spring-mvc - 在 Spring 中循环 JSTL 表单标签内的列表

Question

我有一个 Expense 类，它有一个 ExpenseType 列表类型的字段expenseType。我想在 View 页面上显示 Expense 和 ExpenseType 类中的所有字段。我使用每个标签来显示 ExpenseType 中的所有字段，因为它是 Expense 类中的列表。但这些字段没有呈现在 View 页面上。

在下面的代码中，不显示每个标签内的标签名称和价格。我尝试使用放置在 foreach 标记旁边的 c:out 标记显示一些值，但它从未显示，这意味着它在 c:forEach 处失败

这是我的jsp代码:

    <form:form method="POST" modelAttribute="expenses" action="saveExpense">
          <div class="box-body">
                <div class="form-group col-xs-6 text-spacing">
                      <label>Expense Date</label>
                     <form:input path="date" id="expenseDate" class="form-control"/>
                     <form:errors path="date" cssClass="error" />
                    </div>
                <div class="form-group col-xs-6 text-spacing">
                  <label>Shop/Dealer Name</label>
                  <form:input path="shopName" type="text" class="form-control" placeholder="dealer name"/>
                  <form:errors path="shopName" cssClass="error" />
                </div>
                <div class="container">
                    <div class="row">
                        <div class="col-md-12">
                            <div data-role="dynamic-fields">
                                <div class="form-inline">
                                 <c:forEach items="${expenses.expensesType}" varStatus="status">
                                     <div class="form-group">
                                        <label class="sr-only" for="field-name">Name</label>
                                        <form:input path="expensesType[${status.index}].name" type="text"/>
                                    </div>
                                    <span>-</span>
                                    <div class="form-group">
                                        <label class="sr-only" for="field-value">Price</label>
                                         <form:input path="expensesType[${status.index}].price" type="text"/>
                                    </div>
                                    <button class="btn btn-danger" data-role="remove">
                                        <span class="glyphicon glyphicon-remove"></span>
                                    </button>
                                    <button class="btn btn-primary" data-role="add">
                                        <span class="glyphicon glyphicon-plus"></span>
                                    </button>
                                 </c:forEach>
                                </div>  
                            </div> 
                        </div> 
                    </div>
                </div>
            </div>
          <div class="box-footer">
            <button type="submit" class="btn btn-primary">Save</button>
             <a class="btn btn-primary" href="<c:url value='expensesList'/>"> Cancel </a>
          </div>
      </form:form>

我的 Controller :

    @RequestMapping(value = "/expensesForm", method = RequestMethod.GET)
    public String getForm(Model model) {
        model.addAttribute("expenses", new Expenses());
        return "expensesForm";
    }

    @RequestMapping(value = "/saveExpense", method = RequestMethod.POST)
    public String saveCattleDetails(@Valid @ModelAttribute("expenses") Expenses expenses, BindingResult bindingResult,
            Model model) {
        if (bindingResult.hasErrors()) {
            return "expensesForm";
        }
        expensesService.add(expenses);
        return "redirect:expensesList";
    }

模型类

public class Expenses implements Serializable {

    private static final long serialVersionUID = 668608674926007321L;

    @Id
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid")
    @Column(name = "EXPENSES_ID", unique = true)
    private String id;

    @NotNull
    @Column(name = "DATE")
    private Date date;

    @Column(name = "SHOP_NAME")
    private String shopName;

    @Column(name = "TOTAL_EXPENSE")
    private String totalExpenses;

    @Column(name = "DESCRIPTION")
    private String description;

    @OneToMany(mappedBy = "expenses", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private List<ExpensesType> expensesType;

和

@Entity
@Table(name = "EXPENSES_TYPE")
public class ExpensesType implements Serializable {

    private static final long serialVersionUID = 3002107481242774411L;

    @Id
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid")
    @Column(name = "EXPENSE_TYPE_ID", unique = true)
    private String id;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "EXPENSES_ID")
    private Expenses expenses;

    @Column(name = "NAME")
    private String name;

    @Column(name = "CATEGORY")
    private CategoryType category;

    @Column(name = "PRICE")
    private String price;

未显示这些字段可能会出现什么错误。

Answer 1

当您在模型中添加属性时，即

  model.addAttribute("expenses", new Expenses());

您还没有设置 bean Expenses 的费用类型字段，您只是使用了 new Expenses()。

尝试将字段expenseType 初始化为new ArrayList()。即

Expenses exp = new Expenses();
exp.setExpensesType(new ArrayList());
model.addAttribute("expenses", exp);