org.hibernate.TypeMismatchException：取数据时提供了错误类型的id

Question

    @Transactional
            @RequestMapping(value = "/question-list", method = RequestMethod.GET)
            public ModelAndView viewQuestionList(@RequestParam("course-code")String code, ModelAndView model){

                    model.setViewName("question-list");

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

                    List<Question> questions = 

(List<Question>)em.createQuery("SELECT q FROM Question q WHERE q.Course_coursecode =: code")
                        .setParameter("code", code).getResultList();

                model.addObject("questionList", questions);

                return model;
        }

org.springframework.web.util.NestedServletException：请求处理失败；嵌套异常为java.lang.IllegalArgumentException：为类com.DatabaseProject.Questor.Model.Question提供了错误类型的id。应为：class java.lang.Integer，got class java.lang.String

有趣的是，当我输入一个int值作为搜索查询时，得到的结果是：

org.hibernate.TypeMismatchException：为类com.databaseproject.questor.model.question提供了错误类型的id。应为：class java.lang.Integer，got class java.lang.String

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

如@jb Nizet所指出的，观察实体，您正试图通过id查找一个问题

Question question = em.find(com.databaseproject.questor.model.Question.class, code);

传递字符串的“代码”。如果“code”表示id,则应将其转换为int：

model.setViewName("question-list");
int id = 0;
try
{
    if(code != null)
      id = Integer.parseInt(code);
}
catch (NumberFormatException e)
{
    id = 0;
}
Question question = em.find(com.databaseproject.questor.model.Question.class, id);

处理一个可能找不到的问题。如果“code”不是id，您应该进行一个查询（带有标准，本机或jpql）以获得一个问题实体列表，从中得到您需要的一个。

TypedQuery<Question> query = em.createQuery("SELECT q FROM Question q WHERE q.Course_coursecode = :coursecode", Question.class);
query.setParameter("coursecode", code);
List<Question> results = query.getResultList();