Hibernate n：m extractHashCode抛出NullPointerException

I get the following exception while inserting an object with hibernate. Reading from the database works like a charm. I use MySQL 5.5 as database provider and hibernate 3.6.5.

插入带有hibernate的对象时出现以下异常。从数据库中读取就像一个魅力。我使用MySQL 5.5作为数据库提供程序和hibernate 3.6.5。

I have the following database schema:

我有以下数据库架构:

cell(id,cellid,lac,mcc,mnc,insertTime)
location(id,latitude,longitude,altitude,accuracy,heading,hdop,vdop,pdop,insertTime)
cellatlocation(servingCell,neighbourCell,location,signalStrength,insertTime)

where id in cell and location are primary keys and servingCell,neighbourCell and location is the composite primary key in cellatlocation.

其中单元格和位置中的id是主键和servingCell,neighbourCell和location是cellatlocation中的复合主键。

java.lang.NullPointerException
at org.hibernate.type.descriptor.java.AbstractTypeDescriptor.extractHashCode(AbstractTypeDescriptor.java:88)
at org.hibernate.type.AbstractStandardBasicType.getHashCode(AbstractStandardBasicType.java:196)
at org.hibernate.type.AbstractStandardBasicType.getHashCode(AbstractStandardBasicType.java:191)
at org.hibernate.type.EntityType.getHashCode(EntityType.java:325)
at org.hibernate.type.ComponentType.getHashCode(ComponentType.java:222)
at org.hibernate.engine.EntityKey.generateHashCode(EntityKey.java:126)
at org.hibernate.engine.EntityKey.<init>(EntityKey.java:70)
at org.hibernate.engine.StatefulPersistenceContext.getDatabaseSnapshot(StatefulPersistenceContext.java:286)
at org.hibernate.engine.ForeignKeys.isTransient(ForeignKeys.java:211)
at org.hibernate.event.def.AbstractSaveEventListener.getEntityState(AbstractSaveEventListener.java:531)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:103)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
at org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:685)
at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:677)
at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:673)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:345)
at $Proxy17.saveOrUpdate(Unknown Source)

The classes I want to insert: Cell.java

我要插入的类:Cell.java

@Entity
@Table(name = "cell", catalog = "crisis")
public class Cell implements Serializable {

private static final long serialVersionUID = -8532796958180260393L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private Integer mnc;
private Integer mcc;
private Long cellid;
private Integer lac;
@org.hibernate.annotations.Type(type = "org.joda.time.contrib.hibernate.PersistentDateTime")
private DateTime insertTime;
@OneToMany(mappedBy = "pk.servingCell")
private List<CellAtLocation> cellAtLocation = new LinkedList<CellAtLocation>();

public Long getId() {
    return id;
}

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

public Integer getMnc() {
    return mnc;
}

public void setMnc(Integer mnc) {
    this.mnc = mnc;
}

public Integer getMcc() {
    return mcc;
}

public void setMcc(Integer mcc) {
    this.mcc = mcc;
}

public Long getCellid() {
    return cellid;
}

public void setCellid(Long cellid) {
    this.cellid = cellid;
}

public Integer getLac() {
    return lac;
}

public void setLac(Integer lac) {
    this.lac = lac;
}

public DateTime getInsertTime() {
    return insertTime;
}

public void setInsertTime(DateTime insertTime) {
    this.insertTime = insertTime;
}

public List<CellAtLocation> getCellAtLocation() {
    return cellAtLocation;
}

public void setCellAtLocation(List<CellAtLocation> cellAtLocation) {
    this.cellAtLocation = cellAtLocation;
}
}

Location.java

@Entity
@Table(name = "location", catalog = "crisis")
public class Location implements Serializable {

private static final long serialVersionUID = 2197290868029835453L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private Double latitude;
private Double longitude;
private Double altitude;
private Double accuracy;
private Double heading;
private Double hdop;
private Double vdop;
private Double pdop;
@org.hibernate.annotations.Type(type = "org.joda.time.contrib.hibernate.PersistentDateTime")
private DateTime insertTime;

@OneToMany(mappedBy = "pk.location")
private List<CellAtLocation> cellAtLocation = new LinkedList<CellAtLocation>();

public Long getId() {
    return id;
}

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

public Double getLatitude() {
    return latitude;
}

public void setLatitude(Double latitude) {
    this.latitude = latitude;
}

public Double getLongitude() {
    return longitude;
}

public void setLongitude(Double longitude) {
    this.longitude = longitude;
}

public Double getAltitude() {
    return altitude;
}

public void setAltitude(Double altitude) {
    this.altitude = altitude;
}

public Double getAccuracy() {
    return accuracy;
}

public void setAccuracy(Double accuracy) {
    this.accuracy = accuracy;
}

public Double getHeading() {
    return heading;
}

public void setHeading(Double heading) {
    this.heading = heading;
}

public Double getHdop() {
    return hdop;
}

public void setHdop(Double hdop) {
    this.hdop = hdop;
}

public Double getVdop() {
    return vdop;
}

public void setVdop(Double vdop) {
    this.vdop = vdop;
}

public Double getPdop() {
    return pdop;
}

public void setPdop(Double pdop) {
    this.pdop = pdop;
}

public DateTime getInsertTime() {
    return insertTime;
}

public void setInsertTime(DateTime insertTime) {
    this.insertTime = insertTime;
}

public List<CellAtLocation> getCellAtLocation() {
    return cellAtLocation;
}

public void setCellAtLocation(List<CellAtLocation> cellAtLocation) {
    this.cellAtLocation = cellAtLocation;
}

