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最后更新时间：2007-05-11
有一个Employee类：
public class Employee implements java.io.Serializable {
private int id;
private String name;
private Department department;
public Employee() {
}
public int getId() {
return this.id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public Department getDepartment() {
return this.department;
}
public void setDepartment(Department department) {
this.department = department;
}
}
每个Employee属于一个Department，Department类如下： public class Department implements java.io.Serializable {
private int id;
private String name;
public Department() {
}
public int getId() {
return this.id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
}
我为这两个类分别写了相应的DAO（EmployeeDao、DepartmentDao）、Action（EmployeeAction、DepartmentAction）并实现了相应的crud操作。其中在DepartmentDao中实现了findAll方法如下： public List findAll() {
String sql = " FROM Department ORDER BY id";
return this.getHibernateTemplate().find(sql);
}
DepartmentDao在applicationContext.xml中已经配置为一个bean： <?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd"> <beans> <!-- DAO --> <bean id="departmentDao" class="cn.net.cogent.powermedical.sysinfo.dao.DepartmentDao"> <property name="sessionFactory"> <ref bean="sessionFactory"/> </property> </bean> <!-- 其它配置略 --> </beans> 打算在编辑一个Employee时允许用户从已有的Department列表中选择一个指定给department属性，jsp页面代码如下： <%@page pageEncoding="GBK" contentType="text/html; charset=GBK" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>编辑员工</title>
</head>
<body>
<s:form name="editForm" action="save" validate="true">
<s:textfield label="编号" name="employee.id" readonly="true"/>
<s:textfield label="姓名" name="employee.name"/>
<s:if test="null == employee">
<s:hidden name="employee.id" value="%{id}"/>
</s:if>
<s:else>
<s:hidden name="employee.id" />
</s:else>
<s:select label="部门" name="employee.department" value="employee.department.id"
list="#departmentDao.findAll()" listKey="id" listValue="name" />
<s:submit value="保存" />
</s:form>
</body>
</html>
但在访问该页面的时候报如下错误： WARN - Caught an exception while evaluating expression '#departmentDao.findAll()' against value stack java.lang.NullPointerException: target is null for method findAll at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:848) 这是怎么回事呢？我应该怎样配置才能在jsp页面上显示部门列表，并允许用户选择一个呢？ 声明：JavaEye文章版权属于作者，受法律保护。没有作者书面许可不得转载。
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最后更新时间：2007-05-11
应该是这样的形式得到部门列表：
其中getAllDepartment是个action,需要在jsp页面和xml文件里申明 departmentList是action里的一个属性，需要有get取值函数 在action里面要干的事是给departmentList付值
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最后更新时间：2007-05-12
to 温柔一刀:
按照你的建议进行了修改，jsp页面代码为： <%@page pageEncoding="GBK" contentType="text/html; charset=GBK" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>编辑员工</title>
</head>
<body>
<s:form name="editForm" action="save" validate="true">
<s:textfield label="编号" name="employee.id" readonly="true"/>
<s:textfield label="姓名" name="employee.name"/>
<s:if test="null == employee">
<s:hidden name="employee.id" value="%{id}"/>
</s:if>
<s:else>
<s:hidden name="employee.id" />
</s:else>
<s:select label="部门" name="employee.department" value="employee.department.id"
list="#departmentAction.departments" listKey="id" listValue="name" />
<s:submit value="保存" />
</s:form>
</body>
</html>
其中departmentAction已经在applicationContext.xml中配置为一个bean，与departments属性相关的代码如下： public class DepartmentAction extends ActionSupport {
private List departments;
public List getDepartments() {
if (null == departments)
departments = departmentDao.findAll();
return this.departments;
}
}
访问页面时报如下错误： 2007-5-12 8:53:43 org.apache.catalina.core.ApplicationDispatcher invoke
严重: Servlet.service() for servlet jsp threw exception
tag 'select', field 'list', name 'employee.department': The requested list key '#departmentAction.departments' could not be resolved as a collection/array/map/enumeration/iterator type. Example: people or people.{name} - [unknown location]
at org.apache.struts2.components.Component.fieldError(Component.java:231)
departmentAction的departments被声明为List类型，为什么还会出错呢？ |
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最后更新时间：2007-05-12
你那样做是不对的
在jsp页面要有这样的申明： <ww:action name="departmentAction" id="departmentAction"/> name是指在xml里面配置的action，id是这样引用需要的#departmentAction 你的action大概应该是这样子的：
public class DepartmentAction extends ActionSupport {
private List departments;
public List getDepartments() {
return this.departments;
}
public String getAllDepartment() {
departments = departmentDao.findAll();
return null;
}
}
xml配置文件大概是这样子的： <action name="departmentAction" class="xxx.DepartmentAction " method="getAllDepartment"> </action> |
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最后更新时间：2007-05-12
谢谢 温柔一刀:
确实是忘了在jsp页面上声明departmentAction了。添加了声明后就正常了 |
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