Я начинающий, поэтому сильно не пинайте.  В общем, ситуация такова: есть база данных, есть бин, который через JPA и hibernate работает с полями этой БД, есть манагер, который управляет бинами и есть JSP страничка, куда надо значение из БД вывести. Делаю так: Question.java| Код |
@Entity
@Table(name = "QUESTIONS")
@NamedQueries({
@NamedQuery(
name = "getQuestions",
query = "select q from Question q"
)
})
public class Question implements Serializable {
@Id
@Column(name = "ID")
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;
@Column(name = "QUESTION")
private String value;
@Column(name = "ANSWER_ID")
private int rightAnswerId;
public Question() {
}
public Question(int id, String question) {
this.id = id;
this.value = question;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getValue() {
return value;
}
public void setValue(String question) {
this.value = question;
}
public int getRightAnswerId() {
return rightAnswerId;
}
public void setRightAnswerId(int rightAnswerId) {
this.rightAnswerId = rightAnswerId;
}
}
|
| Код |
public class QuestionManager implements Manager {
@PersistenceUnit(unitName = "TestingList")
EntityManager entityManager;
public void init() {
entityManager = Main.getInstance().getEntityManager();
}
public Question getQuestion(int id) {
return entityManager.find(Question.class, id);
}
public ArrayList<Question> getQuestions() {
Query query = entityManager.createNamedQuery("getQuestions");
return (ArrayList<Question>) query.getResultList();
}
public void destroy() {
entityManager.clear();
}
}
|
| Код |
<html>
<head>
<title>Testing List</title>
</head>
<body>
[<a href="manage_list.jsp">Manage List</a>]
</body>
</html>
|
| Код |
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib uri="http://java.sun.com/jstl/core" prefix="c" %>
<jsp:useBean id="question" class="ru.testinglist.bean.Question"/>
<jsp:useBean id="questionManager" class="ru.testinglist.manager.QuestionManager"/>
<html>
<c:import url="index.html"/>
<body>
<table border="1" align="center" width="100%">
<tr>
<td align="center" width="80%"><strong>Question</strong></td>
<td align="center"><strong>Action</strong></td>
</tr>
<%--<c:forEach var="question" items="${questionManager.questions}">--%>
<tr>
<td><c:out value="${questionManager.questions.question.value}"/></td>
<td>
<button>Edit</button>
<button>Delete</button>
</td>
</tr>
<%--</c:forEach>--%>
</table>
</body>
</html>
|
| Код |
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
</web-app>
|
В итоге, если я запускаю это всё как обычное десктопное приложение, то все записи из БД без проблем в консоль выводятся, а когда запускаю как вэб, то при переходе на страничку manage_list.jsp в браузере отображается такая ошибка: | Код |
HTTP Status 500 -
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: An exception occurred processing JSP page /manage_list.jsp at line 25
22:
23: <%--<c:forEach var="question" items="${questionManager.questions}">--%>
24: <tr>
25: <td><c:out value="${questionManager.questions.question.value}"/></td>
26: <td>
27: <button>Edit</button>
28: <button>Delete</button>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:524)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:417)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause
javax.servlet.ServletException: javax.servlet.jsp.JspException: An error occurred while evaluating custom action attribute "value" with value "${questionManager.questions.question.value}": An error occurred while getting property "questions" from an instance of class ru.testinglist.manager.QuestionManager (java.lang.NullPointerException)
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:846)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:779)
org.apache.jsp.manage_005flist_jsp._jspService(manage_005flist_jsp.java:120)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause
java.lang.NullPointerException
ru.testinglist.manager.QuestionManager.getQuestions(QuestionManager.java:29)
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)
org.apache.taglibs.standard.lang.jstl.ArraySuffix.evaluate(ArraySuffix.java:278)
org.apache.taglibs.standard.lang.jstl.ComplexValue.evaluate(ComplexValue.java:107)
org.apache.taglibs.standard.lang.jstl.ELEvaluator.evaluate(ELEvaluator.java:204)
org.apache.taglibs.standard.lang.jstl.ELEvaluator.evaluate(ELEvaluator.java:163)
org.apache.taglibs.standard.lang.jstl.Evaluator.evaluate(Evaluator.java:101)
org.apache.taglibs.standard.lang.jstl.Evaluator.evaluate(Evaluator.java:129)
org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager.evaluate(ExpressionEvaluatorManager.java:75)
org.apache.taglibs.standard.tag.el.core.ExpressionUtil.evalNotNull(ExpressionUtil.java:48)
org.apache.taglibs.standard.tag.el.core.OutTag.evaluateExpressions(OutTag.java:99)
org.apache.taglibs.standard.tag.el.core.OutTag.doStartTag(OutTag.java:57)
org.apache.jsp.manage_005flist_jsp._jspx_meth_c_005fout_005f0(manage_005flist_jsp.java:164)
org.apache.jsp.manage_005flist_jsp._jspService(manage_005flist_jsp.java:100)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.14 logs.
Apache Tomcat/6.0.14
|
Объекты QuestionManager и Question создаются, но вот значения получить не удаётся...  |
Вывод данных из БД в JSP используя JSTL (ч. 2), Помогите найти ошибку! 
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