java - Spring MVC 转换方法

Question

我有车辆服务，其中包括零件 list 。添加新服务不是问题，查看服务也不是问题，但是当我尝试实现编辑时，它不会预先选择零件列表。因此，认为这是 Thymeleaf 问题，我发布了问题 here .

我得到的答案是尝试实现 spring 转换服务。我就是这么做的(我想)，现在我需要帮助来摆脱困境。问题是 View 将服务中的部件实例与包含所有部件的 partsAttribute 形式的部件实例进行比较，并且从不使用转换器，因此它不起作用。我没有收到任何错误...只是在 View 中，未选择零件。下面您将找到转换器、WebMVCConfig、PartRepository、ServiceController 和 html w/thymeleaf，供您引用。我究竟做错了什么？？？

转换器:

部分到字符串:

    public class PartToStringConverter implements  Converter<Part, String> {   
    /** The string that represents null. */
    private static final String NULL_REPRESENTATION = "null";

    @Resource
    private PartRepository partRepository;

    @Override
    public String convert(final Part part) {
        if (part.equals(NULL_REPRESENTATION)) {
                return null;
        }
        try {
          return part.getId().toString();
        }
        catch (NumberFormatException e) {
            throw new RuntimeException("could not convert `" + part + "` to an valid id");
        }
    }
}

字符串到部分:

public class StringToPartConverter implements  Converter<String, Part> {   
        /** The string that represents null. */
        private static final String NULL_REPRESENTATION = "null";

        @Resource
        private PartRepository partRepository;

        @Override
        public Part convert(final String idString) {
            if (idString.equals(NULL_REPRESENTATION)) {
                    return null;
            }
            try {
              Long id = Long.parseLong(idString);
              return this.partRepository.findByID(id);
            }
            catch (NumberFormatException e) {
                throw new RuntimeException("could not convert `" + id + "` to an valid id");
            }
        }
    }

WebMvcConfig 的相关部分:

@Configuration
public class WebMvcConfig extends WebMvcConfigurationSupport {
...
    @Bean(name="conversionService")
    public ConversionService getConversionService(){
        ConversionServiceFactoryBean bean = new ConversionServiceFactoryBean();
        bean.setConverters(getConverters());
        bean.afterPropertiesSet();
        ConversionService object = bean.getObject();
        return object;
    }
    private Set<Converter> getConverters() {
        Set<Converter> converters = new HashSet<Converter>();

        converters.add(new PartToStringConverter());
        converters.add(new StringToPartConverter());
        System.out.println("converters added");
        return converters;
    }
}

零件存储库如下所示:

@Repository
@Transactional(readOnly = true)
public class PartRepository {

protected static Logger logger = Logger.getLogger("repo");

    @PersistenceContext
    private EntityManager entityManager;

    @Transactional
    public Part update(Part part){
        try {
            entityManager.merge(part);
            return part;
        } catch (PersistenceException e) {
            return null;
        }
    }

    @SuppressWarnings("unchecked")
    public List<Part> getAllParts(){
        try {
            return entityManager.createQuery("from Part").getResultList();
        } catch (Exception e) {
            return new ArrayList<Part>();
        }
    }

    public Part findByID(Long id){
        try {
            return entityManager.find(Part.class, id);
        } catch (Exception e) {
            return new Part();
        }
    }
}

编辑ServiceController的部分内容:

    @Controller
    @RequestMapping("/")
    public class ServisController {

        protected static Logger logger = Logger.getLogger("controller");

        @Autowired
        private ServisRepository servisRepository;
        @Autowired
        private ServisTypeRepository servisTypeRepo;
        @Autowired
        private PartRepository partRepo;
        @Autowired
        private VehicleRepository2 vehicleRepository;   

        /*-- **************************************************************** -*/
    /*--  Editing servis methods                                          -*/
    /*--                                                                  -*/
    /*-- **************************************************************** -*/

