我无法将对象持久保存到我的数据库中。我有一个与 Profil 具有多对一关系的用户。
我的 JSP 只是添加了一个新用户。因此，JSP 包含字段和一个带有所需配置文件的组合框。问题是，当我运行程序时，即使我在comboxBox 中选择了一个配置文件，控制器中的属性user.profil 也是NULL。
这是用户对象：
package com.app.model;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name="user")
public class User {
private long id;
private String firstname;
private String lastname;
private String login;
private String password;
private Profil profil;
public User() {
}
/**
* @param firstname
* @param lastname
* @param login
* @param password
* @param profil
*/
public User(String firstname, String lastname, String login,
String password, Profil profil) {
this.firstname = firstname;
this.lastname = lastname;
this.login = login;
this.password = password;
this.profil = profil;
}
/**
* Get User Id
*
* @return long - User Id
*/
@Id
@Column(name="id", unique = true, nullable = false)
public long getId() {
return id;
}
/**
* Set User Id
*
* @param long - User Id
*/
public void setId(long id) {
this.id = id;
}
/**
* Get User Firstname
*
* @return String - User Firstname
*/
@Column(name="firstname", unique = false, nullable = false)
public String getFirstname() {
return firstname;
}
/**
* Set User Firstname
*
* @param String - User Firstname
*/
public void setFirstname(String firstname) {
this.firstname = firstname;
}
/**
* Get User Lastname
*
* @return String - User Lastname
*/
@Column(name="lastname", unique = false, nullable = false)
public String getLastname() {
return lastname;
}
/**
* Set User Lastname
*
* @param String - User Lastname
*/
public void setLastname(String lastname) {
this.lastname = lastname;
}
/**
* @return the login
*/
@Column(name="login", unique = true, nullable = false)
public String getLogin() {
return login;
}
/**
* @param login the login to set
*/
public void setLogin(String login) {
this.login = login;
}
/**
* @return the password
*/
@Column(name="password", unique = false, nullable = false)
public String getPassword() {
return password;
}
/**
* @param password the password to set
*/
public void setPassword(String password) {
this.password = password;
}
/**
* @return the profil
*/
@ManyToOne( cascade = CascadeType.REFRESH, fetch = FetchType.EAGER )
@JoinColumn( name = "fk_profil_id", nullable = false )
public Profil getProfil() {
return profil;
}
/**
* @param profil the profil to set
*/
public void setProfil(Profil profil) {
this.profil = profil;
}
/* (non-Javadoc)
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return "User [id=" + id + ", firstname=" + firstname + ", lastname="
+ lastname + ", login=" + login + ", password=" + password
+ "]";
}
}
这是 Profile 对象：
package com.app.model;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="profil")
public class Profil {
private long id;
private String name;
public Profil() {
}
/**
* @param id
* @param name
*/
public Profil(long id, String name) {
this.id = id;
this.name = name;
}
/**
* @return the id
*/
@Id
@Column(name="id", unique = true, nullable = false)
public long getId() {
return id;
}
/**
* @param id the id to set
*/
public void setId(long id) {
this.id = id;
}
/**
* @return the name
*/
@Column(name="name", unique = true, nullable = false)
public String getName() {
return name;
}
/**
* @param name the name to set
*/
public void setName(String name) {
this.name = name;
}
/* (non-Javadoc)
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return "Profil [id=" + id + "]";
}
}
这是控制器：
package com.app.web;
import java.util.HashMap;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
import com.app.model.User;
import com.app.service.impl.ProfilService;
import com.app.service.impl.UserService;
@Controller
@RequestMapping("/users")
public class UserController {
@Autowired
private UserService userService;
@Autowired
private ProfilService profilService;
@ModelAttribute("userForm")
public User createForm()
{
return new User();
}
@RequestMapping(value = "/save", method = RequestMethod.POST)
public ModelAndView saveUser ( @ModelAttribute("userForm") User user, BindingResult result ) {
userService.addUser( user );
return new ModelAndView ( "redirect:/users.html" );
}
@RequestMapping(method = RequestMethod.GET)
public ModelAndView viewUsers() {
Map model = new HashMap();
model.put ( "users", userService.getUsers() );
return new ModelAndView ( "usersView", model );
}
@RequestMapping(value = "/add", method = RequestMethod.GET)
public ModelAndView addUser() {
Map model = new HashMap();
model.put ( "profils", profilService.getProfils() );
return new ModelAndView ( "userAdd", model );
}
}
这是 JSP 页面：
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Add User</title>
</head>
<body>
<h1>Add User</h1>
<c:url var="viewUsersUrl" value="/users.html" />
<a href="${viewUsersUrl}">View Existing Users</a>
<br /><br />
<c:url var="saveUserUrl" value="/users/save.html" />
<form:form modelAttribute="userForm" method="POST" action="${saveUserUrl}">
<form:label path="firstname">Firstname:</form:label>
<form:input path="firstname"/><br />
<form:label path="lastname">Lastname:</form:label>
<form:input path="lastname"/><br />
<form:label path="login">Login:</form:label>
<form:input path="login"/><br />
<form:label path="password">Password:</form:label>
<form:input path="password"/><br />
<form:select path="profil">
<form:option value="0" label="---- Select ----" />
<form:options items="${profils}" itemValue="id" itemLabel="name" />
</form:select>
<input type="submit" value="Save User" />
</form:form>
</body>
</html>
例外：
SEVERE: Servlet.service() for servlet [spring] in context with path [/app] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: Column 'fk_profil_id' cannot be null; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: Column 'fk_profil_id' cannot be null] with root cause
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'fk_profil_id' cannot be null
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
...
...
...
发生此异常是因为 user.profil 在控制器中为 NULL。
如果您需要更多信息，请随时询问。顺便说一句，如果您发现有问题或有更好的方法，请告诉我，我是 spring 和 spring-mvc 的新手。
非常感谢