高手进来看看啊
代码如下
public class SpringBaseBeanAction extends ActionSupport{
String beanName= " ";
public SpringBaseBeanAction(){
}
public SpringBaseBeanAction(String beanName){
this.beanName=beanName;
}
public Object getBean(String beanName){
WebApplicationContext webapp=getWebApplicationContext();
Object obj=webapp.getBean(beanName);
return obj;
}
public Object getBean(){
WebApplicationContext webapp=getWebApplicationContext();
return webapp.getBean(beanName);
}
}
以上是调用getBean(String beanName)得到类的实例
package com.txForum.dao;
import net.sf.hibernate.Query;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;
import org.springframework.orm.hibernate3.HibernateCallback;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;
import java.util.*;
public class CommonUserDao extends HibernateDaoSupport {
private static final Log log = LogFactory.getLog(CommonUserDao.class);
protected void initDao() {
//do nothing
}
public List ExecQueries(final String sql){
return (List)getHibernateTemplate().execute(new HibernateCallback(){
public List doInHibernate(Session session)throws HibernateException{
List result=session.createQuery(sql).list();
return result;
}
});
}
}
在spring 的appilcationContext.xml里CommonUserDao类配置如下
<bean id= "CommonUserDao "
class= "com.txForum.dao.CommonUserDao ">
<property name= "sessionFactory ">
<ref bean= "TXFSessionFactory " />
</property>
</bean>
问题就是在jsp页面中始终都得不到该对对像的实例
<%@ page language= "java " pageEncoding= "UTF-8 "%>
<%@ page import= "com.txForum.dao.* " %>
<%@ page import= "com.txForum.struts.action.* " %>
<%
SpringBaseBeanAction s=new SpringBaseBeanAction();
CommonUserDao c=(CommonUserDao)s.getBean( "CommonUserDao ");
%>
以下是报错内容
java.lang.NullPointerException
com.txForum.struts.action.SpringBaseBeanAction.getBean(SpringBaseBeanAction.java:20)
org.apache.jsp.web.test1_jsp._jspService(test1_jsp.java:61)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:384)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
请问为什么会得这空指针异常
我觉得是WebApplicationContext webapp对像根本就没有得到
[解决办法]
空指针 看一下test1_jsp.java:61对映的是什么?
[解决办法]
WebApplicationContext context =
(WebApplicationContext) config.getServletContext().getAttribute
(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
来得到WebApplicationContext的webapp对象
