getHibernateTemplate.get()返回null

本文分析了一个Struts应用中出现的登录异常问题,涉及到NullPointer异常,并提供了Spring配置、Hibernate配置及Struts配置等关键代码段,通过这些信息可以帮助开发者定位并解决类似问题。

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[color=blue][color=blue]Exception:

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: java.lang.NullPointerException
org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:535)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:433)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

root cause

java.lang.NullPointerException
struts.action.LoginAction.execute(LoginAction.java:30)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.16 logs.


这是spring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="cdao" class="dao.CustomerDao2">
<property name="sessionFactory">
<ref local="sessionFactory"/>
</property>
</bean>

<bean name="/login" class="struts.action.LoginAction">
<property name="cdao">
<ref local="cdao"/>
</property>
</bean>

<bean id="sessionFactory"
class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="configLocation"
value="/WEB-INF/hibernate.cfg.xml">
</property>
</bean></beans>


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

<!-- Generated by MyEclipse Hibernate Tools. -->
<hibernate-configuration>

<session-factory>
<property name="hbm2ddl.auto">update</property>
<property name="dialect">
org.hibernate.dialect.MySQLDialect
</property>
<property name="connection.url">
jdbc:mysql://localhost:3306/test
</property>
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<property name="connection.driver_class">
com.mysql.jdbc.Driver
</property>
<property name="myeclipse.connection.profile">MySql</property>
<property name="show_sql">true</property>
<mapping resource="po/Customer.hbm.xml" />

</session-factory>

</hibernate-configuration>


这是struts.cfg.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 1.2//EN" "http://struts.apache.org/dtds/struts-config_1_2.dtd">

<struts-config>
<data-sources />
<form-beans >
<form-bean name="cunKuanForm" type="struts.form.CunKuanForm" />
<form-bean name="loginForm" type="struts.form.LoginForm" />
<form-bean name="regForm" type="struts.form.RegForm" />
<form-bean name="quKuanForm" type="struts.form.QuKuanForm" />


</form-beans>


<global-exceptions />
<global-forwards />
<action-mappings >
<action
attribute="cunKuanForm"
input="/cunKuan.jsp"
name="cunKuanForm"
path="/cunKuan"
scope="request"
type="org.springframework.web.struts.DelegatingActionProxy" />
<action
attribute="loginForm"
input="/login.jsp"
name="loginForm"
path="/login"
scope="request"
type="org.springframework.web.struts.DelegatingActionProxy" />
<action
attribute="regForm"
input="/reg.jsp"
name="regForm"
path="/reg"
scope="request"
type="org.springframework.web.struts.DelegatingActionProxy" />
<action
attribute="quKuanForm"
input="/quKuan.jsp"
name="quKuanForm"
path="/quKuan"
scope="request"
type="org.springframework.web.struts.DelegatingActionProxy" />
<action path="/logout" type="struts.action.LogoutAction" />

</action-mappings>

<message-resources parameter="struts.ApplicationResources" />

<plug-in className="org.springframework.web.struts.ContextLoaderPlugIn">
<set-property property="contextConfigLocation"
value="/WEB-INF/applicationContext.xml" />
</plug-in>

</struts-config>


这是登陆LoginAction 的一部分:

/*
* Generated by MyEclipse Struts
* Template path: templates/java/JavaClass.vtl
*/
package struts.action;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

import po.Customer;
import struts.form.LoginForm;
import dao.CustomerDao;
import dao.ICustomerDao;


public class LoginAction extends Action {
private ICustomerDao cdao;
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
LoginForm loginForm = (LoginForm) form;// TODO Auto-generated method stub
int account = loginForm.getAccount();
String password = loginForm.getPassword();

// Customer cus = new CustomerDao().getCustomerByAccount(account);
Customer cus = cdao.getCustomerByAccount(account);
if(cus==null || !cus.getPassword().equals(password)){//登陆不成功
return new ActionForward("/error.jsp");
}
request.getSession().setAttribute("cus", cus);
request.getSession().setAttribute("admin", "admin");
return new ActionForward("/ope.jsp");

}
public ICustomerDao getCdao() {
return cdao;
}
public void setCdao(ICustomerDao cdao) {
this.cdao = cdao;
}
}


这是ICustomerDao 接口:
package dao;

import po.Customer;

public interface ICustomerDao {
public abstract boolean insertCustomer(Customer cus);

public abstract boolean updateCustomer(Customer cus);

public abstract Customer getCustomerByAccount(int account);

}


这是hibernate 调用数据库的模板:
package dao;

import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

import po.Customer;

public class CustomerDao2 extends HibernateDaoSupport implements ICustomerDao{


public Customer getCustomerByAccount(int account) {
return (Customer)this.getHibernateTemplate().get(Customer.class, account);
}

public boolean insertCustomer(Customer cus) {

return false;
}

public boolean updateCustomer(Customer cus) {
// TODO Auto-generated method stub
return false;
}

}


现在问题是用户一登陆,就报上面的异常,查了一天都没找出原因?[/color][/color]
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