表中？省略这将解释 NPE。

于 2013-02-19T13:36:34.190 回答