Eclipselink JPA gets error when inserting into Derby table with generated primary key

问题

EclipseLink seems to be incorrectly passing a null primary key value to Derby when persisting into a table with generated primary key. Derby returns error of Attempt to modify an identity column in this case. Derby needs a SQL statement that excludes the id value. My question is how do I coerce EclipseLink to send the right SQL? Details follow...

I am using Eclipselink to map to a Derby database (v10.8.1.2) under the latest Netbeans 7.3beta2.

The database table primary key is auto generated:

CREATE TABLE STUDENT_BATCH ( 
    ID bigint PRIMARY KEY
        GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1),
    FILENAME varchar(200) NOT NULL,
    SCHOOLBOARD varchar(100) NOT NULL,
    CREATE_TS timestamp NOT NULL,
    CONTACT_INFO varchar(200),
    NOTES varchar(2000),
    BOARD_NAME varchar(100)
)
;

The corresponding jpa class specifies that the id is generated using strategy of identity:

@Entity
@Table(name = "STUDENT_BATCH")
@XmlRootElement
@NamedQueries({
@NamedQuery(name = "StudentBatch.findAll", query = "SELECT s FROM StudentBatch s")})
public class StudentBatch implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "ID")
    private Long id;
    @Basic(optional = false)
    @Column(name = "FILENAME")
    private String filename;
    @Basic(optional = false)
    @Column(name = "SCHOOLBOARD")
    private String schoolboard;
    @Basic(optional = false)
    @Column(name = "CREATE_TS")
    @Temporal(TemporalType.TIMESTAMP)
    private Date createTs;
    @Column(name = "CONTACT_INFO")
    private String contactInfo;
    @Column(name = "NOTES")
    private String notes;
    @Column(name = "BOARD_NAME")
    private String boardName;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "studentBatchId")
    private Collection<StudentRecord> studentRecordCollection;

    methods etc follow...

When I go to persist the class, I do not specify an id so that Derby will provide the id.

                StudentBatch sb = new StudentBatch();
                sb.setBoardName(meta.get("BOARD NAME"));
                sb.setContactInfo(meta.get("CONTACT INFO"));
                sb.setCreateTs(new Date());
                sb.setFilename(event.getFile().getFileName());
                sb.setNotes(meta.get("NOTES"));
                sb.setSchoolboard(meta.get("SCHOOL BOARD"));
                _logger.debug("persisting batch");
                em.persist(sb);
                _logger.debug("flushing");
                em.flush();
                _logger.debug("flushed");

Eclipselink, however, passes the id to derby as null and Derby gives error Attempt to modify an identity column:

INFO: DEBUG  11710 27 Nov 2012 18:17:10,558 [http-thread-pool-8080(4)] (FileUploadController.java:75) - persisting batch
INFO: DEBUG  11713 27 Nov 2012 18:17:10,561 [http-thread-pool-8080(4)] (FileUploadController.java:77) - flushing
WARNING: Local Exception Stack: 
Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLSyntaxErrorException: Attempt to modify an identity column 'ID'. 
Error Code: -1
Call: INSERT INTO STUDENT_BATCH (ID, BOARD_NAME, CONTACT_INFO, CREATE_TS, FILENAME, NOTES, SCHOOLBOARD) VALUES (?, ?, ?, ?, ?, ?, ?)
bind => [7 parameters bound]
Query: InsertObjectQuery(ca.ontario.mhltc.studentupload.model.StudentBatch[ id=null ])
at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:333)

This makes some sense to me since if I try to execute an insert on sql command line with the id field specified I get an error too.

INSERT INTO STUDENT_BATCH (id, BOARD_NAME, CONTACT_INFO, CREATE_TS, FILENAME, NOTES, SCHOOLBOARD)
VALUES (null, 'abc', 'def', current_timestamp, 'aaa', 'aabb', '1234');

gives me this:

Error code -1, SQL state 42Z23: Attempt to modify an identity column 'ID'. 
Line 1, column 1

Execution finished after 0 s, 1 error(s) occurred.

however, this insert statement is successful:

INSERT INTO STUDENT_BATCH (BOARD_NAME, CONTACT_INFO, CREATE_TS, FILENAME, NOTES, SCHOOLBOARD)
VALUES ('abc', 'def', current_timestamp, 'aaa', 'aabb', '1234');

returns

Executed successfully in 0.002 s, 1 rows affected.
Line 1, column 1

Execution finished after 0.002 s, 0 error(s) occurred.

Seems to me that Eclipselink should know about how Derby handles identity columns and should not pass the id column at all on the insert statement. Is there a workaround for this or I should I just dump Derby and use some other database?

回答1:

EclipseLink does not include the Id in the INSERT for Derby IDENTITY, so you have something odd going on.

Did you previously use another generator strategy and not recompile/deploy your code correctly?

Also try setting your platform using the"eclipselink.target-database"="Derby" in your persistence.xml.

来源：https://stackoverflow.com/questions/13595432/eclipselink-jpa-gets-error-when-inserting-into-derby-table-with-generated-primar