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Replies:
3
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Last Post:
Jan 23, 2006 8:13 AM
by: dibyendumajumdar
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Problem with @ManyToOne mapping
Posted:
Jan 16, 2006 7:44 AM
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Hi,
I am using the TPC-C benchmark schema definition for my experiments with EJB 3.0. I am trying to map the Warehouse and District tables. The Warehouse table has a single ID column as primary key, but the district table has a composite primary key that consists of an ID column and a warehouse ID column. Reproduced below is part of the SQL script to create the tables:
CREATE TABLE TPCC.WAREHOUSE (
W_ID INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1 ,INCREMENT BY 1),
CONSTRAINT PK_WAREHOUSE PRIMARY KEY(W_ID),
);
CREATE TABLE TPCC.DISTRICT (
D_ID INTEGER NOT NULL,
D_W_ID INTEGER NOT NULL,
CONSTRAINT PK_DISTRICT PRIMARY KEY(D_W_ID, D_ID),
CONSTRAINT FK_WAREHOUSE FOREIGN KEY(D_W_ID) REFERENCES TPCC.WAREHOUSE ( W_ID )
ON UPDATE RESTRICT ON DELETE RESTRICT
);
I have mapped these as follows (again an excerpt):
@Entity
@Table(name="WAREHOUSE", schema="TPCC")
public class Warehouse {
Long id;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="W_ID")
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
}
@Entity
@Table(name = "DISTRICT", schema = "TPCC")
@IdClass(schema1.entity.tpcc.District.DistrictPK.class)
public class District {
Warehouse warehouse;
Long id;
Long warehouseId;
@Id
@Column(name = "D_ID", nullable=false)
@GeneratedValue(strategy = GenerationType.TABLE, generator = "DISTRICT_ID_SEQUENCE")
@TableGenerator(name = "DISTRICT_ID_SEQUENCE", table = "IDGENERATOR", schema = "TPCC", pkColumnName = "SEQ_NAME", valueColumnName = "SEQ_COUNT", pkColumnValue = "DISTRICT_ID_SEQUENCE", allocationSize = 10)
public Long getId() {
return id;
}
@Id
@Column(name = "D_W_ID", nullable=false)
public Long getWarehouseId() {
return warehouseId;
}
@ManyToOne
@JoinColumn(name = "D_W_ID", referencedColumnName = "W_ID")
public Warehouse getWarehouse() {
return warehouse;
}
public void setWarehouseId(Long warehouseId) {
this.warehouseId = warehouseId;
}
public void setId(Long id) {
this.id = id;
}
public void setWarehouse(Warehouse warehouse) {
this.warehouse = warehouse;
this.warehouseId = warehouse.getId();
}
public static class DistrictPK {
Long id;
Long warehouseId;
public Long getId() {
return id;
}
public Long getWarehouseId() {
return warehouseId;
}
public void setId(Long id) {
this.id = id;
}
public void setWarehouseId(Long warehouseId) {
this.warehouseId = warehouseId;
}
@Override
public boolean equals(Object arg0) {
if (arg0 == this) {
return true;
} else if (arg0 instanceof DistrictPK) {
DistrictPK other = (DistrictPK) arg0;
return id.equals(other.id)
&& warehouseId.equals(other.warehouseId);
}
return false;
}
@Override
public int hashCode() {
return id.hashCode() ^ warehouseId.hashCode();
}
}
}
When I try to run a program, I am getting the following exception:
Exception [TOPLINK-48] (Oracle TopLink Essentials - 10g release 4 (10.1.4.0.0) (Build 060104Dev)): oracle.toplink.essentials.exceptions.DescriptorException
Exception Description: Multiple writable mappings exist for the field [TPCC.DISTRICT.D_W_ID]. Only one may be defined as writable, all others must be specified read-only.
Mapping: oracle.toplink.essentials.mappings.OneToOneMapping[warehouse]
Descriptor: RelationalDescriptor(schema1.entity.tpcc.District --> [DatabaseTable(TPCC.DISTRICT)])
Runtime Exceptions:
---------------------------------------------------------
at oracle.toplink.essentials.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:428)
at oracle.toplink.essentials.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:360)
at oracle.toplink.essentials.internal.sessions.DatabaseSessionImpl.postConnectDatasource(DatabaseSessionImpl.java:677)
at oracle.toplink.essentials.internal.sessions.DatabaseSessionImpl.login(DatabaseSessionImpl.java:572)
at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:160)
at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:100)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:59)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:48)
at schema1.cmdline.InsertWarehouse.main(InsertWarehouse.java:20)
Descriptor Exceptions:
---------------------------------------------------------
Local Exception Stack:
Exception [TOPLINK-48] (Oracle TopLink Essentials - 10g release 4 (10.1.4.0.0) (Build 060104Dev)): oracle.toplink.essentials.exceptions.DescriptorException
Exception Description: Multiple writable mappings exist for the field [TPCC.DISTRICT.D_W_ID]. Only one may be defined as writable, all others must be specified read-only.
Mapping: oracle.toplink.essentials.mappings.OneToOneMapping[warehouse]
Descriptor: RelationalDescriptor(schema1.entity.tpcc.District --> [DatabaseTable(TPCC.DISTRICT)])
at oracle.toplink.essentials.exceptions.DescriptorException.multipleWriteMappingsForField(DescriptorException.java:919)
at oracle.toplink.essentials.internal.descriptors.ObjectBuilder.initialize(ObjectBuilder.java:1817)
at oracle.toplink.essentials.descriptors.ClassDescriptor.initialize(ClassDescriptor.java:1786)
at oracle.toplink.essentials.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:399)
at oracle.toplink.essentials.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:360)
at oracle.toplink.essentials.internal.sessions.DatabaseSessionImpl.postConnectDatasource(DatabaseSessionImpl.java:677)
at oracle.toplink.essentials.internal.sessions.DatabaseSessionImpl.login(DatabaseSessionImpl.java:572)
at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:160)
at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:100)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:59)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:48)
at schema1.cmdline.InsertWarehouse.main(InsertWarehouse.java:20)
Any idea what this means?
Regards
Dibyendu
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Re: Problem with @ManyToOne mapping
Posted:
Jan 17, 2006 8:14 AM
in response to: dibyendumajumdar
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I reported this problem to the EJB spec people, and thanks to a reply from Mike Keith, the problem is resolved. I quote his reply here:
QUOTE
Although you have correctly mapped the warehouseId and the warehouse fields to the same column you need to make one of them read-only. Try mapping the warehouseId the following way:
@Id @Column(name="D_W_ID", nullable=false, insertable=false, updatable=false)
public Long getWarehouseId() { return warehouseId; }
ENDQUOTE
I made this change and it resolved the problem.
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