javax.el.ELException:读取Person类型的[name]时出错

Question

我使用hibenate和springmvc编写了一个程序。但当我执行编辑函数时，它会给我带来错误。

Type Exception Report
Message An exception occurred processing JSP page [/WEB-INF/views/person.jsp] at line [24]
Description The server encountered an unexpected condition that prevented it from fulfilling the request.
Exception
org.apache.jasper.JasperException: An exception occurred processing JSP page [/WEB-INF/views/person.jsp] at line [24]
21: 
22: <form:form action="${addAction}" commandName="person">
23:     <table>
24:         <c:if test="${!empty person.name}">
25:             <tr>
26:                 <td>
27:                     <form:label path="id">

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:584)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:481)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1257)
org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1037)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:980)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
Root Cause
javax.el.ELException: Error reading [name] on type [com.baotrung.entity.Person_$$_jvsta7c_0]
javax.el.BeanELResolver.getValue(BeanELResolver.java:98)
org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:110)
org.apache.el.parser.AstValue.getValue(AstValue.java:169)
org.apache.el.parser.AstEmpty.getValue(AstEmpty.java:46)
org.apache.el.parser.AstNot.getValue(AstNot.java:43)
org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:944)
org.apache.jsp.WEB_002dINF.views.person_jsp._jspx_meth_c_005fif_005f0(person_jsp.java:325)
org.apache.jsp.WEB_002dINF.views.person_jsp._jspx_meth_form_005fform_005f0(person_jsp.java:247)
org.apache.jsp.WEB_002dINF.views.person_jsp._jspService(person_jsp.java:170)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1257)
org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1037)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:980)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
Root Cause
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:147)
org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:260)
org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:68)
com.baotrung.entity.Person_$$_jvsta7c_0.getName(Person_$$_jvsta7c_0.java)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:498)
javax.el.BeanELResolver.getValue(BeanELResolver.java:94)
org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:110)
org.apache.el.parser.AstValue.getValue(AstValue.java:169)
org.apache.el.parser.AstEmpty.getValue(AstEmpty.java:46)
org.apache.el.parser.AstNot.getValue(AstNot.java:43)
org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:944)
org.apache.jsp.WEB_002dINF.views.person_jsp._jspx_meth_c_005fif_005f0(person_jsp.java:325)
org.apache.jsp.WEB_002dINF.views.person_jsp._jspx_meth_form_005fform_005f0(person_jsp.java:247)
org.apache.jsp.WEB_002dINF.views.person_jsp._jspService(person_jsp.java:170)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1257)
org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1037)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:980)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

个人实体

package com.baotrung.entity;
import javax.persistence.*;
@Entity
@Table(name = "PERSON")
public class Person {
@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
private String country;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
@Override
public String toString() {
return "Person{" +
"id=" + id +
", name='" + name + ''' +
", country='" + country + ''' +
'}';
}
}

控制器类

package com.baotrung.controller;
import com.baotrung.entity.Person;
import com.baotrung.services.PersonService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@Controller
public class PersonController {
private PersonService personService;
@Autowired(required = true)
public void setPersonService(PersonService personService) {
this.personService = personService;
}
@RequestMapping(value ="/persons",method = RequestMethod.GET)
public String listPersons(Model model){
model.addAttribute("person",new Person());
model.addAttribute("listPersons",this.personService.listPerson());
return "person";
}
@RequestMapping(value ="/person/add",method = RequestMethod.POST)
public String addPerson(@ModelAttribute("person")Person p){
if(p.getId()==0){
this.personService.addPerson(p);
}else{
this.personService.updatePerson(p);
}
return "redirect:/persons";
}
@RequestMapping("/edit/{id}")
public String editPerson(@PathVariable("id")int id,Model model){
model.addAttribute("person",this.personService.getPersonById(id));
model.addAttribute("listPersons",this.personService.listPerson());
return "person";
}
@RequestMapping("/remove/{id}")
public String removePerson(@PathVariable("id")int id){
this.personService.removePerson(id);
return "redirect:/persons";
}
}

个人DAO

package com.baotrung.dao;
import com.baotrung.entity.Person;
import org.hibernate.Session;
import org.hibernate.SessionFactory;

import java.util.List;

public class PersonDAOImpl implements PersonDAO {
private SessionFactory sessionFactory;
public void setSessionFactory(SessionFactory sessionFactory) {
this.sessionFactory = sessionFactory;
}
@Override
public void addPerson(Person p) {
Session session = this.sessionFactory.getCurrentSession();
session.persist(p);
}
@Override
public void updatePerson(Person p) {
Session session = this.sessionFactory.getCurrentSession();
session.update(p);
}
@SuppressWarnings("unchecked")
@Override
public List<Person> listPerson() {
Session session = this.sessionFactory.getCurrentSession();
List<Person> personList = session.createQuery("from Person").list();
return personList;
}
@Override
public Person getPersonById(int id) {
Session session = this.sessionFactory.getCurrentSession();
Person p = (Person) session.load(Person.class,new Integer(id));
return p;
}
@Override
public void removePerson(int id) {
Session session = this.sessionFactory.getCurrentSession();
Person p = (Person)session.load(Person.class,new Integer(id));
if(null!=p){
session.delete(p);
}
}
}

