ssh整合出现空指针错误

Question

web.xml中的配置<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
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_2_5.xsd">
 
 <filter>
  <filter-name>struts2</filter-name> 
  <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> 
  </filter>
 <filter-mapping>
  <filter-name>struts2</filter-name> 
  <url-pattern>/*</url-pattern> 
  </filter-mapping>
<context-param>
  
   <param-name>contextConfigLocation</param-name>
   <param-value>/WEB-INF/applicationContext.xml</param-value>
  </context-param>
  
<servlet>
 <servlet-name>context</servlet-name>
 <servlet-class>org.springframework.context.ContextLoaderServlet</servlet-class>
 <load-on-startup>1</load-on-startup>
</servlet>  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>
dao中的代码
[code=Java]
public String login(){
boolean flag=true;
String hql="from Abc";
System.out.println("+++++++++++++++==");
List list = getHibernateTemplate().find("from Abc");
if(list.isEmpty()){
System.out.println("-------------------");
}
//System.out.println(list.get(1));
return "aaa";
}
List list = getHibernateTemplate().find("from Abc");，这一句出现空指针异常，怎么解决呢？
[/code]

Answer 1

Abc  这个pojo类 有问题  ,贴的代码太少了

Answer 2

description The server encountered an internal error () that prevented it from fulfilling this request.exception java.lang.NullPointerException
com.demo.LoginDao.login(LoginDao.java:13)
com.demo.LoginAction.execute(LoginAction.java:22)
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:441)
com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:280)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:243)
com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:165)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:252)
org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:179)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:130)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:165)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:179)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:488)
org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.30 logs.
这是错误信息，在jsp页面上显示的

Answer 3

看不出是哪的问题 Abc这个实体类 在配置文件里边配好了吗 我老感觉是配置出了问题 

Answer 4

这个是Abc的pojo
public class Abc implements java.io.Serializable { // Fields private Integer username; private String password; // Constructors /** default constructor */
public Abc() {
} /** full constructor */
public Abc(Integer username, String password) {
this.username = username;
this.password = password;
} // Property accessors public Integer getUsername() {
return this.username;
} public void setUsername(Integer username) {
this.username = username;
} public String getPassword() {
return this.password;
} public void setPassword(String password) {
this.password = password;
}}
这个是struts.xml的配置文件
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd"><struts>
<package name="login" extends="struts-default">
<action name="login" class="com.demo.LoginAction">
<result name="success">success.jsp</result>
</action>
</package>
</struts>这个是application中的配置文件
<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
<bean id="mdatasource"
class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName"
value="com.mysql.jdbc.Driver">
</property>
<property name="url" value="jdbc:mysql://localhost:3306/test"></property>
<property name="username" value="root"></property>
<property name="password" value="root"></property>
</bean>
<bean id="mysessionfactory"
class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource">
<ref bean="mdatasource" />
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">
org.hibernate.dialect.MySQLDialect
</prop>
</props>
</property>
<property name="mappingResources">
<list>
<value>com/demo/Abc.hbm.xml</value></list>
</property></bean>


<bean id="logindao" class="com.demo.LoginDao">
<property name="sessionFactory">
<ref bean="mysessionfactory"/>
</property>
</bean>
<bean name="loginAction" class="com.demo.LoginAction">
<property name="logindao">
<ref bean="logindao"/>
</property>
</bean>
</beans>

Answer 5

   有两种情况：1.你使用的是HibernateDaoSupport，你需要在applicationContext.xml中配置hibernateTemplate，指向sessionFactory,否则，你使用HibernateDaoSupport没有数据库连接，报空指针，
                2.可能是你Action层没有注入进去。               我觉得第一种可能性大点。因为我看了你的配置，没有hibernateTemplate指向 <bean id="logindao" class="com.demo.LoginDao">
            <property name="hibernateTemplate">
                <ref bean="hibernateTemplate"/>
            </property>
 </bean>
<bean id="hibernateTemplate" class="org.springframework.orm.hibernate3....">
   <property name="sessionFactory" ref="mysessionfactory">
</bean>  你照我的改一下试一试

Answer 6

<bean id="hibernateTemplate" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="sessionFactory" ref="mysessionfactory">
</property>
</bean>
<bean id="logindao" class="com.demo.LoginDao">
<property name="hibernateTemplate">
<ref bean="hibernateTemplate"/>
</property>
</bean>
<bean name="loginAction" class="com.demo.LoginAction">
<property name="logindao">
<ref bean="logindao"/>
</property>
</bean>
这是我所更改的代码，可问题还是存在

