Spring MVC + Hibernate：加载时需要加载id [英] Spring MVC + Hibernate: id to load is required for loading

问题描述

这是一个小问题，我知道，我很抱歉。我试图用Hibernates session.merge（）方法编辑现有记录，我得到以下错误：

  java.lang .IllegalArgumentException：要加载的id是加载
  

所必需的，这是我的对象：

  @Id 
 @GeneratedValue（策略= IDENTITY）
 @Column（名称= title_id的，唯一=真，可为空=假）
 private Integer titleId; 
 
 @NotNull 
 @NotBlank 
 @Column（name =TITLE_DESCRIPTION，nullable = false，length = 10）
 private String titleDescription; 
 //默认构造函数，getters& setters 
  

这是服务层方法：

  public void edit（Title title）{
 logger.debug（Editing existing title）; 
 
 //从Hibernate检索会话
 Session session = sessionFactory.getCurrentSession（）; 
 
 //通过id 
检索现有标题Title existingTitle =（Title）session.get（Title.class，title.getTitleId（））; 
 
 //为此标题分配更新值
 existingTitle.setTitleDescription（title.getTitleDescription（））; 
 
 //保存更新
 session.merge（existingTitle）; 
} 
  

这是控制器的POST方法：

  @RequestMapping（值= /编辑，方法= RequestMethod.POST）
公共字符串postEditTitle（@Valid @ModelAttribute（ titleAttribute）标题标题， 
 BindingResult结果）{
 
 logger.debug（接收到编辑标题的请求）; 
 
 if（result.hasErrors（））{
 returneditTitle; 
} 
 else {
 titleService.edit（title）; 
返回redirect：/ essays / main / title; 
} 
} 
  

我错过了什么？任何帮助将不胜感激。

解决方案

问题不在于Hibernate。 title.getTitleId（）在您传递给 session.get（）时为null，这是您的问题web服务/应用程序。

1. 您的GET可能不会在模型对象中提供id
   
2. 您的客户端代码（表单，客户端应用程序，ajax调用，不管它是什么）可能不会保留GET和POST之间的ID


3. 您的POST可能未提供模型对象中的id 。

您可以在此处提供更多详细信息，或者提出一个新问题，如果您在跨网络保留属性时遇到困难，或WS会话。

This is such a noob question, I know and I apologize. I'm trying to edit existing record with Hibernates session.merge() method and I get the following error:

java.lang.IllegalArgumentException: id to load is required for loading

This is my object:

@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "TITLE_ID", unique = true, nullable = false)
private Integer titleId;

@NotNull
@NotBlank
@Column(name = "TITLE_DESCRIPTION", nullable = false, length = 10)
private String titleDescription;
// default constructor, getters & setters

This is service layer method:

 public void edit(Title title) {
     logger.debug("Editing existing title");

     // Retrieve session from Hibernate
     Session session = sessionFactory.getCurrentSession();

     // Retrieve existing title via id
     Title existingTitle = (Title) session.get(Title.class, title.getTitleId());

     // Assign updated values to this title
     existingTitle.setTitleDescription(title.getTitleDescription());

     // Save updates
     session.merge(existingTitle);
 }

This is controller POST method:

@RequestMapping(value="/edit", method = RequestMethod.POST)
public String postEditTitle(@Valid @ModelAttribute("titleAttribute") Title title,
                        BindingResult result) {

    logger.debug("Received request to edit title");

    if (result.hasErrors()) {
        return "editTitle";
    }
    else {
        titleService.edit(title);
        return "redirect:/essays/main/title";
    }
}

What am I missing? Any help will be much appreciated.

解决方案

The problem isn't with Hibernate. title.getTitleId() is null when you pass it to session.get(), and that's a problem with your web service/application.

1. Your GET might not be providing the id in the model object
2. Your client code (form, client app, ajax call, whatever it is) might not be retaining the ID between the GET and POST
3. Your POST might not be providing the id in the model object.

You can provide more details here, or ask a new question, if you're having difficulties retaining attributes across the web, rest or WS session.

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