Question

当我使用控制器在studentbyid.jsp页面上显示数据时，然后引发错误->发生意外错误（类型=内部服务器错误，状态= 500）。在类型[java.lang.String]

上找不到属性[id]


@Controller
public class StudentController {

    @Autowired
    private StudentService studentService  ;

    @GetMapping(value = "/students")
    public  String index(ModelMap modelMap){
        modelMap.put("students" , studentService.findAll());
        System.out.println(" Student for id =" + studentService.findAll());
        return "index" ;
    }

    @GetMapping(value = "/studentid")
    public String studentdetailed(@RequestParam("id") int id , ModelMap modelMap){

        modelMap.put("students" , studentService.findById(id));
        System.out.println(" Student for id =" + studentService.findById(id));

        return "studentbyid" ;
    }



    @GetMapping(value = "/student")
    public String databyid(){
        return "student" ;
    }
}


public interface StudentService {

    public Iterable<Student> findAll() ;
    public Optional<Student> findById(int id) ;
}


@Transactional
@Service("studentService")
public class StudentServiceImpl implements StudentService {

    @Autowired
    private StudentRepository studentRepository ;

    @Override
    public Iterable<Student> findAll() {
        return studentRepository.findAll();
    }

    public Optional<Student> findById(int id) {
        return studentRepository.findById(id);
    }
}


<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Student Data</title>
</head>
<body>

   <c:forEach var="student" items="students">
        <c:out value="${student.id}"/>
        <c:out value="${student.firstName}"/>
        <c:out value="${student.lastName}"/>
        <c:out value="${student.branch}"/>
        <c:out value="${student.year}"/>
        <c:out value="${student.mobileNumber}"/>
   </c:forEach>

</body>
</html>


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

    @Id
    @Column(name="id")
    private int id ;

    @Column(name="first_name")
    private String firstName ;

    @Column(name="last_name")
    private String lastName ;

    @Column(name="branch")
    private String branch ;

    @Column(name="year")
    private int  year ;

    @Column(name="mobile_number")
    private String mobileNumber ;

    public Student() {
    }

    public Student(int id, String firstName, String lastName, String branch, int year, String mobileNumber) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
        this.branch = branch;
        this.year = year;
        this.mobileNumber = mobileNumber;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    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 String getBranch() {
        return branch;
    }

    public void setBranch(String branch) {
        this.branch = branch;
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }

    public String getMobileNumber() {
        return mobileNumber;
    }

    public void setMobileNumber(String mobileNumber) {
        this.mobileNumber = mobileNumber;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", firstName='" + firstName + '\'' +
                ", lastName='" + lastName + '\'' +
                ", branch='" + branch + '\'' +
                ", year=" + year +
                ", mobileNumber='" + mobileNumber + '\'' +
                '}';
    }
}

Whitelabel错误页面此应用程序没有针对/ error的显式映射，因此您将其视为后备。

发生意外错误（类型=内部服务器错误，状态= 500）。在[java.lang.String]类型上找不到属性[id]

Answer 1

我认为，可能是因为您的jsp中的jstl表达式不正确
尝试取代这个 <c:forEach var="student" items="students"> 对此 <c:forEach var="student" items="${students}">

Answer 2

students指向学生对象列表，而不是字符串。因此将其包装在$ {}

之间

items="${students}">

在类型[java.lang.String]上找不到属性[id]

2 个答案: