无法将java.lang.String类型的属性值转换为所需类型实体

Question

我是Spring MVC的新手，试图构建一个示例应用程序，我试图将数据保存到一个名为EmployeeDetails的表中，该表与表用户有一对一的关系。提交表单后，我在字段“user”的对象“employee details”中得到了这个错误字段：rejected value[Users]；代码[typemismatch.employeeDetails.user,typemismatch.user,typemismatch.com.sachinmukherjee.spring_hibernate.entity.users,typemismatch]；参数[org.springframework.context.support.defaultmessageSourceResolvable：代码[employeeDetails.user,user]；参数[]；default message[user]]；默认消息[无法将类型“java.lang.String”的属性值转换为属性“user”的必需类型“com.sachinmukherjee.spring_hibernate.entity.users”；嵌套异常为java.lang.IllegalStateException：无法将类型“java.lang.String”的值转换为属性“user”的必需类型“com.sachinmukherjee.spring_hibernate.entity.users”：找不到匹配的编辑器或转换策略]]

用户表结构

+--------------+--------------+------+-----+-------------------+----------------+
| Field        | Type         | Null | Key | Default           | Extra          |
+--------------+--------------+------+-----+-------------------+----------------+
| id           | int(11)      | NO   | PRI | NULL              | auto_increment |
| username     | varchar(20)  | NO   | UNI | NULL              |                |
| password     | varchar(100) | NO   |     | NULL              |                |
| created_at   | datetime     | YES  |     | CURRENT_TIMESTAMP |                |
| userfullname | varchar(50)  | NO   |     | NULL              |                |
+--------------+--------------+------+-----+-------------------+----------------+

Users实体（Users.java）

@Entity
@Table(name="users")
public class Users {

    @Id
    @Column(name="id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    @Column(name="username",unique = true)
    private String username;

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

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

    @Column(name = "created_at")
    private Timestamp created_at;

    @OneToOne(mappedBy = "user",
            cascade = CascadeType.PERSIST
            )
    private EmployeeDetails employee;

    public Users() {
    }

    public Users(String username, String password, String userfullname) {
        this.username = username;
        this.password = password;
        this.userfullname = userfullname;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Timestamp getCreated_at() {
        return created_at;
    }

    public String getUserfullname() {
        return userfullname;
    }

    public void setUserfullname(String userfullname) {
        this.userfullname = userfullname;
    }

    public void setCreated_at(Timestamp created_at) {
        this.created_at = created_at;
    }

    public int getId() {
        return id;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

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

    public EmployeeDetails getEmployee() {
        return employee;
    }

    public void setEmployee(EmployeeDetails employee) {
        this.employee = employee;
    }

    @Override
    public String toString() {
        return "Users [id=" + id + ", username=" + username + ", userfullname=" + userfullname + ", created_at="
                + created_at + "]";
    }
}

EmployeeDetails表结构

+-------------+-------------+------+-----+-------------------+----------------+
| Field       | Type        | Null | Key | Default           | Extra          |
+-------------+-------------+------+-----+-------------------+----------------+
| id          | int(11)     | NO   | PRI | NULL              | auto_increment |
| first_name  | varchar(20) | NO   |     | NULL              |                |
| middle_name | varchar(20) | YES  |     | NULL              |                |
| last_name   | varchar(20) | YES  |     | NULL              |                |
| mobile_no   | bigint(20)  | YES  |     | NULL              |                |
| email       | varchar(50) | NO   |     | NULL              |                |
| created_at  | datetime    | YES  |     | CURRENT_TIMESTAMP |                |
| users_id    | int(11)     | NO   | MUL | NULL              |                |
+-------------+-------------+------+-----+-------------------+----------------+

@Entity
@Table(name="employee_details")
public class EmployeeDetails {

    @Id
    @Column(name="id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

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

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

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

    @Column(name="mobile_no")
    private long mobile_no;

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

    @OneToOne(fetch = FetchType.EAGER,cascade = CascadeType.PERSIST)
    @JoinColumn(name = "users_id")
    private Users user;

    public EmployeeDetails() {

    }

    public EmployeeDetails(String first_name, String middle_name, String last_name, long mobile_no, String email) {
        this.first_name = first_name;
        this.middle_name = middle_name;
        this.last_name = last_name;
        this.mobile_no = mobile_no;
        this.email = email;
    }

    public int getId() {
        return id;
    }

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

    public String getFirst_name() {
        return first_name;
    }

    public void setFirst_name(String first_name) {
        this.first_name = first_name;
    }

    public String getMiddle_name() {
        return middle_name;
    }

    public void setMiddle_name(String middle_name) {
        this.middle_name = middle_name;
    }

    public String getLast_name() {
        return last_name;
    }

    public void setLast_name(String last_name) {
        this.last_name = last_name;
    }

    public long getMobile_no() {
        return mobile_no;
    }

    public void setMobile_no(long mobile_no) {
        this.mobile_no = mobile_no;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Users getUser() {
        return user;
    }

    public void setUser(Users user) {
        this.user = user;
    }

    @Override
    public String toString() {
        return "EmployeeDetails [id=" + id + ", first_name=" + first_name + ", middle_name=" + middle_name
                + ", last_name=" + last_name + ", mobile_no=" + mobile_no + ", email=" + email + ", user=" + user + "]";
    }
}

@Controller
@RequestMapping("/employee_details")
public class EmployeeDetailsController {

    @Autowired
    EmployeeDetailsDAO employeeDetailsDAO;
    @Autowired
    UsersDAO usersDAO;

    @RequestMapping("/")
    public String home(Model model) {
        List<EmployeeDetails> employees = employeeDetailsDAO.getEmployees();
        model.addAttribute("employees", employees);
        return "employee_details/index";
    }

    @GetMapping("/add")
    public String add(Model model) {
        List<Users> users = usersDAO.getUsers();
        EmployeeDetails employee = new EmployeeDetails();
        model.addAttribute("userList",users);
        model.addAttribute("employee", employee);
        return "employee_details/add";
    }

    @PostMapping("/submit")
    public String submit(@ModelAttribute EmployeeDetails employee) {
        System.out.println(employee);
        employeeDetailsDAO.saveEmployee(employee);
        return "redirect:/employee_details/";
    }

}

@Repository
public class EmployeeDetailsDAOImp implements EmployeeDetailsDAO {

    @Autowired
    SessionFactory sessionFactory;

    @Transactional
    public List<EmployeeDetails> getEmployees() {
        Session session = sessionFactory.getCurrentSession();
        Query<EmployeeDetails> query = session.createQuery("from EmployeeDetails",EmployeeDetails.class);
        List<EmployeeDetails> employees = query.getResultList();
        System.out.println(employees);
        return employees;
    }
    @Transactional
    public void saveEmployee(EmployeeDetails employee) {
        Session session = sessionFactory.getCurrentSession();
        session.saveOrUpdate(employee);

    }
}

<form action="${pageContext.request.contextPath}/employee_details/submit" method="POST" modelAttribute="employee" class="form-control">
        <label>Username</label>
        <select name="user" required="required">
             <option>Select User</option>
            <c:forEach var="user" items="${userList}">
                <option value=${user}>${user.username}</option>
            </c:forEach>
        </select>
        <br><br>
        <label>First Name</label>
        <input type="text" name="first_name" />
        <br><br>
        <label>Middle Name</label>
        <input type="text" name="middle_name" />
        <br><br>
        <label>Last Name</label>
        <input type="text" name="last_name" />
        <br><br>
        <label>Email</label>
        <input type="text" name="email" />
        <br><br>
        <button type="submit" class="btn btn-success">Save</button>
    </form>

@Repository
public class UsersDAOImp implements UsersDAO {

    //need to inject session factory
    @Autowired
    private SessionFactory sessionFactory;

    @Transactional
    public List<Users> getUsers() {

        //get the hibernate session
        Session session =  sessionFactory.getCurrentSession();
        //create a query 
        Query<Users> theQuery = 
                     session.createQuery("from Users", Users.class);
        //execute the query and get resultset
        List<Users> users = theQuery.getResultList();
        //return the result
        return users;
    }
}

我不明白为什么会出现这个错误，以及应该在submit方法的method参数中传递什么。

Answer 1

我发现的解决方案是将HTML表单替换为spring表单，并将select标记及其路径更改为如下所示。

<form:label path="user.id">Username</form:label>
        <form:select path="user.id" required="required">
            <form:option value="${user.get(0)}">Select One</form:option>
            <c:forEach var="user" items="${userList}">
                <form:option value="${user.id}">${user.username}</form:option>
            </c:forEach>
</form:select>