0

PostとPost_Imageのテーブルがあります

 @Entity
@Table(name = "post")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Post.findAll", query = "SELECT p FROM Post p"),
    @NamedQuery(name = "Post.findByPostId", query = "SELECT p FROM Post p WHERE p.postId = :postId"),
    @NamedQuery(name = "Post.findByTitle", query = "SELECT p FROM Post p WHERE p.title = :title"),
    @NamedQuery(name = "Post.findByCreatedDatetime", query = "SELECT p FROM Post p WHERE p.createdDatetime = :createdDatetime")})
public class Post implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @NotNull
    @Column(name = "post_id")
    private Integer postId;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 500)
    @Column(name = "title")
    private String title;
    @Basic(optional = false)
    @NotNull
    @Lob
    @Size(min = 1, max = 65535)
    @Column(name = "content")
    private String content;
    @Column(name = "created_datetime")
    @Temporal(TemporalType.TIMESTAMP)
    private Date createdDatetime;
    @JoinColumn(name = "user_id", referencedColumnName = "user_id")
    @ManyToOne(optional = false)
    private User userId;
    @JoinColumn(name = "post_type_id", referencedColumnName = "post_type_id")
    @ManyToOne(optional = false)
    private PostType postTypeId;

    public Post() {
        Date date = new Date();
        this.createdDatetime =new Date(date.getTime());

    }

    public Post(Integer postId) {
        this.postId = postId;
    }

    public Post(Integer postId, String title, String content) {
        this.postId = postId;
        this.title = title;
        this.content = content;
    }

    public Integer getPostId() {
        return postId;
    }

    public void setPostId(Integer postId) {
        this.postId = postId;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public Date getCreatedDatetime() {
        return createdDatetime;
    }

    public void setCreatedDatetime(Date createdDatetime) {
        this.createdDatetime = createdDatetime;
    }

    public User getUserId() {
        return userId;
    }

    public void setUserId(User userId) {
        this.userId = userId;
    }

    public PostType getPostTypeId() {
        return postTypeId;
    }

    public void setPostTypeId(PostType postTypeId) {
        this.postTypeId = postTypeId;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (postId != null ? postId.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Post)) {
            return false;
        }
        Post other = (Post) object;
        if ((this.postId == null && other.postId != null) || (this.postId != null && !this.postId.equals(other.postId))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "entity.Post[ postId=" + postId + " ]";
    }

}

と

@Entity
@Table(name = "post_image")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "PostImage.findAll", query = "SELECT p FROM PostImage p"),
    @NamedQuery(name = "PostImage.findByPostImageId", query = "SELECT p FROM PostImage p WHERE p.postImageId = :postImageId"),
    @NamedQuery(name = "PostImage.findByPath", query = "SELECT p FROM PostImage p WHERE p.path = :path"),
    @NamedQuery(name = "PostImage.findByTitle", query = "SELECT p FROM PostImage p WHERE p.title = :title")})
public class PostImage implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @Column(name = "post_image_id")
    private Integer postImageId;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 500)
    @Column(name = "path")
    private String path;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 500)
    @Column(name = "title")
    private String title;
    @JoinColumn(name = "post_id", referencedColumnName = "post_id")
    @ManyToOne(optional = false)
    private Post postId;

    public PostImage() {
    }

    public PostImage(Integer postImageId) {
        this.postImageId = postImageId;
    }

    public PostImage(Integer postImageId, String path, String title) {
        this.postImageId = postImageId;
        this.path = path;
        this.title = title;
    }

    public Integer getPostImageId() {
        return postImageId;
    }

    public void setPostImageId(Integer postImageId) {
        this.postImageId = postImageId;
    }

    public String getPath() {
        return path;
    }

    public void setPath(String path) {
        this.path = path;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Post getPostId() {
        return postId;
    }

    public void setPostId(Post postId) {
        this.postId = postId;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (postImageId != null ? postImageId.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof PostImage)) {
            return false;
        }
        PostImage other = (PostImage) object;
        if ((this.postImageId == null && other.postImageId != null) || (this.postImageId != null && !this.postImageId.equals(other.postImageId))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "entity.PostImage[ postImageId=" + postImageId + " ]";
    }

}

Collection objPostImage = objPost.getPostImageCollection（）のような特定の投稿の画像のコレクションを取得したいのですが、多対多の関係ではこの機能が提供されません。1対多に変換する方法や投稿の画像コレクションを取得する方法を教えてください。私はJavaを初めて使用するので、助けや提案があれば、事前に感謝します...

4

2 に答える 2

0

これを試して：

@Entity
@Table(name = "post")
public class Post
{
    //....

    @OneToMany(mappedBy = "post")
    private Set<PostImage> images;

    //....
}

@Entity
@Table(name = "post_image")
public class PostImage
{
    //....

    @JoinColumn(name = "post_id", referencedColumnName = "id")
    @ManyToOne(optional = false)
    private Post post;

    //....
}

Seth の回答が機能しなかった理由は、EclipseLink がフィールドを使用して永続データにアクセスするためです。(Hibernate はプロパティ IIRC を使用します。) JPA プロバイダーがこのデータにアクセスする方法をクラスごとに指定できます。

フィールドの使用:

@Entity
@Access(AccessType.FIELD)
public class SomeEntity
{
    @Id
    private Long id;

    //....
}

プロパティの使用:

@Entity
@Access(AccessType.PROPERTY)
public class SomeEntity
{
    private Long id;

    //....

    @Id
    public Long getId()
    {
        return id;
    }
}

ただし、@Access(AccessType.PROPERTY)フィールドを使用する場合は(少なくともEclipseLinkでは)使用されるため、次のようなことが可能です:

@Entity
@Access(AccessType.PROPERTY)
public class SomeEntity
{
    private Long id;

    @Column(name = "text")
    private String someText;

    //....

    @Id
    public Long getId()
    {
        return id;
    }
}
于 2012-06-07T06:42:03.483 に答える
0

Post オブジェクトに PostImages の java.util.Set を追加し、Hibernate マッピングを使用して関係を提供できます。 このサイトには、1 対多の関係を設定する優れた例があります。

したがって、たとえば、次のようなものを Post クラスに追加する必要があります。

private Set<PostImage> postImages = new HashSet<PostImage>();

@OneToMany(fetch = FetchType.LAZY, mappedBy = "post")
public Set<PostImage> getPostImages() {
return this.postImages;
}

public void setPostImages(Set<PostImage> postImages) {
this.postImages= postImages;
}

次に、PostImage クラスで、Post オブジェクトへの参照を追加します。

private Post post;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "POST_ID", nullable = false)
public Stock getPost() {
return this.post;
}

public void setPost(Post post) {
this.post= post;
}

それを追加すると、Post オブジェクトで getPostImages() メソッドを呼び出すことができるようになります。

于 2012-06-05T17:19:24.187 に答える