Spring-Hibernate-MySQL 应用程序中的 javax.el.PropertyNotFoundException : Property not found on type java. lang.String

Question

我有一个 mysql 查询，如果我在 mysql 工作台的查询编辑器中运行它，它会返回多行。现在我想将查询结果推送到列表，将列表添加到模型，并在 View 中显示结果。但是，我收到错误。我做错了什么，如何解决这个问题？

来自 Controller 的代码片段:

  @Transactional
        @RequestMapping(value = "/question-editor", method = RequestMethod.GET)
        public ModelAndView viewQuestionsToEdit(@RequestParam("username")String user, ModelAndView model, Principal principal){

                model.setViewName("question-editor");

                int id2 = 0;
                try
                {
                        if(user != null)
                                id2 = Integer.parseInt(user);
                }
                catch (NumberFormatException e)
                {
                        id2 = 0;
                }

                Question question = em.find(com.databaseproject.questor.model.Question.class, id2);
                model.addObject("question", question);

                List<Question> questions = (List<Question>)em.createNativeQuery("SELECT q.questionText FROM question q WHERE idQuestion IN (SELECT qchq.Question_idQuestion FROM questioncart_has_question qchq JOIN (SELECT qc.idQuestionCart FROM questioncart qc WHERE User_username =:id2 ORDER BY idQuestionCart DESC LIMIT 1) qc ON qchq.QuestionCart_idQuestionCart = qc.idQuestionCart );")
                                .setParameter("id2", user).getResultList();

                model.addObject("questionstoedit", questions);

                String name = principal.getName(); //get logged in username
                model.addObject("username", name);

                return model;
        }

尝试将值获取到 jsp View 文件中:

<c:forEach var="question" items="${questionstoedit}">
   <p>Question no. ${question.questionText}</p>
</c:forEach>

我收到的错误是:

javax.el.PropertyNotFoundException: Property 'questionText' not found on type java.lang.String

这是模型类:Question.java:

package com.databaseproject.questor.model;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Transient;

@Entity
public class Question {

    @Id
    private int idQuestion;
    private String questionText;
    private String solutionText;
    private byte[] image;
    private String filepath;
    private int year;
    private String User_username;
    private int Teacher_idTeacher;
    private String Course_coursecode;

    @Transient
    private String encodedImage;

    public int getIdQuestion() {
        return idQuestion;
    }

    public void setIdQuestion(int idQuestion) {
        this.idQuestion = idQuestion;
    }

    public String getQuestionText() {
        return questionText;
    }

    public void setQuestionText(String questionText) {
        this.questionText = questionText;
    }

    public String getSolutionText() {
        return solutionText;
    }

    public void setSolutionText(String solutionText) {
        this.solutionText = solutionText;
    }

    public byte[] getImage() {
        return image;
    }

    public void setImage(byte[] image) {
        this.image = image;
    }

    public String getFilepath() {
        return filepath;
    }

    public void setFilepath(String filepath) {
        this.filepath = filepath;
    }

    public int getYear() {
        return year;
    }

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

    public String getUser_username() {
        return User_username;
    }

    public void setUser_username(String user_username) {
        User_username = user_username;
    }

    public int getTeacher_idTeacher() {
        return Teacher_idTeacher;
    }

    public void setTeacher_idTeacher(int teacher_idTeacher) {
        Teacher_idTeacher = teacher_idTeacher;
    }

    public String getCourse_coursecode() {
        return Course_coursecode;
    }

    public void setCourse_coursecode(String course_coursecode) {
        Course_coursecode = course_coursecode;
    }

    public String getEncodedImage() {
        return encodedImage;
    }

    public void setEncodedImage(String encodedImage) {
        this.encodedImage = encodedImage;
    }
}

Answer 1

将返回类型更改为字符串列表:

List<String> questions = (List<String>)em.createNativeQuery("...");

您正在选择字符串的List，如果没有特定的映射器，则无法将其映射到 Question 类。

在 JSP 上应用此更改:

<c:forEach var="question" items="${questionstoedit}">
   <p>Question no. ${question}</p>
</c:forEach>