关于hibernate复合模式的帮助

Question

所以我被卡住了，我正在创建一个 gwt Web 应用程序，我将使用树（gwt Tree 和 TreeItems）结构来显示文件夹列表（类文件夹）和文件（类 FileLocation）、文件夹和文件位置类都将实现基于复合模式的类的层次结构接口。但我正在使用休眠来存储我的数据，并且我正在使用注释将数据映射到数据库。我的麻烦是我不知道如何注释我的界面。

你们中的任何人在使用 hibernate 持久化数据时使用复合模式

public interface Hierarchy(){
// a few abstract methods that will be implemented by the sub classes
 }


@Entity
@Table()
public class Folder implements Serializable, Hierarchy {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "folder_id", updatable = false, nullable = false)
private int id;
@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
@JoinTable(name = "FOLDER_FILELOCATION", joinColumns = { 
        @JoinColumn(name = "folder_id") }, inverseJoinColumns = { 
        @JoinColumn(name = "file_information_id") })
private List<Hierarchy> children = new ArrayList<Hierarchy>() ;
@Column(name = "folder_name")
private String folderName;
@Column(name = "tree_item")
private TreeItem item;
@Column (name = "parent")
private Hierarchy parent;



@Entity
@Table(name = "FILE_INFORMATION_TABLE")
public class FileInformation implements Serializable, Hierarchy {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "file_information_id", updatable = false, nullable = false)
private int fiId;
@Column (name = "location")
private String location;
@Column(name = "tree_item")
private TreeItem item;
@Column (name = "parent")
    @ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )
    @JoinTable(name="FOLDER_FILELOCATION",
    joinColumns = @JoinColumn(name="filelocation_id"),
    inverseJoinColumns = @JoinColumn(name="folder_ID"))  
private Hierarchy parent;

Answer 1

在查看了休眠文档和This Book 之后，我找到了解决问题的方法。我暂时无法使用带有 JPA 注释的接口。所以我使用了一个带有支持继承的映射的抽象类。在此示例中，我使用单个表来存储所有值。但我会考虑将它们分开。

@Entity
@Table(name ="HIERARCHY")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(
    name = "HIERARCHY_TYPE", discriminatorType = DiscriminatorType.STRING)      
public abstract class  Hierarchy implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "hierarchy_id", updatable = false, nullable = false)
private int hId;



@Entity
@DiscriminatorValue("F")
public class Folder extends Hierarchy  {

@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
@JoinTable(name = "FOLDER_JOIN_FILELOCATION", joinColumns = { 
        @JoinColumn(name = "folder_id") }, inverseJoinColumns = { 
        @JoinColumn(name = "file_information_id") })
private List<Hierarchy> children = new ArrayList<Hierarchy>() ;
@Column(name = "folder_name")
private String folderName;
//@Column(name = "tree_item")
//private TreeItem item;
@ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )
   @JoinTable(name="FOLDER_JOIN_FOLDER",
        joinColumns = @JoinColumn(name="parent_folder_id"),
        inverseJoinColumns = @JoinColumn(name="folder_ID")
    ) 
private Hierarchy parent;




@Entity
@DiscriminatorValue("FI")
public class FileInformation extends Hierarchy  {


@Column (name = "location")
private String location;
//@Column(name = "tree_item")
//private TreeItem item;
@ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )
   @JoinTable(name="FILEINFORMATION_JOIN_FOLDER",
        joinColumns = @JoinColumn(name="filelocation_id"),
        inverseJoinColumns = @JoinColumn(name="folder_ID")
    )  
private Hierarchy parent;

Answer 2

Composite 是非常基本的休眠映射，应该不是问题。
但我不明白映射。我假设 FOLDER_FILELOCATION 是文件夹和文件信息之间的链接表。如果是这样，您实际上没有 OneToMany 而是 ManyToMany 关系。但是您可以将其映射为 OneToMany。
您面临的问题是什么？ 要获得更准确的答案，请花更多时间解释您的具体问题。格式化给定的代码也有帮助，但好​​的，我会试一试。

我不太确定，但我认为根据我假设你拥有的模型，你应该试试这个：

public interface Hierarchy(){
// a few abstract methods that will be implemented by the sub classes
}


@Entity
@Table(name = "FOLDER_TABLE")
public class Folder  implements Hierarchy, Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "folder_id", updatable = false, nullable = false)
    private int id;

    @OneToMany
    @JoinTable(
            name="FOLDER_FILELOCATION",
            joinColumns = @JoinColumn( name="folder_id"),
            inverseJoinColumns = @JoinColumn( name="filelocation_id")
    )   
    private List<Hierarchy> children = new ArrayList<Hierarchy>() ;

    @Column(name = "folder_name")
    private String folderName;

    @Column(name = "tree_item")
    private TreeItem item;

    @Column (name = "parent")
    private Hierarchy parent;
}

@Entity
@Table(name = "FILE_INFORMATION_TABLE")
public class FileInformation implements Hierarchy, Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "file_information_id", updatable = false, nullable = false)
    private int fiId;

    @Column (name = "location")
    private String location;
    @Column(name = "tree_item")
    private TreeItem item;

    @ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )
    @JoinTable(name="FOLDER_FILELOCATION",
        joinColumns = @JoinColumn(name="filelocation_id"),
        inverseJoinColumns = @JoinColumn(name="folder_ID")
    )   
    private Hierarchy parent;
}

希望这会有所帮助。

Answer 3

我不能 100% 确定你想要做什么（你是 extending 一个接口，parent 缺少一个 @ManyToOne 注释）但据我所知，接口不受支持通过注释（它们不是 JPA 规范的一部分）。请参阅HHH-4413 和this discussion。为此，您可能需要使用 XML mappings。