java - 新しいエンティティが永続化されないのはなぜですか?

Question

エンティティをインスタンス化して永続化するにはNoResultExceptionどうすればよいですか?Newsgroup

package net.bounceme.dur.usenet.driver;

import java.util.logging.Logger;
import javax.mail.Folder;
import javax.mail.Message;
import javax.persistence.*;
import net.bounceme.dur.usenet.model.Article;
import net.bounceme.dur.usenet.model.Newsgroup;

class DatabaseUtils {

    private static final Logger LOG = Logger.getLogger(DatabaseUtils.class.getName());
    private EntityManagerFactory emf = Persistence.createEntityManagerFactory("USENETPU");
    private EntityManager em = emf.createEntityManager();

    public void persistArticle(Message message, Folder folder) {
        //do all the persistence here?
        String fullNewsgroupName = folder.getFullName();
        Newsgroup newsgroup = null;
        TypedQuery<Newsgroup> query = em.createQuery("SELECT n FROM Newsgroup n WHERE n.newsgroup = :newsGroupParam", Newsgroup.class);
        query.setParameter("newsGroupParam", fullNewsgroupName);
        try {
            newsgroup = query.getSingleResult();
            LOG.info("found " + query.getSingleResult()); //ok
        } catch (javax.persistence.NoResultException e) {
            LOG.info(e + "\ncould not find " + fullNewsgroupName); //ok
            newsgroup = new Newsgroup(folder);
            //it seems like the persist statement never executes...
            em.persist(newsgroup);
        } catch (NonUniqueResultException e) {
            LOG.info("\nshould never happen\t" + fullNewsgroupName); //not ok, should never execute
        }
        //need some mechanism to ensure that newsgroup is never a null reference
        Article article = new Article(message, newsgroup);
        em.persist(article); //never seems to execute..
    }

    public void close() {
        em.close();
        emf.close();//necessary?
    }
}

さて、何度も何度も、クエリの結果が見つからないようです:

run:
DEBUG: nntp: newsrc loading /home/thufir/.newsrc
DEBUG: nntp: newsrc load: 5 groups in 30ms
Aug 03, 2012 6:04:47 PM net.bounceme.dur.usenet.driver.FetchBean <init>
INFO: [gwene.com.androidcentral, gwene.com.blogspot.emacsworld, gwene.com.blogspot.googlecode, gwene.com.blogspot.googlereader, gwene.com.economist]
[EL Info]: 2012-08-03 18:04:51.277--ServerSession(28034142)--EclipseLink, version: Eclipse Persistence Services - 2.3.0.v20110604-r9504
[EL Info]: 2012-08-03 18:04:52.417--ServerSession(28034142)--file:/home/thufir/NetBeansProjects/USENET/build/classes/_USENETPU login successful
[EL Warning]: 2012-08-03 18:04:52.557--ServerSession(28034142)--Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'usenet.ARTICLE' doesn't exist
Error Code: 1146
Call: ALTER TABLE ARTICLE DROP FOREIGN KEY FK_ARTICLE_NEWSGROUP_ID
Query: DataModifyQuery(sql="ALTER TABLE ARTICLE DROP FOREIGN KEY FK_ARTICLE_NEWSGROUP_ID")
[EL Warning]: 2012-08-03 18:04:52.572--ServerSession(28034142)--Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown table 'ARTICLE'
Error Code: 1051
Call: DROP TABLE ARTICLE
Query: DataModifyQuery(sql="DROP TABLE ARTICLE")
[EL Warning]: 2012-08-03 18:04:52.65--ServerSession(28034142)--Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown table 'NEWSGROUP'
Error Code: 1051
Call: DROP TABLE NEWSGROUP
Query: DataModifyQuery(sql="DROP TABLE NEWSGROUP")
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.androidcentral
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.androidcentral
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.androidcentral
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.androidcentral
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.androidcentral
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.androidcentral
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.androidcentral
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.androidcentral
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.emacsworld
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.googlecode
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.googlecode
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.googlecode
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.googlecode
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.googlecode
Aug 03, 2012 6:04:54 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.googlecode
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
[EL Info]: 2012-08-03 18:04:55.344--ServerSession(28034142)--file:/home/thufir/NetBeansProjects/USENET/build/classes/_USENETPU logout successful
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.googlecode
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.blogspot.googlecode
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.economist
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.economist
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.economist
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.economist
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.economist
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.economist
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.economist
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.DatabaseUtils persistArticle
INFO: javax.persistence.NoResultException: getSingleResult() did not retrieve any entities.
could not find gwene.com.economist
Aug 03, 2012 6:04:55 PM net.bounceme.dur.usenet.driver.FetchBean <init>
INFO: **************************done
BUILD SUCCESSFUL (total time: 11 seconds)

Newsgroup一意が存在しない場合、新しいエンティティがデータベースに永続化されるようにするにはどうすればよいですか? 結果ではないにしても、少なくともそれがコードの意図です。

ニュースグループ:

package net.bounceme.dur.usenet.model;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
import java.util.logging.Logger;
import javax.mail.Folder;
import javax.persistence.*;

@Entity
public class Newsgroup implements Serializable {

    private static final long serialVersionUID = 1L;
    private static final Logger LOG = Logger.getLogger(Newsgroup.class.getName());
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column //@Unique @UniqueConstraint interface..?
    private String newsgroup;
    @OneToMany(mappedBy = "newsgroup", cascade = CascadeType.PERSIST)
    private Set<Article> articles = new HashSet<>();

    public Newsgroup() {
        //should not create a newsgroup without a Folder
    }

    public Newsgroup(Folder folder) {
        newsgroup = folder.getFullName();//if row already exists, then what?
        LOG.fine(newsgroup);    
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.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 Newsgroup)) {
            return false;
        }
        Newsgroup other = (Newsgroup) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return newsgroup;
    }
}

および記事:

package net.bounceme.dur.usenet.model;

import java.io.Serializable;
import java.util.logging.Logger;
import javax.mail.Message;
import javax.persistence.*;

@Entity
public class Article implements Serializable {

    private static final long serialVersionUID = 1L;
    private static final Logger LOG = Logger.getLogger(Article.class.getName());
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column
    private int messageNumber;
    @ManyToOne(cascade = CascadeType.PERSIST)
    private Newsgroup newsgroup;

    public Article() {
    }

    public Article(Message message, Newsgroup newsgroup) {
        messageNumber = message.getMessageNumber();
        this.newsgroup = newsgroup;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.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 Article)) {
            return false;
        }
        Article other = (Article) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "\nmessageNumber\t" + messageNumber;
    }

    public int getMessageNumber() {
        return messageNumber;
    }

    public void setMessageNumber(int messageNumber) {
        this.messageNumber = messageNumber;
    }
}

score 2 · Accepted Answer

「Pro JPA 2」で Keith と Schinkariol を引用すると、次のようになります。

トランザクションが存在しない場合、変更操作で例外がスローされるか、変更がデータストアに永続化されません。

を使用して永続化する対話がEntityManager emトランザクションのコンテキスト内にあることを確認します。

public void persistArticle(Message message, Folder folder) {
    em.getTransaction().begin();
    try {
        // your code goes here; possibly current body of persistArticle(..)

        em.getTransaction().commit();
    } catch (final RuntimeException e) {
        if (em.getTransaction().isActive()) {
            em.getTransaction().rollback();
        }

        throw e;
    }
}

これが一般的な定型コードであることがすぐにわかります。デコレータの使用を検討してください:

によって提供されるサービス/メソッドを定義するインターフェイスを作成しますDatabaseUtils。
DatabaseUtilsそのインターフェースを実装しましょう。
DataUtilsServicesインターフェイスを実装する (デコレータ) を作成します。その実装には、トランザクションを管理するコードが含まれます。ここで、作業コード (「あなたのコードはここに入ります」) は、のインスタンスで同じメソッドへの呼び出しになりますDatabaseUtils。

現在、デコレーターを使用して「ワーカー」を「トランザクションサービス」から分離することで、Java EE、Spring、またはトランザクションを管理するその他のコンテナーフレームワークに将来簡単にステップインできるようになります。たとえば、DatabaseUtilsServicesボイラープレートをすべて含めると、EJB デコレーターの一部になる可能性が非常に高くなります。

@Override
@TransactionAttribute(TransactionAttributeType.REQUIRED)
public void persistArticle(Message message, Folder folder) {
    return databaseUtils.persistArticle(message, folder);
}

score 0 · Accepted Answer

おそらく、新しい Article をインスタンス化する行の直前に次の行を挿入するだけで十分でしょう:

if (newsgroup==null) {
    newsgroup = new NewsGroup();
}

また、Article から Newsgroup へのリレーションの Cascade プロパティが PERSIST に設定されていない場合、その新しい Newsgroup を手動で persist() する必要がある場合があります。

java - 新しいエンティティが永続化されないのはなぜですか?

3 に答える 3

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