Struts2 + Spring 3.2 + Hibernate 3 java.lang.NullPointerException（執行中）

我有一個例子的問題。Struts2 + Spring 3.2 + Hibernate 3 java.lang.NullPointerException（執行中）

當我列出操作中的元素時出現此錯誤，但我不知道爲什麼。

我認爲這個bean沒有被創建，因爲當調用動作時會發生錯誤。

Struts的問題報告：

Struts has detected an unhandled exception: 
Messages: 
File: actions/ListingAction.java 
Line number: 26

蹤跡：

java.lang.NullPointerException  
    actions.ListingAction.execute(ListingAction.java:26) 
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
    java.lang.reflect.Method.invoke(Method.java:597) 
    com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:446) 
    com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:285) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) 
    org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176) 
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265) 
    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) 
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:238) 
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:238) 
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:252) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171) 
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) 
    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54) 
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:544) 
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77) 
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91) 
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
    com.opensymphony.sitemesh.webapp.SiteMeshFilter.obtainContent(SiteMeshFilter.java:129) 
    com.opensymphony.sitemesh.webapp.SiteMeshFilter.doFilter(SiteMeshFilter.java:77) 
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
    org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:233) 
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
    org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) 
    org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) 
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) 
    org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) 
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) 
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947) 
    org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) 
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) 
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009) 
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589) 
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310) 
    java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895) 
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918) 
    java.lang.Thread.run(Thread.java:680)

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_3_0.xsd" 
    version="3.0"> 

    <display-name>PFC</display-name> 

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

      <!-- Spring --> 

    <context-param> 
     <param-name>contextConfigLocation</param-name> 
     <param-value> 
      /WEB-INF/applicationContext*.xml 
     </param-value> 
    </context-param> 
    <listener> <!-- Required for the struts2 spring plugin to work --> 
     <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> 
    </listener> 
    <listener> 
     <listener-class>org.springframework.web.util.IntrospectorCleanupListener</listener-class> 
    </listener> 
    <listener> 
     <listener-class>org.springframework.web.context.request.RequestContextListener</listener-class> 
    </listener> 

    <filter> <!-- Get spring to keep the session open for the whole request, so hibernate's lazy loads work --> 
     <filter-name>openSessionInViewFilter</filter-name> 
     <filter-class>org.springframework.orm.hibernate3.support.OpenSessionInViewFilter</filter-class> 
    </filter> 

    <filter-mapping> 
     <filter-name>openSessionInViewFilter</filter-name> 
     <url-pattern>/*</url-pattern> 
    </filter-mapping> 

<!-- Sitemesh (needs to be before struts) --> 
    <filter> 
     <filter-name>sitemesh</filter-name> 
     <filter-class>com.opensymphony.sitemesh.webapp.SiteMeshFilter</filter-class> 
    </filter> 

    <filter-mapping> 
     <filter-name>sitemesh</filter-name> 
     <url-pattern>/*</url-pattern> 
    </filter-mapping> 

<!-- Struts2 config (needs to be after sitemesh) --> 


    <filter> 
     <filter-name>struts2</filter-name> 
     <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> 
    </filter> 

    <filter-mapping> 
     <filter-name>struts2</filter-name> 
     <url-pattern>/*</url-pattern> 
    </filter-mapping> 

    <session-config> 
     <session-timeout> 
      30 
     </session-timeout> 
    </session-config> 

<!-- La configuración de los struts.. el nombre se pone registro el fichero de confi-spring en registro-struts.xml--> 


</web-app>

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:aop="http://www.springframework.org/schema/aop" 
     xmlns:tx="http://www.springframework.org/schema/tx" 
     xsi:schemaLocation="http://www.springframework.org/schema/beans 
     http://www.springframework.org/schema/beans/spring-beans-3.2.xsd 
     http://www.springframework.org/schema/tx 
     http://www.springframework.org/schema/tx/spring-tx-3.2.xsd 
     http://www.springframework.org/schema/aop 
     http://www.springframework.org/schema/aop/spring-aop-3.2.xsd"> 


    <!-- The singleton hibernate session factory --> 
    <bean id="sessionFactory" 
      class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> 
     <property name="configLocation" value="classpath:hibernate.cfg.xml"/> 
    </bean> 

    <!-- Spring's hibernate transaction manager, in charge of making hibernate sessions/txns --> 
    <bean id="transactionManager" 
      class="org.springframework.orm.hibernate3.HibernateTransactionManager"> 
     <property name="sessionFactory" ref="sessionFactory"/> 
    </bean> 

    <bean id="sessionLocaleResolver" 
      class="org.springframework.web.servlet.i18n.SessionLocaleResolver"/> 

    <bean id="eventoService" class="services.EventoService" scope="singleton"> 
     <property name="sessionFactory" ref="sessionFactory"/> 
     <!--property name="sessionFactory" ref="sessionFactory"/--> 
    </bean> 

    <bean id="listingAction" class="actions.ListingAction"> 
     <property name="serviceEvento" ref="eventoService"/> 
    </bean> 


</beans>

struts.xml：

<?xml version="1.0" encoding="UTF-8"?> 
<!DOCTYPE struts PUBLIC 
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN" 
"http://struts.apache.org/dtds/struts-2.3.dtd"> 

<struts> 
    <constant name="struts.devMode" value="true" /> <!-- set to false for prod --> 

    <constant name="struts.configuration.xml.reload" value="true" /> 

    <package name="eventos" extends="struts-default"> 
     <action name="ListingAction" class="actions.ListingAction"> 
      <result name="success">/vistas/eventos/Listing.jsp</result> 
     </action> 
    </package> 

    <constant name="struts.objectFactory" value="org.apache.struts2.spring.StrutsSpringObjectFactory" /> 


