编辑时id为null的java Spring boot+Thymeleaf对象

Question

从数据表中选择要编辑的费用对象时，控制器中的编辑方法将费用对象发送到编辑屏幕，该屏幕与插入新记录相同。当对象被发送到save方法时，它具有nullo code属性，在该属性中插入而不是更新。我不明白为什么

控制器

@Controller
@RequestMapping("/despesas")
public class DespesaController {

    @Autowired private DespesaService despesaService;
    @Autowired private DespesaRepository despesaRepository;

    @GetMapping("/add")
    public ModelAndView novo(Despesa despesa) {
        ModelAndView model = new ModelAndView("page/cadastro/despesa/cadDespesa");
        model.addObject("tiposDespesa", TipoDespesa.values());
        model.addObject("formasPagamento", FormaPagamento.values());
        model.addObject(despesa);
        return model;
    }

    @PostMapping("/save")
    public ModelAndView salvar(Despesa despesa, BindingResult result, RedirectAttributes attributes) {
        if (result.hasErrors()) {
            return novo(despesa);
        }
        despesa.setDataDespesa(new Date());
        despesaService.salvarDespesa(despesa);
        attributes.addFlashAttribute("mensagem", "Despesa Salva com Sucesso!");
        return new ModelAndView("redirect:/cadastroDespesa");
    }

    @GetMapping("/listDespesa")
    public ModelAndView listagemDeDespesas() {
        ModelAndView model = new ModelAndView("page/cadastro/despesa/listDespesa");
        model.addObject("despesas", despesaRepository.findAll());
        return model;
    }

    @GetMapping("/edit{id}")
    public ModelAndView editar(@PathVariable("id") Long codigo) {
        return novo(despesaRepository.findOne(codigo));
    }
}

FormEdit

<form th:object="${despesa}" method="POST" th:action="@{/despesas/save}">
 <div class="box-body">
    <div class="row">
        <div class="col-md-6">
            <div class="form-group">
                <label>Data</label>
                <div class="input-group">
                    <div class="input-group-addon">
                        <i class="fa fa-calendar"></i>
                    </div>
                    <input type="text" th:field="*{dataDespesa}" class="form-control" disabled="disabled">
                </div>
            </div>
            <div class="form-group">
                <label>Valor</label>
                <div class="input-group">
                    <span class="input-group-addon"><i class="fa fa-dollar"></i></span>
                    <input type="text" th:field="*{valor}" class="form-control">
                </div>
            </div>
        </div>
        <div class="col-md-6">
            <div class="form-group">
                <label>Tipo Despesa</label> 
                    <select class="form-control select2" th:field="*{tipoDespesa}" style="width: 100%;">
                    <option th:each="tipo : ${tiposDespesa}" th:value="${tipo}" th:text="${tipo}"></option>
                </select>
            </div>
            <div class="form-group">
                <label>Forma Pagamento</label> 
                    <select class="form-control select2" th:field="*{formaPagamento}" style="width: 100%;">
                    <option th:each="forma : ${formasPagamento}" th:value="${forma}" th:text="${forma}"></option>
                </select>
            </div>
        </div>

        <div class="col-md-12">
            <div class="form-group">
                <label>Observação</label> 
                <input type="text" th:field="*{observacao}" class="form-control">
            </div>
        </div>
    </div>
 </div>
 <div class="box-footer">
    <button type="submit" class="btn btn-primary">Salvar</button>
    <a class="btn btn-default" th:href="@{/}">Cancelar</a>
 </div>
</form>

选择要编辑的对象的数据表

<table id="example2" class="table table-bordered table-hover">
    <thead>
      <tr>
        <th>Data</th>
        <th>Valor</th>
        <th>Tipo Despesa</th>
        <th>Forma Pagamento</th>
      </tr>
    </thead>
    <tbody>
      <tr th:each="obj : ${despesas}">
        <td data-title="Data" th:text="${#calendars.format(obj.dataDespesa, 'dd/MM/yyyy HH:mm:ss')}"></td>
        <td data-title="Valor" th:text="${#numbers.formatCurrency(obj.valor)}"></td>
        <td data-title="Tipo Despesa" th:text="${obj.tipoDespesa}"></td>
        <td data-title="Forma Pagamento" th:text="${obj.formaPagamento}"></td>
        <td><a th:href="@{/despesas/edit{id} (id=${obj.codigoDespesa})}"><i class="glyphicon glyphicon-pencil"></i></a></td>
      </tr>
    </tbody>
</table>

Answer 1

正如sr.Praneth所说，您需要将要填充的字段添加到表单中，通常ID不可见，但您需要发送它们

<form th:object="${despesa}" method="POST" th:action="@{/despesas/save}">
 <div class="box-body">
 <input type="hidden" th:field="*{id}"/>
 ...  
 </form>

然后，在控制器中，您将能够检索id值，如果是创建，则为null，如果是更新，则为通知