带有Hibernate数据保存错误的Spring MVC [英] Spring MVC with Hibernate Data Saving Error

问题描述

我有两张表：公司和汽车。一家公司可以有许多汽车。
我无法正确持续使用汽车。从下拉菜单中选择公司。

我的控制器

  @RequestMapping（/）
 public String view（ModelMap model）{
 Map< String，String> companyList = new HashMap< String，String>（）; 
清单<公司>公司= companyService.listAllCompanies（）; 
 for（Company company：companies）{
 companyList.put（String.valueOf（company.getId（）），company.getName（））; 
} 
 model.addAttribute（companies，companyList）; 
 
 model.addAttribute（汽车，新汽车（））; 
返回汽车/指数; 
} 
 
 @RequestMapping（manage）
 public String manage（@ModelAttribute Automotive汽车，
 BindingResult结果，ModelMap模型）{
模型。 addAttribute（汽车，汽车）; 
 
地图< String，String> companyList = new HashMap< String，String>（）; 
清单<公司> companies = new ArrayList< Company>（）; 
 for（Company company：companies）{
 companyList.put（String.valueOf（company.getId（）），company.getName（））; 
} 
 model.addAttribute（companies，companyList）; 
 automotiveService.addAutomotive（汽车）; 
返回汽车/指数; 
} 
  

我的视图

 < form：form action =/ Automotive / managemodelAttribute =automotive> 
名称：< form：input path =name/> 
说明：< form：input path =description/> 
类型：< form：input path =type/> 
公司：< form：select path =companyitems =$ {companies}/> 
< input type =submit/> 
< / form：form> 
  

Q1>从逻辑上看，公司ID不会被保存，保存它应该是一个公司类型的对象。我应该如何解决这个问题。我需要使用DTO还是有直接方法？

Q2>我不能直接通过公司列表来查看，而不是在控制器中创建新的地图吗？

解决方案

您可以使用公司的id作为密钥，然后使用转换器，它会自动将数据从表单转换为域对象。就像在这段代码中一样：

  public class CompanyIdToInstanceConverter实现了Converter< String，Company> {
 
 @Inject 
私人CompanyService _companyService; 
 
 @Override 
 public公司转换（final String companyIdStr）{
 return _companyService.find（Long.valueOf（companyIdStr））; 
} 
 
} 
  

在JSP中：

 < form：select path =companyitems =$ {companies}itemLabel =nameitemValue =id/ > 
  

如果您尚未触及此类型，您可能需要详细了解类型转换。它在Spring doc中有完美的描述（我找不到： http://static.springsource.org/spring/docs/3.0.x/reference/validation.html 第5.5段）。

我希望它会帮助你。

I have two tables: Company and Automotive. A company can have many automotives. I am unable to persist an Automotive properly. Company is selected in View page from a drop down.

My Controller

@RequestMapping("/")
public String view(ModelMap model) {
    Map<String, String> companyList = new HashMap<String, String>();
    List<Company> companies = companyService.listAllCompanies();
    for (Company company : companies) {
        companyList.put(String.valueOf(company.getId()), company.getName());
    }
    model.addAttribute("companies", companyList);

    model.addAttribute("automotive", new Automotive());
    return "automotive/index";
}

@RequestMapping("manage")
public String manage(@ModelAttribute Automotive automotive,
        BindingResult result, ModelMap model) {
    model.addAttribute("automotive", automotive);

    Map<String, String> companyList = new HashMap<String, String>();
    List<Company> companies = new ArrayList<Company>();
    for (Company company : companies) {
        companyList.put(String.valueOf(company.getId()), company.getName());
    }
    model.addAttribute("companies", companyList);
    automotiveService.addAutomotive(automotive);
    return "automotive/index";
}

My View

<form:form action="/Automotive/manage" modelAttribute="automotive">
    Name : <form:input path="name" />
    Description : <form:input path="description" />
    Type : <form:input path="type" />
    Company : <form:select path="company" items="${companies}" />
    <input type="submit" />
</form:form>

Q1> Logically as expected Company id would not be saved since here in view its an id but actually while saving it should be an object of type company. How should I solve this. Do I need to use a DTO or is there any direct method?

Q2> Can't i pass Company list directly to view instead of creating a new Map in controller?

解决方案

You can use id of company as a key and then use converter which will automatically convert data from form into domain object. Just like in this code:

public class CompanyIdToInstanceConverter implements Converter<String, Company> {

    @Inject
    private CompanyService _companyService;

    @Override
    public Company convert(final String companyIdStr) {
        return _companyService.find(Long.valueOf(companyIdStr));
    }

}

And in JSP:

<form:select path="company" items="${companies}" itemLabel="name" itemValue="id"/>

You may need to read more about type conversion if you haven't touched this yet. It is perfectly described in Spring doc (I you couldn't find: http://static.springsource.org/spring/docs/3.0.x/reference/validation.html paragraph 5.5).

I hope it would help you.

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