Answer 7

这是Abc.hbm.xml代码
  <?xml version="1.0" encoding="utf-8" ?> 
  <!DOCTYPE hibernate-mapping (View Source for full doctype...)> 
- <!--  
    Mapping file autogenerated by MyEclipse Persistence Tools  --> 
- <hibernate-mapping default-cascade="none" default-access="property" default-lazy="true" auto-import="true">
- <class name="com.demo.Abc" table="abc" catalog="test" mutable="true" polymorphism="implicit" dynamic-update="false" dynamic-insert="false" select-before-update="false" optimistic-lock="version">
- <id name="username" type="java.lang.Integer">
  <column name="username" /> 
  <generator class="assigned" /> 
  </id>
- <property name="password" type="java.lang.String" unique="false" optimistic-lock="true" lazy="false" generated="never">
  <column name="password" length="45" not-null="true" /> 
  </property>
  </class>
  </hibernate-mapping>

Answer 8

List list = getHibernateTemplate().find("from Abc");，这一句出现空指针异常，很明显是没有get到HibernateTemplate，楼主去掉这一句看看是否报错，如果报了那说明是配置的问题，没报就找一下关于getHibernateTemplate()的代码。

Answer 9

没报，getHibernateTemplate()得到的是null，现在的问题是在Action中调用不了dao

Answer 10

楼主能给出包含getHibernateTemplate()的类文件的代码么？

Answer 11

Action中调用不了dao是你配置文件的错，你给出来我看看。

Answer 12

web.xml有没有配置
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/applicationContext-*.xml
</param-value>
</context-param><listener>
<listener-class>
           org.springframework.web.context.ContextLoaderListener
        </listener-class>
</listener>

Answer 13

getHibernateTemplate()的文件代码，我是直接调用的，没有文件。
web.xml中的配置文件<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
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_2_5.xsd">
 
 <filter>
  <filter-name>struts2</filter-name> 
  <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> 
  </filter>
 <filter-mapping>
  <filter-name>struts2</filter-name> 
  <url-pattern>/*</url-pattern> 
  </filter-mapping>
<context-param>
  
   <param-name>contextConfigLocation</param-name>
   <param-value>/WEB-INF/applicationContext.xml</param-value>
  </context-param>
  
<servlet>
    <servlet-name>context</servlet-name>
    <servlet-class>org.springframework.web.context.ContextLoaderServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>applicationContext中的配置文件<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
<bean id="mdatasource"
class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName"
value="com.mysql.jdbc.Driver">
</property>
<property name="url" value="jdbc:mysql://localhost:3306/test"></property>
<property name="username" value="root"></property>
<property name="password" value="root"></property>
</bean>
<bean id="mysessionfactory"
class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource">
<ref bean="mdatasource" />
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">
org.hibernate.dialect.MySQLDialect
</prop>
</props>
</property>
<property name="mappingResources">
<list>
<value>com/demo/Abc.hbm.xml</value></list>
</property></bean>
<bean id="logindao" class="com.demo.LoginDao">
<property name="sessionFactory">
<ref bean="mysessionfactory"/>
</property>
</bean>

<bean name="loginAction" class="com.demo.LoginAction">
<property name="logindao">
<ref bean="logindao"/>
</property>
</bean>
</beans>

Answer 14

web.xml中加上
<listener>
<listener-class>
  org.springframework.web.context.ContextLoaderListener
  </listener-class>
</listener>
报404错误The requested resource () is not available.我用的是
<servlet>
    <servlet-name>context</servlet-name>
    <servlet-class>org.springframework.web.context.ContextLoaderServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

Answer 15

你的配置文件是不是放在这个地方啊  /WEB-INF/applicationContext.xml

Answer 16

配置文件的地址正确
这是我的actionpackage com.demo;import java.util.List;
import com.opensymphony.xwork2.ActionSupport;public class LoginAction extends ActionSupport {
LoginDao logindao;

public LoginDao getLogindao() {
return logindao;
} public void setLogindao(LoginDao logindao) {
this.logindao = logindao;
}

public String execute(){
System.out.println("-------------------");
logindao.login();
return "success";
}
}

Answer 17

实在没看出代码和配置哪里出问题，1.重新检查lib里面的jar 试试看
2.把防火墙关了 试试看
3.window-preferences-java-compiler 选择版本和tomcat一致的 ，你的tomcat是5.5 就选5.0 试试看
4.实在不行换个tomcat 试试看

Answer 18

web.xml中  
 <context-param>
  
      <param-name>contextConfigLocation</param-name>
      <param-value>/WEB-INF/applicationContext.xml</param-value>
  </context-param>
你的applicationContext.xml放的位置好像不对吧.

Answer 19

List list = getHibernateTemplate().find("from Abc")；
这个getHibernateTemplate()怎么来的啊？不明白....不是loginDao的吗？
是不是应该是loginDao.getHibernateTemplate()啊？

Answer 20

当初注入的SessionFactory或HibernateTemplate为空
调用getHibernateTemplate()，你得到的HibernateTemplate对象为空了
感觉就是这个问题了

Answer 21

Action类调用不了dao类？什么原因？