為什么“OneToOne”關系允許在資料庫中存盤多個資料

我正在研究OneToOne與 Spring MVC 的關系。在我的代碼Person中是父表和Address子表。我在Person表中保留資料之后Address。我將list of person下拉串列放在地址頁面中，人員下拉串列作為參考，同時將資料保留在子表（地址）中。將資料持久化到兩個表中時我沒有問題，但問題是子表在表中插入多個具有相同外鍵的資料，Address但是，我宣告了OneToOne關系映射，所以，為什么 Hibernate 在表中存盤多個資料時不會產生錯誤Address。

下面是我的代碼：

物體

public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long p_id;

    private String name;
    private String surname;

    @OneToOne(cascade = CascadeType.ALL, mappedBy = "person")
    private Address address;

    // getter setter
}
public class Address {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long a_id;

    private String district;
    private String city;

    @OneToOne(cascade = CascadeType.ALL, targetEntity = Person.class)
    @JoinColumn(name = "p_id")
    private Person person;

    // getter setter
}

控制器

// add person in database
@RequestMapping(value = "/addperson", method = RequestMethod.POST)
public String addPerson(Model mdl, @ModelAttribute("persons") Person person)
{
    pojoService.addPerson(person);
    return "redirect:/persons";
}

// add address in database
@RequestMapping(value = "/addaddress", method = RequestMethod.POST)
public String addAddress(Model mdl, @ModelAttribute("address") Address address)
{
    pojoService.addAddress(address);
    return "redirect:/address";
}

addperson（百里香葉）

<form th:action="@{/addperson}" th:object="${person}" method="post">
        <div class="container">
          <h1 style="text-align: center">Add Person</h1>
          <div class="row">
            <div class="col-sm-12">
                <div class="mb-3">
                  <label for="exampleFormControlInput1" class="form-label">Person name</label>
                  <input type="text" class="form-control" name="name" th:field="*{name}">
                </div>
                <div class="mb-3">
                  <label for="exampleFormControlInput1" class="form-label">Person surname</label>
                  <input type="text" class="form-control" name="surname" th:field="*{surname}">
                </div>
                
                <input class="btn btn-primary" type="submit" value="Submit">
                
                <br>
                <a th:href="@{/}">Home</a>
            </div>
          </div>
        </div>
    </form>

添加地址（百里香葉）

<form th:action="@{/addaddress}" th:object="${address}" method="post">
        <div class="container">
          <h1 style="text-align: center">Add Address</h1>
          <div class="row">
            <div class="col-sm-12">
                <div class="mb-3">
                  <label for="exampleFormControlInput1" class="form-label">Student Name</label>
                  <select th:field="*{person}" class="form-select" aria-label=".Default select example">
                    <th:block th:each="personList: ${person}">
                        <option th:text="${personList.name   ' '   personList.surname}" th:value="${personList.p_id}"></option>
                    </th:block>
                  </select>
                </div>
                <div class="mb-3">
                  <label for="exampleFormControlInput1" class="form-label">District</label>
                  <input type="text" class="form-control" th:field="*{district}">
                </div>
                <div class="mb-3">
                  <label for="exampleFormControlInput1" class="form-label">City</label>
                  <input type="text" class="form-control" th:field="*{city}">
                </div>
                
                <input class="btn btn-primary" type="submit" value="Submit">
                
                <br>
                <a th:href="@{/}">Home</a>
            </div>
          </div>
        </div>
    </form>

結果

人員表：

地址表：

下面我將向您展示我add person和add address頁面的外觀：

uj5u.com熱心網友回復：

在 Spring Framwork 中，我們總是必須參考在子表中存盤外鍵。在您的情況下，您在子表中存盤資料時不能進行任何參考。您必須參考父表主鍵，然后在子表中插入資料。它可以檢查記錄中是否已經存在資料，然后在記錄中更新資料，否則在記錄中插入新資料。

插入子表之前如何參考？

// add person in database
@RequestMapping(value = "/addperson", method = RequestMethod.POST)
public String addPerson(Model mdl, @ModelAttribute("persons") Person person)
{
    pojoService.addPerson(person);
    return "redirect:/persons";
}

// add address in database
@RequestMapping(value = "/addaddress", method = RequestMethod.POST)
public String addAddress(Model mdl, @ModelAttribute("address") Address address)
{
    Person person = address.getPerson();
    person.setAddress(address); 
    pojoService.addAddress(address);
    return "redirect:/address";
}

uj5u.com熱心網友回復：

在你的Person類里面oneToOne映射放orphanRemoval="true" 希望這會解決你的問題

標籤：爪哇 弹簧靴 休眠 弹簧MVC 百里香叶

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