}

CellAtLocation.java

@Entity
@Table(name = "cellatlocation", catalog = "crisis")
@AssociationOverrides({ @AssociationOverride(name = "pk.servingCell", joinColumns = @JoinColumn(name = "servingCell")),
    @AssociationOverride(name = "pk.neighbourCell", joinColumns = @JoinColumn(name = "neighbourCell")),
    @AssociationOverride(name = "pk.location", joinColumns = @JoinColumn(name = "location")) })

public class CellAtLocation implements Serializable {
private static final long serialVersionUID = -4440795783726362367L;
private CellAtLocationPk pk = new CellAtLocationPk();
private Integer signalStrength;

@EmbeddedId
private CellAtLocationPk getPk() {
    return pk;
}

@SuppressWarnings("unused")
private void setPk(CellAtLocationPk pk) {
    this.pk = pk;
}

@Transient
public Cell getServingCell() {
    return getPk().getServingCell();
}

public void setServingCell(Cell cell) {
    getPk().setServingCell(cell);
}

@Transient
public Cell getNeighbourCell() {
    return getPk().getNeighbourCell();
}

public void setNeighbourCell(Cell cell) {
    getPk().setNeighbourCell(cell);
}

@Transient
public Location getLocation() {
    return getPk().getLocation();
}

public void setLocation(Location location) {
    getPk().setLocation(location);
}

public Integer getSignalStrength() {
    return signalStrength;
}

public void setSignalStrength(Integer signalStrength) {
    this.signalStrength = signalStrength;
}

public boolean equals(Object o) {
    if (this == o)
        return true;
    if (o == null || getClass() != o.getClass())
        return false;
    CellAtLocation that = (CellAtLocation) o;
    if (getPk() != null ? !getPk().equals(that.getPk()) : that.getPk() != null)
        return false;
    return true;
}

public int hashCode() {
    return (getPk() != null ? getPk().hashCode() : 0);
}
}

and finally the primary key mapping itself CellAtLocationPk.java

最后是主键映射本身的CellAtLocationPk.java

@Embeddable
public class CellAtLocationPk implements Serializable {
private static final long serialVersionUID = 5286485161491158083L;
private Cell servingCell;
private Cell neighbourCell;
private Location location;

@ManyToOne
public Cell getServingCell() {
    return servingCell;
}

public void setServingCell(Cell servingCell) {
    this.servingCell = servingCell;
}

@ManyToOne
public Cell getNeighbourCell() {
    return neighbourCell;
}

public void setNeighbourCell(Cell neighbourCell) {
    this.neighbourCell = neighbourCell;
}

@ManyToOne
public Location getLocation() {
    return location;
}

public void setLocation(Location location) {
    this.location = location;
}

public boolean equals(Object o) {
    if (this == o)
        return true;
    if (o == null || getClass() != o.getClass())
        return false;
    CellAtLocationPk that = (CellAtLocationPk) o;
    if (servingCell != null ? !servingCell.equals(that.servingCell) : that.servingCell != null)
        return false;
    if (neighbourCell != null ? !neighbourCell.equals(that.neighbourCell) : that.neighbourCell != null)
        return false;
    if (location != null ? !location.equals(that.location) : that.location != null)
        return false;

    return true;
}

public int hashCode() {
    int result;
    result = (servingCell != null ? servingCell.hashCode() : 0);
    result = 31 * result + (neighbourCell != null ? neighbourCell.hashCode() : 0);
    result = 31 * result + (location != null ? location.hashCode() : 0);
    return result;
}
}

3 个解决方案

#1

The problem is that hibernate is trying to save the relationship object, CellAtLocation instance, while the children objects, Cell and/or Location instances are not yet persisted. Thus, children objects don't have generated ids associated with them and therefore hibernate can not compute the hash for them.

问题是hibernate正在尝试保存关系对象CellAtLocation实例,而子对象,Cell和/或Location实例尚未保留。因此,子对象没有生成与它们关联的id,因此hibernate无法计算它们的哈希值。

Before trying to save CellAtLocation instance, try saving the children objects first by calling saveOrUpdate method on them.

在尝试保存CellAtLocation实例之前,首先尝试通过对它们调用saveOrUpdate方法来保存子对象。

#2

For anyone also dealing with this issue, it occurred in my case simply because I did not have an open and active transaction. The stack trace did not point directly to this being the issue but can be explained as follows:

对于任何处理这个问题的人来说,只是因为我没有开放和活跃的交易。堆栈跟踪没有直接指出这是问题,但可以解释如下:

The parent item was being persisted in the cache and hibernate simply accepted the parent not having an actual ID. If we could have somehow called flush() on our connection we would have then been notified of the non-existent transaction. Instead, when the child item was to be persisted the parent's ID did not TRULY exist. When hibernate went to get the parent's hashed id for the purpose of saving the child, the NPE was thrown.

父项目被持久化在缓存中,而hibernate只是接受了没有实际ID的父项。如果我们可以以某种方式在我们的连接上调用flush(),那么我们就会被告知不存在的事务。相反,当要保留子项时,父项的ID不存在TRULY。当hibernate为了保存孩子而获得父亲的哈希id时,NPE被抛出。

#3

In my case, found out that one primary key in a foreign key table has not set. Only the fields that implement hashcode int the table were set.

在我的例子中,发现外键表中的一个主键没有设置。仅设置了在表中实现hashcode的字段。