java - JSP页面显示数据时出现java.lang.NumberFormatException

Question

我正在使用 Hibernate 和 Spring MVC。我试图从两个表中获取信息并将其显示在 jsp 页面中。这是我的表格:

表名称:学生

student_id    studentName
  1.           Jason Stathum

表名称:studentdetails

studentDetailsid   FatherName   MotherName    student_id
   1                 Mr.X          Mrs. Y        1

在我的 JSP 页面中，我尝试显示如下数据:

 Sl#   Student              Father     Mother
 1     Jason Stathum        Mr.X       Mrs.Y

当我运行应用程序以查看数据时，我收到以下错误消息:

HTTP 状态 500 - 处理 JSP 页面/WEB-INF/views/studentlist.jsp 第 29 行时发生异常根本原因java.lang.NumberFormatException:对于输入字符串:“FatherName” java.lang.NumberFormatException.forInputString(来源未知) java.lang.Integer.parseInt(来源未知) java.lang.Integer.parseInt(Unknown Source)...以及许多其他行...

我在下面包含了我的代码，你能告诉我我做错了什么吗？

非常感谢

实体:学生

@Entity
@Table(name = "student")
public class Student {

@Id 
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="student_id", nullable= false)
private Integer studentId;
private String studentName;

@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name="student_id", referencedColumnName="student_id")
private List<StudentDetails> studentDetails = new ArrayList<StudentDetails>();

// Getters and Setters

public Integer getStudentId() {
    return studentId;
}
public void setStudentId(Integer studentId) {
    this.studentId = studentId;
}
public String getStudentName() {
    return studentName;
}

public void setStudentName(String studentName) {
    this.studentName = studentName;
}
public List<StudentDetails> getStudentDetails() {
    return studentDetails;
}
public void setStudentDetails(List<StudentDetails> studentDetails) {
    this.studentDetails = studentDetails;
}

实体:学生详细信息

@Entity
@Table(name = "studentDetails")
public class StudentDetails {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Integer studentDetailsId;
private String FatherName;
private String MotherName;

// Getters and Setters

public Integer getStudentDetailsId() {
    return studentDetailsId;
}
public void setStudentDetailsId(Integer studentDetailsId) {
    this.studentDetailsId = studentDetailsId;
}
public String getFatherName() {
    return FatherName;
}
public void setFatherName(String fatherName) {
    FatherName = fatherName;
}
public String getMotherName() {
    return MotherName;
}
public void setMotherName(String motherName) {
    MotherName = motherName;
}

Controller

@RequestMapping(value="studentlist", method = RequestMethod.GET)
public String getRecords(Model map)
{       
    List<Student> student = studentService.getAll();
    map.addAttribute("student", student);
    return "studentlist";       
}

StudentDaoImpl

@Override
@SuppressWarnings("unchecked")
public List<Student> getAll() {
    return getSessionFactory().openSession().createQuery("FROM Student").list();
}

JSP页面:学生列表

<c:if test="${!empty student}">
<table class="studentTable">
<tr>
    <th>Sl#</th>
    <th>Name</th>
    <th>Father</th>
    <th>Mother</th>             

</tr>
<c:set var="count" value="0" scope="page" />
<c:forEach items="${student}" var="row">

    <c:set var="count" value="${count + 1}" scope="page"/>
    <tr>
        <td>${count}</td>
        <td>${row.studentName}</td>         
        <td>${row.studentDetails.FatherName}</td> <--- this is line 29
        <td>${row.studentDetails.MotherName}</td>
    </tr>
 </c:forEach>
</table>
</c:if>

Answer 1

问题是您试图引用 List 的属性对象。

${row.studentDetails} =List<StudentDetails>

JSTL 正在尝试转换 FatherName到一个数字，这样它就可以得到 List<StudentDetails> 中的索引.

要解决这个问题，你可以这样做 ${row.studentDetails[0].fatherName}或者你可以在 Student 中放入一个方法称为类似 getDefaultStudentData()这将返回第一个或“首选”学生详细信息对象，然后像 ${row.defaultStudentData.fatherName} 一样引用它。或者当然您可以更改输出以处理每个学生的多个学生详细信息☺