非常讨厌。不知道为什么会出现这个错误。在下面的代码中
NOTE:
if I only use <td>${user.id}</td> than its printing id properly but on ${user.username} property generating error. See below JSP page code.
If I use below code in JSP page like to test than I get all the objects and properties
<c:forEach var="user" items="${users}" varStatus="i">
<tr>
<td>${users[i.index]}</td>
</tr>
</c:forEach>
Result:
User[id=1,username=u1,password=p1,firstname=f1,lastname=l1,dob=2012-07-01,age=40]
User[id=2,username=u2,password=p2,firstname=f2,lastname=l2,dob=2012-07-02,age=39]
User[id=3,username=u3,password=p3,firstname=f3,lastname=l3,dob=2012-07-03,age=38]
错误：
09:49:49,047 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/crud_jsp_servlet_cdi_jdbc_tagfile].[jsp]] (http-localhost-127.0.0.1-8080-1) Servlet.service() for servlet jsp threw exception: javax.el.PropertyNotFoundException: The class 'com.myapp.dao.User' does not have the property 'username'.
at javax.el.BeanELResolver.getBeanProperty(BeanELResolver.java:661) [jboss-el-api_2.2_spec-1.0.0.Final.jar:1.0.0.Final]
at javax.el.BeanELResolver.getValue(BeanELResolver.java:290) [jboss-el-api_2.2_spec-1.0.0.Final.jar:1.0.0.Final]
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:175) [jboss-el-api_2.2_spec-1.0.0.Final.jar:1.0.0.Final]
at org.apache.el.parser.AstValue.getValue(AstValue.java:169) [jbossweb-7.0.13.Final.jar:]
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:189) [jbossweb-7.0.13.Final.jar:]
at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:935) [jbossweb-7.0.13.Final.jar:]
at org.apache.jsp.WEB_002dINF.admin.UserList_jsp._jspx_meth_c_005fforEach_005f0(UserList_jsp.java:137)
at org.apache.jsp.WEB_002dINF.admin.UserList_jsp.access$1(UserList_jsp.java:114)
at org.apache.jsp.WEB_002dINF.admin.UserList_jsp$Helper.invoke1(UserList_jsp.java:215)
at org.apache.jsp.WEB_002dINF.admin.UserList_jsp$Helper.invoke(UserList_jsp.java:240)
at org.apache.jsp.tag.web.layout_tag.doTag(layout_tag.java:120)
at org.apache.jsp.WEB_002dINF.admin.UserList_jsp._jspx_meth_tags_005flayout_005f0(UserList_jsp.java:96)
at org.apache.jsp.WEB_002dINF.admin.UserList_jsp._jspService(UserList_jsp.java:69)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) [jbossweb-7.0.13.Final.jar:]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) [jboss-servlet-api_3.0_spec-1.0.0.Final.jar:1.0.0.Final]
JSP页面：
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib prefix="tags" tagdir="/WEB-INF/tags"%>
<tags:layout path="${pageContext.request.contextPath}">
<jsp:attribute name="search">
<tags:search />
</jsp:attribute>
<jsp:body>
<div class="mainDiv">
<table class="table table-striped table-bordered table-condensed">
<thead>
<tr>
<th>Id</th>
<th>UserName</th>
<th>Password</th>
<th>FirstName</th>
<th>LastName</th>
<th>Date of Birth</th>
<th>Age</th>
<th>Actions</th>
</tr>
</thead>
<tbody>
<c:forEach var="user" items="${users}">
<tr>
<td>${user.id}</td>
<td>${user.username}</td>
<td>${user.password}</td>
<td>${user.firstname}</td>
<td>${user.lastname}</td>
<td>${user.dob}</td>
<td>${user.age}</td>
<td><a href="#"><i class="icon-edit"></i></a> <a href="#"><i
class="icon-trash"></i></a></td>
</tr>
</c:forEach>
</tbody>
</table>
</div>
</jsp:body>
</tags:layout>
的 User.java 的
package com.myapp.dao;
import java.sql.Date;
public class User {
private Long id;
private String username;
private String password;
private String firstname;
private String lastname;
private Date dob;
private int age;
public User(){
};
public User(Long id, String username, String password, String firstname, String lastname, Date dob, int age){
this.id = id;
this.username = username;
this.password = password;
this.firstname = firstname;
this.lastname = lastname;
this.dob = dob;
this.age = age;
}
public Long getId(){
return id;
}
public void setId(Long id){
this.id = id;
}
public String getUserName(){
return username;
}
public void setUserName(String username){
this.username = username;
}
public String getPassword(){
return password;
}
public void setPassword(String password){
this.password = password;
}
public String getFirstName(){
return firstname;
}
public void setFirstName(String firstname){
this.firstname = firstname;
}
public String getLastName(){
return lastname;
}
public void setLastName(String lastname){
this.lastname = lastname;
}
public Date getDob(){
return dob;
}
public void setDob(Date dob){
this.dob = dob;
}
public int getAge(){
return age;
}
public void setAge(int age){
this.age = age;
}
public String getFullName(){
return this.firstname + " " + this.lastname;
}
}
的 Selvlet： 的
List<User> users = null;
userDAO = new UserDAOJDBC();
users = userDAO.listUsers();
request.setAttribute("users", users);
String path = "/WEB-INF/admin/UserList.jsp";
getServletContext().getRequestDispatcher(path).forward(request, response);
答案 0 :(得分：5)
案例对Java Bean属性很重要。在EL中，您尝试访问属性username，但在bean中，您有getUserName/setUserName。请改用getUsername/setUsername（小写'n'）。