Struts2:关于向对象传递数据的问题！

Question

本人的开发环境是：Tomcat7+Struts2+JDK1.6+myeclipse8.6。问题如下，在页面中点击“部门管理”，根据：(第24行）String departmentname=Change.toChinese(getDepartment().getDepartmentname()!=null?getDepartment().getDepartmentname():request.getParameter("departmentname"));判断SQL的查询条件。
可每次点击后总会抛出NULL错误，Tomcat提示的错误是：HTTP Status 500 -
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NullPointerException
com.pingpingme.action.DepartmentAction.list(DepartmentAction.java:24)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)DepartmentAction.java的代码如下：package com.pingpingme.action;
import java.util.ArrayList;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import com.opensymphony.xwork2.ActionSupport;
import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.ServletActionContext;
import com.pingpingme.dao.DepartmentDao;
import com.pingpingme.actionform.Department;
import com.pingpingme.tools.Change;
public class DepartmentAction extends ActionSupport {
DepartmentDao departmentdao=new DepartmentDao();
private Department department;
public void setDepartment(Department department) {
this.department=department;
}
public Department getDepartment() {
return department;
}
//查询所有部门
public String list() throws Exception {
ArrayList departmentList=new ArrayList();
HttpServletRequest request=ServletActionContext.getRequest();
String departmentname=Change.toChinese(getDepartment().getDepartmentname()!=null?getDepartment().getDepartmentname():request.getParameter("departmentname"));
if(departmentname==null || departmentname.equals("")) departmentname="all";
String sql="";
if(departmentname.equals("all")) {
sql="select * from tb_department";
}else {
sql="select * from tb_department where departmentname='"+departmentname+"'";
}
String currentpage=request.getParameter("i");
if(currentpage==null || currentpage.equals("")) currentpage="0";
departmentList=departmentdao.getAllDepartment(sql);
int numrs=departmentList.size();
int maxpage=departmentList.size();
if(maxpage%12==0) {
maxpage=maxpage/12;
}else {
maxpage=maxpage/12+1;
}
request.setAttribute("currentpage",currentpage);
request.setAttribute("maxpage", String.valueOf(maxpage));
request.setAttribute("numrs", String.valueOf(numrs));
request.setAttribute("departmentList", departmentList);
request.setAttribute("pagepath", "/Departmentlist.action");
request.setAttribute("departmentname", departmentname);
return "list";
}
}
烦请各位看看，为什么会抛出这个错误，如何解决，谢谢！

Answer 1

department可能是null不知道你是如何传值的！

Answer 2

点击“部门管理”是查询所有的部门信息然，后进入到查询结果页面，查询结果页面是：一个简单的查询条件（根据部门名称查询）加上查询到的资料。JSP页面的代码如下：
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%@ page import="com.pingpingme.actionform.Department" %>
<%@ page import="java.util.ArrayList" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<%
  String pagepath=(String)request.getAttribute("pagepath");
  if(pagepath==null) pagepath="";
  ArrayList departmentList=(ArrayList)request.getAttribute("departmentList");
  int currentpage=Integer.parseInt((String)request.getAttribute("currentpage"));
  int maxpage=Integer.parseInt((String)request.getAttribute("maxpage"));
  int numrs=Integer.parseInt((String)request.getAttribute("numrs"));
  int start=currentpage*12;               //开始条数
  int over=(currentpage+1)*12;            //结束条数
  int count=numrs-over;                   //还剩多少条记录
  if(count<0) over=numrs;
 %>
<div class="page">
  <div class="pageHeader">
    <s:form id="" theme="simple" onsubmit="return navTabSearch(this);" action="Departmentlist" method="post">
      <div class="searchBar">
        <ul class="searchContent">
          <li> <label>部门名称：</label> <s:textfield size="16"></s:textfield> </li>
        </ul>
        <div class="subBar">
          <ul>
            <li><div class="buttonActive"> <div class="buttonContent"> <button type="submit">检索</button> </div> </div></li>
            <li>
              <a class="button" href="" target="dialog" rel="rel_pagel" title="查询框"> <span>高级检索</span> </a>
            </li>
          </ul>
        </div>
      </div>
    </s:form>
  </div>
  <div class="pageContent">
    <div class="panelBar">
      <ul class="toolBar">
        <li><a class="add" href="#" target="navTab"><span>添加</span></a></li>
        <li><a class="delete" href="#" target="navTabTodo" title="确定要删除吗？"><span>删除</span></a></li>
        <li><a class="edit" href="#" target="navTab"><span>修改</span></a></li>
      </ul>
    </div>
    <table class="table" layouth="138">
      <thead>
        <tr>
  <th style="width:120px;">公司编号</th>
  <th style="width:140px;">部门编号</th>
  <th style="width:100px;">部门名称</th>
  <th style="width:150px;">部门信息</th>
  <th style="width:50px;">上级部门</th>
  <th style="width:75px;">显示顺序</th>
  <th style="width:60px;">备注</th>
        </tr>
      </thead>
      <tbody>
        <%
         for(int i=start;i<over;i++) {
           Department department=(Department)departmentList.get(i);
        %>
        <tr>
          <td> <%=department.getCompanycode() %> </td>
          <td> <%=department.getDepartmentcode() %> </td>
          <td> <%=department.getDepartmentname() %> </td>
          <td> <%=department.getDepartmentdescription() %></td>
          <td> <%=department.getParentdepartment() %> </td>
          <td> <%=department.getIndexorder() %> </td>
          <td> <%=department.getRe() %> </td>
        </tr>
        <%
         }
        %>
      </tbody>
    </table>
    <div class="panelBar">
      <div class="pages">
        <span>共有${maxpage}</span><span>页，总共${numrs}条，</span><span>当前为第${currentpage+1}页</span>
      </div>
      <div class="pages" >
       <s:form theme="simple" onsubmit="return navTabSearch(this);" action="Departmentlist" title="部门管理">
        <%if((currentpage+1)==1) {%>首页<%}else { %><a href="<%=request.getContextPath()%><%=pagepath%>?i=0" target="navTab" title="部门管理">[首页]</a><%} %>&nbsp;
        <%if(maxpage<=(currentpage+1)) {%>尾页<%}else{ %><a href="<%=request.getContextPath()%><%=pagepath%>?i=<%=maxpage-1 %>" target="navTab" title="部门管理">[尾页]</a><%} %>&nbsp;
        <select name="i">
          <%
            for(int j=0;j<maxpage;j++) {  
          %>
          <option value="<%=j%>"><%=j+1 %></option>
          <%} %>
        </select>
        <input type="submit" name="Submit" value="查询">&nbsp;&nbsp;
        <%if((currentpage+1)==1){%>上一页<%}else{%><a href="<%=request.getContextPath()%><%=pagepath%>?i=<%=currentpage-1 %>" target="navTab" title="部门管理">上一页</a><%} %>&nbsp;
        <%if(maxpage<(currentpage+1)){%>下一页<%}else{ %><a href="<%=request.getContextPath()%><%=pagepath%>?i=<%=currentpage+1 %>" target="navTab" title="部门管理">下一页</a><%} %>&nbsp;
       </s:form>
      </div>
    </div>
  </div>
</div>

Answer 3

一般这样写比较好null != getDepartment().getDepartmentname()

Answer 4

你这里的 getDepartment() 一定是空值  
所以你还要先判断 
null!=getDepartment()应该是下面这样写
(null!=getDepartment())&&(null != getDepartment().getDepartmentname())

Answer 5

department = null了。