Question

在我目前的春季项目中，我有一个具有此输入字段的表单：

                    <div class="panel panel-default">
                        <div class="panel-heading">
                            <form:label path="${entry.key}">${entry.key}</form:label>
                        </div>
                        <div class="panel-body">
                            <form:select path="${entry.key}.id" class="form-control">
                                <form:options items="${values[entry.key]}" itemValue="id" itemLabel="nome"/>
                            </form:select>
                        </div>
                    </div>

如果用户不想选择一个选项（数据库中的atribute可以为null），我想添加一个默认值。我试试这个：

1 -

<form:option value="-" label="--Please Select"/>

2 -

<form:option value="" label="--Please Select"/>

3 -

<form:option value="" label="--Please Select" disabled="disabled"/>

但这些选项都不起作用（我收到错误

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.spring.loja.model.categoria.persistence.model.Categoria

当我运行应用程序时）。

任何人都可以告诉我实现这一目标的正确方法是什么？

更新

我项目中的2个实体类。上面的代码适用于第一个（Product），但是当我尝试插入第二个（Order）时，我得到错误TransientObjectException。

实体类：产品

@Entity
@Table(name="produto")
public class Produto {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;

    @Column(name="nome", unique=true)
    @Order(value=1)
    private String nome;

    @Column(name="preco")
    @Order(value=2)
    private Float preco;

    @OneToOne
    @JoinColumn(name="categoria")
    @Order(value=3)
    private Categoria categoria;

    @Column(name="resumo", length=140)
    @Order(value=4)
    private String resumo;

    @Column(name="descricao", length=65535)
    @Order(value=5)
    private String descricao;
}

实体类：订单

@Entity
@Table(name="pedido")
public class Pedido {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;

    @OneToOne(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinColumn(name="cliente")
    @Order(value=1)
    private Cliente cliente;

    @OneToOne(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinColumn(name="produto")
    @Order(value=2)
    private Produto produto;

    @OneToOne(fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
    @JoinColumn(name="cobranca")
    @Order(value=3)
    private Cobranca cobranca;
}

更新2

我试试这个：

                            <form:select path="${entry.key}.id" class="form-control">
                                <form:option value="" label="--Please Select"/>
                                <form:options items="${values[entry.key]}"></form:options>
                            </form:select>

这样，当我尝试插入新值时出现错误。有了这个：

                            <form:select path="${entry.key}" class="form-control">
                                <form:option value="" label="--Please Select"/>
                                <form:options items="${values[entry.key]}"></form:options>
                            </form:select>

我只能在没有选择选项的情况下插入新项目。我试试这个实体类：

@Entity
@Table(name="pagina")
public class Pagina {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "nome", unique=true, nullable=false, length=32)
    @Order(value=1)
    private String nome;

    @Column(name = "titulo", nullable=false, length=32)
    @Order(value=2)
    private String titulo;

    @Column(name="resumo", length=140)
    @Order(value=3)
    private String resumo;

    @Column(name = "descricao", length=65535)
    @Order(value=4)
    private String descricao;

    @OneToOne(fetch = FetchType.EAGER, cascade = {CascadeType.ALL}, optional=true)
    @JoinColumn(name="pagina")
    @Order(value=5)
    private Pagina pagina;

    @OneToOne(fetch = FetchType.EAGER, cascade = {CascadeType.ALL}, optional=true)
    @JoinColumn(name="produto")
    @Order(value=6)
    private Produto produto;
}

任何人都可以看到这里有什么问题？

Answer 1

我不确定TransientObjectException的原因，但下面是如何将默认值设置为form的简单示例：select。希望这会有所帮助。

<强> JSP：

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<html>
<head>
<title>example</title>
</head>
<body>
  <form:form modelAttribute="myForm" method="post">
    <form:select path="valueOfSelectElement">
      <form:option value="default-value" label="--Please Select" />
      <form:options items="${options}" itemValue="id" itemLabel="name" />
    </form:select>
    <input type="submit" />
  </form:form>
</body>
</html>

<强>控制器：

package org.myorg.myapp;

import java.util.Arrays;
import java.util.List;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class MyController {

  @RequestMapping(value = "/form", method = RequestMethod.GET)
  public ModelAndView showForm() {
    ModelAndView mav = new ModelAndView("form");
    List<IdAndName> options = Arrays.asList(
        new IdAndName("id1", "name1"),
        new IdAndName("id2", "name2"),
        new IdAndName("id3", "name3")
    );
    mav.addObject("options", options);

    MyForm myForm = new MyForm();
    myForm.setValueOfSelectElement("default-value");
    mav.addObject("myForm", myForm);

    return mav;
  }

  @RequestMapping(value = "/form", method = RequestMethod.POST)
  @ResponseBody
  public String processForm(MyForm myForm) {
    return myForm.getValueOfSelectElement();
  }

  static class MyForm {
    private String valueOfSelectElement;

    public String getValueOfSelectElement() {
      return valueOfSelectElement;
    }

    public void setValueOfSelectElement(String valueOfSelectElement) {
      this.valueOfSelectElement = valueOfSelectElement;
    }
  }

  static class IdAndName {
    private String id;

    private String name;

    public IdAndName(String id, String name) {
      this.id = id;
      this.name = name;
    }

    public String getId() {
      return id;
    }

    public void setId(String id) {
      this.id = id;
    }

    public String getName() {
      return name;
    }

    public void setName(String name) {
      this.name = name;
    }
  }
}

Answer 2

要为您的选择表单设置默认值，请选择=＆＃34;选择＆＃34;属性到您的表单：选项标记。但我不确定你的org.hibernate.TransientObjectException是否以某种方式与

表单的默认值：select

2 个答案: