java – Hibernate merge正在生成新行而不是更新

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我正在使用Hibernate-EntityManager版本4.3.5.我有多个表使用带有生成值的id.

插入等工作正常,但是当我尝试合并时,Hibernate不会更新旧行并创建新行.

内容相同,但id正在递增.

合并前：

合并后：

我尝试使用自定义Id生成器来检查Id是否已存在.有了这个新策略,我得到以下错误：

Caused by: java.sql.SQLException: Field 'product_id' doesn't have a default value
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1094)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4226)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4158)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2615)

编辑：

我发现@GeneratedValues不会在局部变量中设置id.这意味着您可以在合并时覆盖现有的那些.虽然,这并没有解决我的问题.

这是我正在使用的代码：

@Entity(name = "calculation_storage")
@Proxy(lazy = false)
public class CalculationStorage {

@Id
private Date created;

@OneToMany(mappedBy = "storage", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<Product> products;

public CalculationStorage(Date created) {
    this.created = created;
    this.products = new LinkedList<Product>() {
        @Override
        public boolean add(Product product) {
            product.setStorage(CalculationStorage.this);
            return super.add(product);
        }
    };
}

public CalculationStorage(Date created, List<Product> products) {
    this.created = created;
    this.products = products;
}

public CalculationStorage() {
}

public Date getCreated() {
    return created;
}

public void setCreated(Date created) {
    this.created = created;
}

/**
 * Durch das aufrufen get add Methode wird der benoetigte Fremdschluesseleintrag gesetzt
 *
 * @return Alle Produkte die registriert sind
 */
public List<Product> getProducts() {
    return products;
}

public void setProducts(List<Product> entities) {
    this.products = entities;
}

PRODUKT：

@Entity(name = "product")
public class Product implements Serializable {

@Id
@Column(name = "product_id")
//@GeneratedValue
@GeneratedValue(strategy=GenerationType.IDENTITY, generator="IdOrGenerated")
@GenericGenerator(name="IdOrGenerated",
        strategy="at.iktopia.firmenverwaltung.abendabrechnung.control.hibernate.ProductIdGenerator"
)
private int id;

private double costs;

private String name;

private ProductType type;

@OneToMany(mappedBy = "product", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<CalculatorEntity> entities;

@ManyToOne
@JoinColumn(name = "product_fk", nullable = false)
private CalculationStorage storage;

public Product(String name, ProductType type, double costs) {
    this.name = name;
    this.type = type;
    this.costs = costs;
    this.entities = new LinkedList<>();
}

/**
 * JPA - Konstruktor
 */
public Product() {
}

public int getId() {
    return id;
}

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

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public ProductType getType() {
    return type;
}

public void setType(ProductType type) {
    this.type = type;
}

public List<CalculatorEntity> getEntities() {
    return entities;
}

public void setEntities(List<CalculatorEntity> entities) {
    this.entities = entities;
}

public double getCosts() {
    return costs;
}

public void setCosts(double costs) {
    this.costs = costs;
}

public CalculationStorage getStorage() {
    return storage;
}

public void setStorage(CalculationStorage calculationStorage) {
    this.storage = calculationStorage;
}
}

发电机：

public class ProductIdGenerator extends IdentityGenerator {
@Override
public Serializable generate(SessionImplementor session, Object obj) throws HibernateException {
    if (obj == null) throw new HibernateException(new NullPointerException());

    if ((((Product) obj).getId()) == 0) return super.generate(session, obj);

    else return ((Product) obj).getId();
}
}

调用以合并对象的更新方法：

public class CalculationManager implements Manager<CalculationStorage, Date, CalculationStorageList> {

/**
 * @see Manager#save(Object)
 */
@Override
public void save(CalculationStorage calculationStorage) {
    Validate.notNull(calculationStorage);

    EntityManager em = PersistenceManager.getInstance().getEntityManager();
    EntityTransaction transaction = em.getTransaction();

    transaction.begin();

    try {
        em.persist(calculationStorage);
        transaction.commit();
    } catch (Exception e) {
        ErrorHandler.handleException(e, JPA_PERSIST_ERROR_MESSAGE);
        if (transaction.isActive())
            transaction.rollback();
    }

    em.close();
}

/**
 * @see Manager#update(Object)
 */
@Override
public void update(CalculationStorage calculations) {
    Validate.notNull(calculations);

    EntityManager em = PersistenceManager.getInstance().getEntityManager();
    EntityTransaction transaction = em.getTransaction();

    transaction.begin();

    try {
        CalculationStorage c = em.getReference(CalculationStorage.class, calculations.getCreated());
        c.setProducts(calculations.getProducts());

        em.merge(c);

        transaction.commit();
    } catch (EntityNotFoundException e) {
        if (transaction.isActive())
            transaction.rollback();
        save(calculations);
    } catch (Exception e) {
        ErrorHandler.handleException(e, JPA_PERSIST_ERROR_MESSAGE);
        if (transaction.isActive())
            transaction.rollback();
    }

    em.close();
}

/**
 * @see Manager#getAll()
 */
@Override
public CalculationStorageList getAll() {
    EntityManager em = PersistenceManager.getInstance().getEntityManager();

    List<CalculationStorage> calculations;

    try {
        calculations = em.createQuery("SELECT c FROM calculation_storage c").getResultList();
    } catch (Exception e) {
        ErrorHandler.handleException(e, JPA_LOAD_ERROR_MESSAGE);
        return null;
    }

    em.close();

    return new CalculationStorageList(calculations);
}

/**
 * @see Manager#remove(Object)
 */
@Override
public void remove(Date primaryKey) {
    Validate.notNull(primaryKey);

    EntityManager em = PersistenceManager.getInstance().getEntityManager();
    EntityTransaction transaction = em.getTransaction();

    transaction.begin();

    try {
        em.remove(em.getReference(CalculationStorage.class, primaryKey));
        transaction.commit();
    } catch (Exception e) {
        ErrorHandler.handleException(e, JPA_PERSIST_ERROR_MESSAGE);
        if (transaction.isActive())
            transaction.rollback();
    }

    em.close();
}

/**
 * @see Manager#get(Object)
 */
@Override
public CalculationStorage get(Date primaryKey) {
    Validate.notNull(primaryKey);

    EntityManager em = PersistenceManager.getInstance().getEntityManager();

    try {
        CalculationStorage storage = em.getReference(CalculationStorage.class, primaryKey);
        em.close();
        return storage;
    } catch (Exception e) {
        ErrorHandler.handleException(e, JPA_LOAD_ERROR_MESSAGE);
        return null;
    }
}
}

我无能为力导致这个问题.

解决方法:

试着看看：http://www.programmingforfuture.com/2011/02/hibernate-merge-may-insert-new-record.html

它可以帮助你.

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