        @RequestMapping(value="/admin/servisi/editServis", method = RequestMethod.GET)
        public String getEditServis(@RequestParam(value="id", required=true) Long id, Model model){
            logger.debug("Received request to show edit page");

            List<ServisType> servisTypeList = servisTypeRepo.getAllST();
            List<Part> partList = partRepo.getAllParts();
            List<Part> selectedParts = new ArrayList<Part>();
            Servis s = servisRepository.getById(id);
            for (Part part : partList) {
                for (Part parts : s.getParts()) {
                    if(part.getId()==parts.getId()){
                        selectedParts.add(part);
                        System.out.println(part);
                    }
                }
            }
            s.setParts(selectedParts);

            logger.debug("radjeni dijelovi " + s.getParts().toString());
            logger.debug("radjeni dijelovi " + s.getParts().size());
            s.setVehicle(vehicleRepository.findByVin(s.getVehicle().getVin()));
            model.addAttribute("partsAtribute", partList);
            model.addAttribute("servisTypesAtribute", servisTypeList);
            model.addAttribute("servisAttribute", s);

            return "/admin/servis/editServis";
        }

        @RequestMapping(value="/admin/servisi/editServis", method = RequestMethod.POST)
        public String saveEditServis(@ModelAttribute("servisAttribute") @Valid Servis servis, BindingResult result){
            logger.debug("Received request to save edit page");
            if (result.hasErrors()) 
            {
                String ret = "/admin/servis/editServis";
                return ret;
            }

            servisRepository.update(servis);

            return "redirect:/admin/servisi/listServis?id="+servis.getVehicle().getVin();
        }
}

View 正确显示服务，只是它没有预选部分。

编辑服务:

<!DOCTYPE html SYSTEM "http://www.thymeleaf.org/dtd/xhtml1-strict-thymeleaf-spring3-3.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:th="http://www.thymeleaf.org">
<head th:include="fragments/common :: headFragment">
<title>Edit Vehicle Service</title>
</head>
<body>

<div th:include="fragments/common :: adminHeaderFragment"></div>

<div class="container">

<section id="object">
  <div class="page-header">
    <h1>Edit service</h1>
  </div>

<div class="row">

    <form action="#" th:object="${servisAttribute}"
        th:action="@{/admin/servisi/editServis}" method="post" class="form-horizontal well">

