Question

我有一个mysql查询，如果我在mysql workbench的查询编辑器中运行它，则返回多行。现在，我想将查询中的结果推送到列表，将列表添加到模型中，并在视图中显示结果。但是，我收到了一个错误。我做错了什么，以及如何解决这个问题？

来自控制器的代码段：

  @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;
        }

尝试将值放入jsp视图文件中：

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

我得到的错误是：

javax.el.PropertyNotFoundException：Property＆＃39; questionText＆＃39;未找到在类型java.lang.String
上

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List个字符串，没有特定的Mapper，它无法映射到Question类。

在JSP上应用此更改：

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

javax.el.PropertyNotFoundException：在Spring-Hibernate-MySQL应用程序中的类型java.lang.String上找不到属性

1 个答案: