java - Hibernate 合并正在生成新行而不是更新

java - Hibernate merge is generating new rows instead of updating

提问by EXSolo

I am using Hibernate-EntityManager version 4.3.5. I have multiple tables using an id with a generated value.

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

Inserting and such works fine, but when I try to merge Hibernate does not update the old rows and creates new ones.

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

The content is the same, but the id is incrementing.

内容是一样的，但是id是递增的。

Before merge:

合并前：

After merge:

合并后：

I tried to use a custom Id generator to check if the Id already exists. With this new strategy i get the following error:

我尝试使用自定义 Id 生成器来检查 Id 是否已存在。使用这个新策略，我收到以下错误：

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)

EDIT:

编辑：

I found out that @GeneratedValues will not set the ids in the local variables. That means that you might override the existing ones while merging. Though, that did not solve my problem.

我发现 @GeneratedValues 不会在局部变量中设置 ID。这意味着您可能会在合并时覆盖现有的。虽然，这并没有解决我的问题。

Here is the code I am using:

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:

产品：

@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;
}
}

The Generator:

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();
}
}

The update method that is called to merge the object:

为合并对象而调用的更新方法：

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;
    }
}
}

I am clueless what could cause this issue.

我不知道是什么导致了这个问题。

回答by EXSolo

Alright, I found the solution. Thanks a lot to Kulbhushan Singh who made me find out about this:

好的，我找到了解决方案。非常感谢 Kulbhushan Singh，他让我知道了这一点：

I am using @GeneratedValuein my code:

我@GeneratedValue在我的代码中使用：

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

What I didn't know is that when using @GeneratedValueonly the database entries get a ID. The local objects will have the same ID as before. (0 by default). In my case that would mean that product_idin the database was 1, 2, 3, ... and in my objects it was 0.

我不知道的是，当@GeneratedValue仅使用数据库条目时会获得一个 ID。本地对象将具有与以前相同的 ID。（默认为 0）。在我的情况下，这意味着product_id在数据库中是 1、2、3，......而在我的对象中它是 0。

When I tried to update my object I did the following:

当我尝试更新我的对象时，我执行了以下操作：

CalculationStorage dbReference = em.getReference(CalculationStorage.class, calculations.getCreated());
dbReference.setProducts(localStorageObject.getProducts());

I basically set the generated Ids from the database back to 0, because the Id was still 0 in my local object.

我基本上将数据库中生成的 Id 设置回 0，因为 Id 在我的本地对象中仍然是 0。

And because of me setting the Id back to 0, the database generated new Ids.

由于我将 Id 设置回 0，数据库生成了新的 Id。

EDIT: Obviously, if you restart your application the local id values will be 0 again. So try to pull the data from the db when you need it and let the Garbage Collector have it when you are done.

编辑：显然，如果您重新启动应用程序，本地 id 值将再次为 0。因此，请尝试在需要时从数据库中提取数据，并在完成后让垃圾收集器拥有它。