</struts>

hibernate.cfg.xml：

<?xml version='1.0' encoding='utf-8'?> 
<!DOCTYPE hibernate-configuration PUBLIC 
"-//Hibernate/Hibernate Configuration DTD//EN" 
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 

<hibernate-configuration> 
<session-factory> 
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> 
<property name="hibernate.connection.url"> jdbc:mysql://localhost:3306/events</property> 
<property name="hibernate.connection.username">eventuser</property> 
<property name="connection.password">eventuser</property> 
<property name="connection.pool_size">1</property> 
<property name="hibernate.dialect"> org.hibernate.dialect.MySQLDialect</property> 
<property name="show_sql">true</property> 
<property name="hbm2ddl.auto">create</property> 
<mapping resource="model/Evento.hbm.xml"/> 
</session-factory> 
</hibernate-configuration>

ListingAction.java：

package actions; 

import com.opensymphony.xwork2.ActionSupport; 
import services.EventoService; 
import java.util.List; 
import model.Evento; 
/** 
* 
* @author 
*/ 
public class ListingAction extends ActionSupport{ 


// So that spring can inject the business singleton 
    protected EventoService serviceEvento; 

    public void setServiceEvento(EventoService value) { 
     serviceEvento=value; 
    } 

    public String execute() { 
     events = serviceEvento.getEvents(); 
     return "success"; 
    } 

    List<Evento> events; 
    public List<Evento> getEvents() { return events; } 

    // For redirect results 
    protected String redirectUrl; 

    public String getRedirectUrl() { 
     return redirectUrl; 
    } 
    public String redirect(String to) { 
     redirectUrl = to; 
     return "redirect"; 
    } 
}

EventoService.java：

package services; 

import java.util.List; 
import model.Evento; 
import org.hibernate.SessionFactory; 
import org.hibernate.Session; 

/** 
* 
* @author 
*/ 
public class EventoService { 

    SessionFactory sessionFactory; 
    public void setSessionFactory(SessionFactory value) { 
     sessionFactory = value; 
    } 

    // Shortcut for sessionFactory.getCurrentSession() 
    public Session sess() { 
     return sessionFactory.getCurrentSession(); 
    } 

    public Evento getEventById(long id) { 
     return (Evento) sess().load(Evento.class, id); 
    } 


    public void deleteEventById(long id) { 
     sess().delete(getEventById(id)); 
    } 


    public void createEvent(String name) { 
     Evento theEvent = new Evento(); 
     theEvent.setName(name); 
     sess().save(theEvent); 

    } 

    @SuppressWarnings("unchecked") 
    public List<Evento> getEvents() { 
      System.out.println("\n\nGET EVENTS SERVICE"); 
     return sess().createQuery("from Event").list(); 
    } 


}

來源

2013-08-05 Lore Lai

什麼是空？ ... –

'actions.ListingAction.execute（ListingAction.java:26）' - 第26行有什麼？ –

反正我已經在github上上傳了一個更簡單的struts2-spring3-hibernate3示例 - https://github.com/coding-idiot/Struts2-Examples –

// So that spring can inject the business singleton 
protected EventoService serviceEvento; 

public void setServiceEvento(EventoService value) { 
    serviceEvento=value; 
}

糟糕，更換到

// So that spring can inject the business singleton 
protected EventoService eventoService; 

public void setEventoService(EventoService value) { 
    eventoService=value; 
}

這些變化到導線與id="eventoService"配置在所述彈簧配置於所述對象是必需動作屬性。該行動由支柱容器管理，默認情況下它的名字

 
### specifies the autoWiring logic when using the SpringObjectFactory. 
### valid values are: name, type, auto, and constructor (name is the default) 
struts.objectFactory.spring.autoWire = name

使用自動裝配策略無需佈線的對象正確Struts是無法從注入Spring容器的依賴。因此，操作屬性serviceEvento未初始化並引發NPE。您可以通過type或auto嘗試其他自動裝配策略。

另一種方法是讓春天來管理操作對象：

來源

2013-08-05 19:15:51

這會造成什麼區別？ –

@StevenBenitez它會更改自動裝配屬性的名稱。 –

非常感謝。這是錯誤。 –

我明白爲什麼你得到一個空指針異常。在您的applicationContext.xml中，您要求spring創建一個實例actions.ListingAction，並在創建的操作類中注入一個serviceEvento的實例。這是完美的，它是假設工作。

在您的struts.xml中，您指定spring將負責通過指定<constant name="struts.objectFactory" value="org.apache.struts2.spring.StrutsSpringObjectFactory" />來創建您的操作，這也很完美。

我認爲你正在使用的空指針是struts.xml中下面的配置的結果。

<action name="ListingAction" class="actions.ListingAction"> 
     <result name="success">/vistas/eventos/Listing.jsp</result> 
    </action>

在這裏，您指定的actions.ListingAction的完整路徑，其結果是創造了這個類，並在執行你的行動中。之前在applicationContext.xml中創建的實例未使用。那是你空指針的來源，serviceEvento默認使用這種創建方法爲null。這就是爲什麼你有一個空指針。

解決方案

更換你的動作類的struts.xml您在applicationContext.xml定義的bean名稱的完整路徑。也就是說

從

<action name="ListingAction" class="actions.ListingAction"> 
     <result name="success">/vistas/eventos/Listing.jsp</result> 
    </action>

要

<action name="ListingAction" class="listingAction"> 
     <result name="success">/vistas/eventos/Listing.jsp</result> 
    </action>

讓我知道如果這能解決你的問題。

來源

2013-08-06 05:12:00

Struts2 + Spring 3.2 + Hibernate 3 java.lang.NullPointerException（執行中）

回答

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