Question

我正在开展一个大学项目，存储各种学习资料的链接。我的数据库中有一个指向文本教程的链接列表，项目的文件如下：

TextTutorialController.java：

package io.spring.learn.web;

import java.util.List;

import javax.inject.Inject;

import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import io.spring.learn.proc.TextTutorial;
import io.spring.learn.proc.TextTutorialService;

@Controller
@RequestMapping("/textTutorials")
public class TextTutorialController {

    @Inject
    TextTutorialService service;

    @RequestMapping(value = "/listOfTextTutorials", method = RequestMethod.GET)
    public String showList(ModelMap model) {
        List<TextTutorial> listOfTextTutorials = service.findAll();
        model.addAttribute("textTutorialList", listOfTextTutorials);
        return "listOfTextTutorials";
    }

}

listOfTextTutorials.jsp：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="s" uri="http://www.springframework.org/tags"%>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>List of Text Tutorials</title>
</head>
<body>
    <h1>List of Text Tutorials on Spring:</h1>
    <table>
        <tr>
            <th>ID</th>
            <th>Name</th>
            <th>URL</th>
            <th>Alexa Global Rank</th>
            <th>Total Chapters</th>
            <th>% Completed</th>
        </tr>
        <c:forEach var="textTutorial" items="${textTutorialList}">
            <tr>
                <td><c:out value="${textTutorial.id}" /></td>
                <td><c:out value="${textTutorial.name}" /></td>
                <td><c:out value="${textTutorial.url}" /></td>
                <td><c:out value="${textTutorial.alexaGlobalRank}" /></td>
                <td><c:out value="${textTutorial.totalChapters}" /></td>
                <td><c:out value="${textTutorial.percentCompleted}" /></td>
            </tr>
        </c:forEach>
    </table>
</body>
</html>

的index.jsp：

<!DOCTYPE html>

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>

<html>
    <head>
        <meta charset="utf-8">
        <title>Welcome</title>
    </head> 
    <body>
        <a href="textTutorials/listOfTextTutorials.html">List of Text Tutorials on Spring</a>
    </body>
</html>

在Tomcat上运行应用程序后，控制台显示数据库连接正常，甚至查询了一些SELECT语句：

[EL Info]: 2016-06-29 03:29:17.721--ServerSession(2113257970)--EclipseLink, version: Eclipse Persistence Services - 2.5.0.v20130507-3faac2b
[EL Info]: connection: 2016-06-29 03:29:18.265--ServerSession(2113257970)--file:/Users/AgentDen/Documents/Java/MyProjectSpringMVC/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/LearnSpringMVC/WEB-INF/classes/_LearnSpring login successful
[EL Fine]: sql: 2016-06-29 03:29:18.314--ServerSession(2113257970)--Connection(302754878)--SELECT ID FROM books WHERE ID <> ID
[EL Fine]: sql: 2016-06-29 03:29:18.842--ServerSession(2113257970)--Connection(500719466)--SELECT ID FROM CLASSROOM WHERE ID <> ID
[EL Fine]: sql: 2016-06-29 03:29:18.886--ServerSession(2113257970)--Connection(1612903660)--SELECT ID FROM general_articles WHERE ID <> ID
[EL Fine]: sql: 2016-06-29 03:29:18.905--ServerSession(2113257970)--Connection(250314644)--SELECT ID FROM online_courses WHERE ID <> ID
[EL Fine]: sql: 2016-06-29 03:29:18.922--ServerSession(2113257970)--Connection(474813894)--SELECT ID FROM text_tutorials WHERE ID <> ID
[EL Fine]: sql: 2016-06-29 03:29:18.936--ServerSession(2113257970)--Connection(1688125903)--SELECT ID FROM youtube_tutorials WHERE ID <> ID
[EL Fine]: sql: 2016-06-29 03:29:19.619--ServerSession(2113257970)--Connection(585968463)--SELECT ID, alexa_global_rank, chapters_studied, date_finished, date_started, days_spent, LANGUAGE, LEVEL, NAME, percent_completed, personal_rating, total_chapters, URL FROM text_tutorials

但是我的jsp中显示的所有内容都只是html标题和表头，但是模型中没有显示数据：

List of Text Tutorials on Spring:

ID  Name    URL Alexa Global Rank   Total Chapters  % Completed

JSTL包含在pom.xml中：

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>jstl</artifactId>
    <version>1.2</version>
</dependency>

我在这里读过类似的问题，但似乎没有一个特定于我的案例。我已经非常绝望了，所以任何建议都会受到高度赞赏！

UPD。以下是服务的findAll（）方法的实现：

    package io.spring.learn.proc;

    import java.util.List;

    import javax.persistence.EntityManager;
    import javax.persistence.NoResultException;
    import javax.persistence.PersistenceContext;
    import javax.persistence.TypedQuery;

    import org.springframework.stereotype.Repository;

    @Repository
    public class TextTutorialDaoImpl implements TextTutorialDao {

        @PersistenceContext
        private EntityManager em;

        @Override
        public List<TextTutorial> findAll() {
            TypedQuery<TextTutorial> query = em.createQuery("Select txt from TextTutorial txt", TextTutorial.class);
            return query.getResultList();
        }

    ...

}

和服务实施：

package io.spring.learn.proc;

import java.util.List;

import javax.inject.Named;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.transaction.annotation.Transactional;

@Named
public class TextTutorialServiceImpl implements TextTutorialService {

    @Inject
    private TextTutorialDao txtDao;

    @Override
    public List<TextTutorial> findAll() {
        return txtDao.findAll();
    }

...

}

Answer 1

您的代码看起来不错。我唯一可以怀疑的是你的服务 - 我相信它会返回一个空列表。在将其添加到模型图之前，您可以打印出列表的大小吗？

public String showList(ModelMap model) {
    List<TextTutorial> listOfTextTutorials = service.findAll();
    System.out.println(listOfTextTutorials.size()); // <-- This line.
    model.addAttribute("textTutorialList", listOfTextTutorials);
    return "listOfTextTutorials";
}

Answer 2

如何将控制器方法更改为此？

@RequestMapping(value = "/listOfTextTutorials", method = RequestMethod.GET)
public ModelAndView showList(ModelMap model) {
    List<TextTutorial> listOfTextTutorials = service.findAll();
    return new ModelAndView("listOfTextTutorials", "textTutorialList", listOfTextTutorials);;
}

对于旧的JSP 1.2描述符，您必须手动启用EL。在JSP中添加以下代码。

<%@ page isELIgnored="false" %>

Answer 3

好的，感谢@Nguyen Tuan Anh的建议，检查从服务返回的List的大小我开始挖掘并意识到Spring与DB的连接在某种程度上已经被破坏了。将application-config.xml中的数据库网址从相对位置更改为绝对值已解决了该问题，但我仍然无法确定为什么相对路径返回零结果。

Spring MVC不在jsp中显示DB数据

3 个答案: