在OneToMany中使用Hibernate持久化对象

Question

我的休眠级联有问题。 我正在尝试保留一组文档。 数据模型如下：

• 语料库1 --- n文档1 --- n TextBlock n --- 1演讲者n- 1派对

我的情况如下：

SpeakerFacade sf = new SpeakerFacade();
TextBlockFacade tf = new TextBlockFacade();

Corpus corpus = new Corpus();

Document doc1 = new Document(corpus);
TextBlock tb1 = new TextBlock(new Speaker("David", "Müller", new Party("ASDF")), "TB1", doc1);
tf.createTextBlock(tb1);
TextBlock tb2 = new TextBlock(new Speaker("Benedikt", "Müller", new Party("JKLÖ")), "TB2", doc1);
tf.createTextBlock(tb2);
TextBlock tb3 = new TextBlock(sf.findPersonById(1), "TB3", doc1);
tf.createTextBlock(tb3);

因此，在第一步中，我创建了一个新的TextBlock。 对于级联，其余的也应创建。 在第二个块中，我在同一文档中创建另一个文本块。 在最后一个块中，我还创建了另一个文本块，但使用了相同的扬声器。 但是我不断收到以下异常：

Caused by: org.hibernate.TransientPropertyValueException: object references an unsaved transient instance - save the transient instance before flushing : de.uniba.speechanalyser.persist.model.Document.corpus -> de.uniba.speechanalyser.persist.model.Corpus

在这里，您可以看到我的模型类（简写形式）：

语料库类

@Entity
public class Corpus implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
@Column(name = "corpus_id")
private int id;

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "corpus")
private List<Document> documentList;
}

文件类别

@Entity
public class Document implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
@Column(name = "document_id")
private int id;

@ManyToOne(cascade = { CascadeType.MERGE },fetch= FetchType.EAGER)
private Corpus corpus;

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "document")
private List<TextBlock> textBlockList;
}

TextBlock类

@Entity
public class TextBlock implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
@Column(name = "textblock_id")
private int id;

@Lob
String content;

@ManyToOne(cascade = { CascadeType.MERGE },fetch= FetchType.EAGER)
private Document document;

@ManyToOne(cascade = { CascadeType.MERGE },fetch= FetchType.EAGER)
private Speaker speaker;
}

演讲者班

@Entity
@NamedQueries({
    @NamedQuery(name = "Speaker.findSpeakerByName", query = "select s from Speaker s where s.firstName = :firstName and s.lastName = :lastName") })
public class Speaker implements Serializable {

private static final long serialVersionUID = 1L;
public static final String FIND_BY_NAME = "Speaker.findSpeakerByName";

@Id
@GeneratedValue
@Column(name = "speaker_id")
private int id;

private String firstName;
private String lastName;

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "speaker")
private List<TextBlock> textBlock;

@ManyToOne(cascade = { CascadeType.MERGE },fetch= FetchType.EAGER)
private Party party;
}

派对班

@Entity
@NamedQueries({
@NamedQuery(name = "Party.findPartyByName", query = "select p from Party p where p.name = :name")
})

public class Party implements Serializable {

private static final long serialVersionUID = 1L;
public static final String FIND_BY_NAME = "Party.findPartyByName";

@Id
@GeneratedValue
@Column(name = "party_id")
private int id;

private String name;

@OneToMany(cascade = { CascadeType.ALL}, mappedBy = "party")
private List<Speaker> speakerList;
}

我也为对象/表之间的关系而苦恼。 特别是与小瀑布。 我在stackoverflow上读了很多书，但没有任何帮助。 这是我目前的做法。 当自己创建每个对象时，就像这样：

Speaker speaker= new Speaker("David", "Müller", pf.findById(1));
sf.createSpeaker(speaker);
speaker = sf.findSpeakerById(1);

然后将其添加到TextBlock，它可以正常工作。 那有人可以帮我吗？

大卫问候

Answer 1

您的Corpus不会持续存在。 您只能级联MERGE。 请参阅Document类中的注释定义：

@ManyToOne(cascade = { CascadeType.MERGE }, fetch= FetchType.EAGER)
private Corpus corpus;

应该：

@ManyToOne(cascade = { CascadeType.MERGE, CascadeType.PERSIST }, fetch= FetchType.EAGER)
//you can simply say CascadeType.ALL if you are sure what you are doing
private Corpus corpus;

Answer 2

好的，很酷，我将问题缩小到关系的议长方。

我实际的新课程是： 语料库课程

@Entity
public class Corpus implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
@Column(name = "corpus_id")
private int id;

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "corpus")
private List<Document> documentList = new ArrayList<Document>();

public void addDocument(Document document) {
    if (documentList != null) {
        documentList.add(document);
    }
}
}

文件类别

@Entity
public class Document implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
@Column(name = "document_id")
private int id;

@ManyToOne
@JoinColumn(name = "corpus_id")
private Corpus corpus;

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "document")
private List<TextBlock> textBlockList = new ArrayList<TextBlock>();

public Document() {

}

public Document(Corpus corpus) {
    this.corpus = corpus;
}

public void addTextBlock(TextBlock textBlock) {
    if (textBlockList != null) {
        textBlockList.add(textBlock);
    }
}
}

TextBlock类

@Entity

public class TextBlock implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
@Column(name = "textblock_id")
private int id;

@Lob
String content;

@ManyToOne
@JoinColumn(name = "document_id")
private Document document;

@ManyToOne
private Speaker speaker;

public TextBlock() {

}

public TextBlock(Speaker speaker, String content, Document document) {
    this.speaker = speaker;
    this.content = content;
    this.document = document;
}
}

演讲者班

@Entity
@NamedQueries({
    @NamedQuery(name = "Speaker.findSpeakerByName", query = "select s from Speaker s where s.firstName = :firstName and s.lastName = :lastName") })

public class Speaker implements Serializable {

private static final long serialVersionUID = 1L;
public static final String FIND_BY_NAME = "Speaker.findSpeakerByName";

@Id
@GeneratedValue
@Column(name = "speaker_id")
private int id;

private String firstName;
private String lastName;

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "speaker")
private List<TextBlock> textBlock;

@ManyToOne
private Party party;

public Speaker() {

}

public Speaker(String firstName, String lastName, Party party) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.party = party;
}
}

派对班

@Entity
@NamedQueries({
@NamedQuery(name = "Party.findPartyByName", query = "select p from Party p where p.name = :name")})

public class Party implements Serializable {

private static final long serialVersionUID = 1L;
public static final String FIND_BY_NAME = "Party.findPartyByName";

@Id
@GeneratedValue
@Column(name = "party_id")
private int id;

private String name;

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "party")
private List<Speaker> speakerList = new ArrayList<Speaker>();

public Party() {

}

public Party(String name) {
    this.name = name;
}
}

我如何在“演讲者和聚会”上设置CascadeType，当我保留语料库时，“演讲者和聚会”也保持不变。

我的测试代码如下：

CorpusFacade cf = new CorpusFacade();

Corpus corpus = new Corpus();
Document document = new Document(corpus);
corpus.addDocument(document);

Party party = new Party("ASDF");
Speaker speaker = new Speaker("David", "Müller", party);

TextBlock textBlock1 = new TextBlock(speaker, "TB1", document);
document.addTextBlock(textBlock1);
TextBlock textBlock2 = new TextBlock(speaker, "TB1", document);
document.addTextBlock(textBlock2);

cf.createCorpus(corpus);

编辑对于那些对我的问题感兴趣的人。 我首先创建一个新的演讲者和一个新的聚会。 然后我坚持党（议长自动坚持）。 之后，我将Speaker添加到TextBlock。 就这样。 我找不到一个解决方案，即语料库也创建了演讲者和聚会。 我希望它对某人有用。