个人服务

package com.baotrung.services;
import com.baotrung.dao.PersonDAO;
import com.baotrung.entity.Person;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;
public class PersonServiceImpl implements PersonService {
private PersonDAO personDAO;
public void setPersonDAO(PersonDAO personDAO) {
this.personDAO = personDAO;
}
@Override
@Transactional
public void addPerson(Person p) {
this.personDAO.addPerson(p);
}

@Override
@Transactional
public void updatePerson(Person p) {
this.personDAO.updatePerson(p);
}
@Override
@Transactional
public List<Person> listPerson() {
return this.personDAO.listPerson();
}
@Override
@Transactional
public Person getPersonById(int id) {
return this.personDAO.getPersonById(id);
}
@Override
@Transactional
public void removePerson(int id) {
this.personDAO.removePerson(id);
}
}

Jsp页面：Person.Jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://www.springframework.org/tags" prefix="spring" %>
<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form" %>
<%@ page session="false" %>
<html>
<head>
<title>Person Page</title>
<style type="text/css">
.tg  {border-collapse:collapse;border-spacing:0;border-color:#ccc;}
.tg td{font-family:Arial, sans-serif;font-size:14px;padding:10px 5px;border-style:solid;border-width:1px;overflow:hidden;word-break:normal;border-color:#ccc;color:#333;background-color:#fff;}
.tg th{font-family:Arial, sans-serif;font-size:14px;font-weight:normal;padding:10px 5px;border-style:solid;border-width:1px;overflow:hidden;word-break:normal;border-color:#ccc;color:#333;background-color:#f0f0f0;}
.tg .tg-4eph{background-color:#f9f9f9}
</style>
</head>
<body>
<h1>
Add a Person
</h1>
<c:url var="addAction" value="/person/add" ></c:url>
<form:form action="${addAction}" commandName="person">
<table>
<c:if test="${!empty person.name}">
<tr>
<td>
<form:label path="id">
<spring:message text="ID"/>
</form:label>
</td>
<td>
<form:input path="id" readonly="true" size="8"  disabled="true" />
<form:hidden path="id" />
</td>
</tr>
</c:if>
<tr>
<td>
<form:label path="name">
<spring:message text="Name"/>
</form:label>
</td>
<td>
<form:input path="name" />
</td>
</tr>
<tr>
<td>
<form:label path="country">
<spring:message text="Country"/>
</form:label>
</td>
<td>
<form:input path="country" />
</td>
</tr>
<tr>
<td colspan="2">
<c:if test="${!empty person.name}">
<input type="submit"
value="<spring:message text="Edit Person"/>" />
</c:if>
<c:if test="${empty person.name}">
<input type="submit"
value="<spring:message text="Add Person"/>" />
</c:if>
</td>
</tr>
</table>
</form:form>
<br>
<h3>Persons List</h3>
<c:if test="${!empty listPersons}">
<table class="tg">
<tr>
<th width="80">Person ID</th>
<th width="120">Person Name</th>
<th width="120">Person Country</th>
<th width="60">Edit</th>
<th width="60">Delete</th>
</tr>
<c:forEach items="${listPersons}" var="person">
<tr>
<td>${person.id}</td>
<td>${person.name}</td>
<td>${person.country}</td>
<td><a href="<c:url value='/edit/${person.id}' />" >Edit</a></td>
<td><a href="<c:url value='/remove/${person.id}' />" >Delete</a></td>
</tr>
</c:forEach>
</table>
</c:if>
</body>
</html>

我不明白为什么spring找不到属性person.name。我在person实体中设置了setter和getter。请帮帮我。谢谢

Answer 1

异常不是发生在Person类上(顺便说一下，它看起来不错)，而是发生在为类创建的Hibernate的proxy对象中，请注意奇怪的类名Person_$$_jvsta7c_0。

发生这种情况是因为当您调用edit操作时，会调用调用的方法getPersonById

Person p = (Person) session.load(Person.class,new Integer(id));

session.load()创建一个值未初始化的proxy对象。

关于session.load()和session.get()(来源)的一些信息

session.load()

• 它将始终返回一个"代理"(Hibernate术语)，而不会访问数据库。在Hibernate中，proxy是一个具有给定标识符的对象值，其属性尚未初始化，只是看起来像临时假对象
• 如果找不到行，它将抛出一个ObjectNotFoundException

session.get()

• 它总是访问数据库并返回真实的对象，一个表示数据库行的对象，而不是代理
• 如果未找到行，则返回null

简而言之，尝试将session.load()更改为session.get()