hibernate - Spring 和/或 hibernate : Saving many-to-many relations from one side after form submission

Question

上下文

我在两个实体之间有一个简单的关联 - Category和Email (NtoM)。我正在尝试创建用于浏览和管理它们的网络界面。我有一个简单的电子邮件订阅编辑表单，其中包含代表给定电子邮件所属类别的复选框列表(我注册了 Set<Category> 类型的属性编辑器)。

问题

表单显示效果很好，包括标记当前分配的类别(针对现有电子邮件)。但不会将任何更改保存到 EmailsCategories 表(NtoM 映射表，用 @JoinTable 定义的表 - 既不会添加新检查的类别，也不会删除未检查的类别。

代码

电子邮件实体:

@Entity
@Table(name = "Emails")
public class Email
{
    @Id
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid2")
    @Column(length = User.UUID_LENGTH)
    protected UUID id;

    @NaturalId
    @Column(nullable = false)
    @NotEmpty
    @org.hibernate.validator.constraints.Email
    protected String name;

    @Column(nullable = false)
    @Temporal(TemporalType.TIMESTAMP)
    protected Date createdAt;

    @Column
    protected String realName;

    @Column(nullable = false)
    protected boolean isActive = true;

    @ManyToMany(mappedBy = "emails", fetch = FetchType.EAGER)
    protected Set<Category> categories = new HashSet<Category>();

    public UUID getId()
    {
        return this.id;
    }

    public Email setId(UUID value)
    {
        this.id = value;

        return this;
    }

    public String getName()
    {
        return this.name;
    }

    public Email setName(String value)
    {
        this.name = value;

        return this;
    }

    public Date getCreatedAt()
    {
        return this.createdAt;
    }

    public String getRealName()
    {
        return this.realName;
    }

    public Email setRealName(String value)
    {
        this.realName = value;

        return this;
    }

    public boolean isActive()
    {
        return this.isActive;
    }

    public Email setActive(boolean value)
    {
        this.isActive = value;

        return this;
    }

    public Set<Category> getCategories()
    {
        return this.categories;
    }

    public Email setCategories(Set<Category> value)
    {
        this.categories = value;

        return this;
    }

    @PrePersist
    protected void onCreate()
    {
        this.createdAt = new Date();
    }
}

类别实体:

@Entity
@Table(name = "Categories")
public class Category
{
    @Id
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid2")
    @Column(length = User.UUID_LENGTH)
    protected UUID id;

    @NaturalId(mutable = true)
    @Column(nullable = false)
    @NotEmpty
    protected String name;

    @ManyToMany
    @JoinTable(
        name = "EmailsCategories",
        joinColumns = {
            @JoinColumn(name = "idCategory", nullable = false, updatable = false)
        },
        inverseJoinColumns = {
            @JoinColumn(name = "idEmail", nullable = false, updatable = false)
        }
    )
    protected Set<Email> emails = new HashSet<Email>();

    public UUID getId()
    {
        return this.id;
    }

    public Category setId(UUID value)
    {
        this.id = value;

        return this;
    }

    public String getName()
    {
        return this.name;
    }

    public Category setName(String value)
    {
        this.name = value;

        return this;
    }

    public Set<Email> getEmails()
    {
        return this.emails;
    }

    public Category setEmails(Set<Email> value)
    {
        this.emails = value;

        return this;
    }

    @Override
    public boolean equals(Object object)
    {
        return object != null
            && object.getClass().equals(this.getClass())
            && ((Category) object).getId().equals(this.id);
    }

    @Override
    public int hashCode()
    {
        return this.id.hashCode();
    }
}

Controller :

@Controller
@RequestMapping("/emails/{categoryId}")
public class EmailsController
{
    @Autowired
    protected CategoryService categoryService;

    @Autowired
    protected EmailService emailService;

    @ModelAttribute
    public Email addEmail(@RequestParam(required = false) UUID id)
    {
        Email email = null;

        if (id != null) {
            email = this.emailService.getEmail(id);
        }
        return email == null ? new Email() : email;
    }

    @InitBinder
    public void initBinder(WebDataBinder binder)
    {
        binder.registerCustomEditor(Set.class, "categories", new CategoriesSetEditor(this.categoryService));
    }

    @RequestMapping(value = "/edit/{id}", method = RequestMethod.GET)
    public String editForm(Model model, @PathVariable UUID id)
    {
        model.addAttribute("email", this.emailService.getEmail(id));

        model.addAttribute("categories", this.categoryService.getCategoriesList());

        return "emails/form";
    }

    @RequestMapping(value = "/save", method = RequestMethod.POST)
    public String save(@PathVariable UUID categoryId, @ModelAttribute @Valid Email email, BindingResult result, Model model)
    {
        if (result.hasErrors()) {
            model.addAttribute("categories", this.categoryService.getCategoriesList());
            return "emails/form";
        }

        this.emailService.save(email);

        return String.format("redirect:/emails/%s/", categoryId.toString());
    }
}

表单 View :

<form:form action="${pageContext.request.contextPath}/emails/${category.id}/save" method="post" modelAttribute="email">
    <form:hidden path="id"/>
    <fieldset>
        <label for="emailName"><spring:message code="email.form.label.Name" text="E-mail address"/>:</label>
        <form:input path="name" id="emailName" required="required"/>
        <form:errors path="name" cssClass="error"/>

        <label for="emailRealName"><spring:message code="email.form.label.RealName" text="Recipient display name"/>:</label>
        <form:input path="realName" id="emailRealName"/>
        <form:errors path="realName" cssClass="error"/>

        <label for="emailIsActive"><spring:message code="email.form.label.IsActive" text="Activation status"/>:</label>
        <form:checkbox path="active" id="emailIsActive"/>
        <form:errors path="active" cssClass="error"/>

        <form:checkboxes path="categories" element="div" items="${categories}" itemValue="id" itemLabel="name"/>
        <form:errors path="categories" cssClass="error"/>

        <button type="submit"><spring:message code="_common.form.Submit" text="Save"/></button>
    </fieldset>
</form:form>

编辑 - 添加 DAO 代码

( emailService.save() 只是对 emailDao.save() 的代理调用)

public void save(Email email)
{
    this.getSession().saveOrUpdate(email);
}

编辑 2 - 更多调试/日志

一个简单的测试片段:

public void test()
{
    Category category = new Category();
    category.setName("New category");
    this.categoryDao.save(category);

    Email email = new Email();
    email.setName("test@me")
        .setRealName("Test <at> me")
        .getCategories().add(category);
    this.emailDao.save(email);

}

这些是日志:

12:05:34.173 [http-bio-8080-exec-23] DEBUG org.hibernate.SQL - insert into Emails (createdAt, isActive, name, realName, id) values (?, ?, ?, ?, ?)
12:05:34.177 [http-bio-8080-exec-23] DEBUG org.hibernate.persister.collection.AbstractCollectionPersister - Inserting collection: [pl.chilldev.mailer.web.entity.Category.emails#24d190e3-99db-4792-93ea-78c294297d2d]
12:05:34.177 [http-bio-8080-exec-23] DEBUG org.hibernate.persister.collection.AbstractCollectionPersister - Collection was empty

即使有了这个日志，它似乎也有点奇怪 - 它告诉它正在插入带有一个元素的集合，但随后它告诉它是空的......

Answer 1

我们又来了。

双向关联有两个端:所有者端和反向端。所有者一方是没有ma​​ppedBy 属性的一方。要知道实体之间存在哪种关联，JPA/Hibernate 只关心所有者一方。您的代码仅修改反面，而不修改所有者面。

维护对象图的一致性是你的工作。有时拥有不连贯的对象图是可以接受的，但不修改所有者端不会使更改持久化。

所以你需要添加

category.getEmails().add(email);

或者选择电子邮件作为所有者方而不是类别。