        <input type="hidden" th:field="*{vehicle.vin}" class="form-control input-xlarge" />
          <div class="form-group" th:class="${#fields.hasErrors('vehicle.vin')} ? 'form-group has-error' : 'form-group'">
          <label for="vehicle.licensePlate" class="col-lg-2 control-label">License Plate</label>
            <div class="col-lg-10">
                <input type="text" th:field="*{vehicle.licensePlate}" class="form-control input-xlarge" placeholder="License Plate" readonly="readonly"/>
              <p th:if="${#fields.hasErrors('vehicle.licensePlate')}" class="label label-danger" th:errors="*{vehicle.licensePlate}">Incorrect LP</p>
            </div>
          </div>    
          <div class="form-group" th:class="${#fields.hasErrors('serviceDate')} ? 'form-group has-error' : 'form-group'">
          <label for="serviceDate" class="col-lg-2 control-label">Servis Date: </label>
            <div class="col-lg-10">
              <input type="date" th:field="*{serviceDate}" class="form-control input-xlarge" placeholder="Servis Date" />
              <p th:if="${#fields.hasErrors('serviceDate')}" class="label label-danger" th:errors="*{serviceDate}">Incorrect Date</p>
            </div>
          </div>
          <div class="form-group" th:class="${#fields.hasErrors('serviceType.id')} ? 'form-group has-error' : 'form-group'">
          <label for="serviceType.id" class="col-lg-2 control-label">Vrsta Servisa</label>
            <div class="col-lg-10">
                <select th:field="*{serviceType.id}" class="form-control">
                <option th:each="servisType : ${servisTypesAtribute}" 
                        th:value="${servisType.id}" th:selected="${servisType.id==servisAttribute.serviceType.id}"
                        th:text="${servisType.name}">Vrsta Servisa</option>
                </select>
              <p th:if="${#fields.hasErrors('serviceType.id')}" class="label label-danger" th:errors="${serviceType.id}">Incorrect VIN</p>
            </div>
          </div>
          <div class="form-group" th:class="${#fields.hasErrors('parts')} ? 'form-group has-error' : 'form-group'">
          <label for="parts" class="col-lg-2 control-label">Parts</label>
            <div class="col-lg-10">
                <select class="form-control" th:field="*{parts}" multiple="multiple" >
                <option th:each="part : ${partsAtribute}" 
                        th:field="*{parts}"
                        th:value="${part.id}"
                        th:text="${part.Name}">Part name and serial No.</option>
                </select>
              <p th:if="${#fields.hasErrors('parts')}" class="label label-danger" th:errors="*{parts}">Incorrect part ID</p>
            </div>
          </div>
          <div class="form-group" th:class="${#fields.hasErrors('completed')} ? 'form-group has-error' : 'form-group'">
          <label for="completed" class="col-lg-2 control-label">Is service completed?</label>
            <div class="col-lg-10">
              <select th:field="*{completed}" class="form-control">
                <option value="true">Yes</option>
                <option value="false">No</option>
              </select>
              <p th:if="${#fields.hasErrors('completed')}" class="label label-danger" th:errors="*{completed}">Incorrect checkbox</p>
            </div>
          </div>
        <hr/>
          <div class="form-actions">
            <button type="submit" class="btn btn-primary">Edit Service</button>
            <a class="btn btn-default" th:href="@{/admin/servisi/listServis(id=${servisAttribute.vehicle.vin})}">Cancel</a>
          </div>
    </form>

</div>
</section>

<div class="row right">
  <a class="btn btn-primary btn-large" th:href="@{/admin/part/listPart}">Back to list</a>
</div> 

<div th:include="fragments/common :: footerFragment"></div>
</div>
<!-- /.container -->
<div th:include="fragments/common :: jsFragment"></div>

</body>
</html>

更新:在 Avnish 的帮助下，我做了一些更改，这就是我得到的结果:

添加转换服务不起作用，因此在研究和阅读文档后，返回并更改了我的 WebMvcConfig 文件，因此我添加了这个文件而不是@Bean(我所要做的就是查看 WebMvcConfigurationSupport 上的文档:

@Override
    protected void addFormatters(FormatterRegistry registry){
        registry.addFormatter(new PartTwoWayConverter());
    }

然后我删除了转换器，只制作了一个可以发挥魔力的格式化程序。不要被这个名字迷惑了，它是格式化程序:

public class PartTwoWayConverter implements Formatter<Part>{

    /** The string that represents null. */
    private static final String NULL_REPRESENTATION = "null";

    @Resource
    private PartRepository partRepository;

    public PartTwoWayConverter(){
        super();
    }

    public Part parse(final String text, final Locale locale) throws ParseException{
        if (text.equals(NULL_REPRESENTATION)) {
            return null;
        }
        try {
            Long id = Long.parseLong(text);
        // Part part = partRepository.findByID(id); // this does not work with controller
        Part part = new Part(); // this works
        part.setId(id);         // 
        return part;
        }
        catch (NumberFormatException e) {
            throw new RuntimeException("could not convert `" + text + "` to an valid id");
        }       
    }

    public String print(final Part part, final Locale locale){
        if (part.equals(NULL_REPRESENTATION)) {
            return null;
        }
        try {
            return part.getId().toString();
        }
        catch (NumberFormatException e) {
            throw new RuntimeException("could not convert `" + part + "` to an valid id");
        }
    }

}

然后我编辑了 HTML。无法让 thymeleaf 发挥作用，所以我这样做了:

<div class="form-group" th:class="${#fields.hasErrors('parts')} ? 'form-group has-error' : 'form-group'">
      <label for="parts" class="col-lg-2 control-label">Parts</label>
        <div class="col-lg-10">
            <select class="form-control" id="parts" name="parts" multiple="multiple" >
            <option th:each="part : ${partsAtribute}" 
                    th:selected="${servisAttribute.parts.contains(part)}"
                    th:value="${part.id}"
                    th:text="${part.name}">Part name and serial No.</option>
            </select>
          <p th:if="${#fields.hasErrors('parts')}" class="label label-danger" th:errors="*{parts}">Incorrect part ID</p>
        </div>
      </div>

最后，在经历了很多我无法弄清楚的麻烦和转换错误之后，更改了我的 Controller 更新方法:

@RequestMapping(value="/admin/servisi/editServis", method = RequestMethod.POST)
    public String saveEditServis(@ModelAttribute("servisAttribute") @Valid Servis servis, BindingResult result){
        logger.debug("Received request to save edit page");
        if (result.hasErrors()) 
        {
            logger.debug(result);
            String ret = "/admin/servis/editServis";
            return ret;
        }
        List<Part> list = new ArrayList<Part>();
        for (Part part : servis.getParts()) {
            list.add(partRepo.findByID(part.getId()));
        }
        Servis updating = servisRepository.getById(servis.getId());

        updating.setCompleted(servis.getCompleted());
        updating.setParts(list); // If just setting servis.getParts() it does not work
        updating.setServiceDate(servis.getServiceDate());
        updating.setServiceType(servis.getServiceType());

        servisRepository.update(updating);

        return "redirect:/admin/servisi/listServis?id="+servis.getVehicle().getVin();
    }

尽管这有效，但我仍然不高兴，因为这段代码看起来更像是修补而不是正确的编码。仍然困惑为什么从partRepository 返回Part 不起作用。以及为什么 thymeleaf 不起作用......如果有人可以将我带到正确的方向，我将不胜感激!

Answer 1

Thymeleaf 使用 Spring 框架 SelectedValueComparator.isSelected 比较值(用于在选项 html 中包含 selected="selected"标签)，这本质上首先依赖于 java 相等性。如果失败，它将回退到两个值的字符串表示形式。以下是其文档的摘录

<小时/>

用于测试候选值是否与数据绑定(bind)值匹配的实用程序类。热切地尝试通过多种途径来证明比较，以处理实例不平等、逻辑(基于字符串表示)相等和基于 PropertyEditor 的比较等问题。
为比较数组、集合和映射提供全面支持。
平等契约
对于单值对象，首先使用标准 Java 相等性来测试相等性。因此，用户代码应努力实现 Object.equals 以加快比较过程。如果 Object.equals 返回 false，则尝试进行详尽的比较，目的是证明相等性而不是反驳它。
接下来，尝试比较候选值和绑定(bind)值的字符串表示形式。在许多情况下，这可能会导致 true，因为这两个值在显示给用户时都将表示为字符串。
接下来，如果候选值是字符串，则尝试将绑定(bind)值与将相应的 PropertyEditor 应用到候选值的结果进行比较。此比较可以执行两次，一次针对直接 String 实例，然后如果第一次比较结果为 false，则针对 String 表示形式。

<小时/>

对于您的具体情况，我会写下转换服务，以便将我的零件对象转换为字符串，如 http://www.thymeleaf.org/doc/html/Thymeleaf-Spring3.html#configuring-a-conversion-service 中的 VarietyFormatter 中所述。 。发布此内容时，我将使用 th:value="${part}"并让 SelectedValueComparator 完成比较对象的魔力，并在 html 中添加 selected="selected"部分。

此外，在我的设计中，我总是基于主键实现 equals 方法(通常我在所有其他实体继承的顶级抽象实体中执行此操作)。这进一步增强了我的系统中域对象的自然比较。你在设计中也在做类似的事情吗？

希望对你有帮助!!