使用JPA和自动生成的主键在数据库中创建条目

Question

I am a Java EE/JPA newbie, currently attending a beginners course on Java EE programming.

I am trying to create new entries in a database which has a sequence defined for generating an ID, which is to be used as the primary key.

This is the Entity, which was generated by Eclipse from the database table:

@Entity
@Table(name = "ADDR_PROJ")
public class AddrProj implements Serializable
{
   private static final long serialVersionUID = 1L;

   @Id
   @SequenceGenerator(name = "ADDR_PROJ_ID_GENERATOR", sequenceName = "ADDR_SEQ")
   @GeneratedValue(strategy = GenerationType.SEQUENCE, generator =
"ADDR_PROJ_ID_GENERATOR")
   @Column(insertable = false, updatable = false)
   private long id;

   // ...
   // other fields
}

(BTW, long getId() is implemented, but void setId(long) is not.)

The table and sequence were created using the following SQL statements:

CREATE TABLE addr_proj (
    id           INTEGER PRIMARY KEY,
    name         VARCHAR(30),
    address      VARCHAR(30),
    birthday     DATE,
    email        VARCHAR(50),
    workphone    DECIMAL(4,0)
);

CREATE SEQUENCE addr_seq
START WITH 1
INCREMENT BY 1
NOMAXVALUE;

Manual insertions into the table work fine using statements like this:

INSERT INTO addr_proj VALUES
(
   addr_seq.nextval,
   'Matt',
   '3 Fake Ave, Madeuptown',
   '01-apr-1980',
   'matt@madeupemail.com',
   '1234'
);

However, when I try to update via the DAO, I get errors like the following:

Caused By: org.apache.openjpa.lib.jdbc.ReportingSQLException:
ORA-01400: cannot insert NULL into ("AJP05"."ADDR_PROJ"."ID")
{prepstmnt 28 INSERT INTO ADDR_PROJ (address, birthday, email, name,
workphone) VALUES (?, ?, ?, ?, ?) [params=(String) 43 Fake Ln, NotA
City, (Date) 1963-02-04, (String) pete@email.not, (String) Pete,
(BigDecimal) 1337]} [code=1400, state=23000]
   at org.apache.openjpa.lib.jdbc.LoggingConnectionDecorator.wrap(LoggingConnectionDecorator.java:192)
   at org.apache.openjpa.lib.jdbc.LoggingConnectionDecorator.access$700(LoggingConnectionDecorator.java:57)
   at org.apache.openjpa.lib.jdbc.LoggingConnectionDecorator$LoggingConnection$LoggingPreparedStatement.executeUpdate(LoggingConnectionDecorator.java:866)
   at org.apache.openjpa.lib.jdbc.DelegatingPreparedStatement.executeUpdate(DelegatingPreparedStatement.java:269)
   at org.apache.openjpa.jdbc.kernel.JDBCStoreManager$CancelPreparedStatement.executeUpdate(JDBCStoreManager.java:1421)
   Truncated. see log file for complete stacktrace

Note that the code is trying to insert 5 values, when 6 are required - the ID is missing.

The DAO code looks (something) like this:

void add(AddrProj item) {
    em.persist(item);
}

What's causing this problem?

Do I need a setId(long) method in my Entity class?

Do I need special code in the DAO's add() method to manage the sequence generator?

Am I missing something else?

Note: This is homework, but my choice to try using an auto-generated primary key was a bit beyond the scope of the assignment. It hasn't been covered in the course.

Answer 1

Remove @Column(insertable = false, updatable = false) and the column will be part of the insert and update.

Check the jpa hibernate annotation documentation section "2.2.2.3. Declaring column attributes".

http://docs.jboss.org/hibernate/annotations/3.5/reference/en/html_single/

insertable (optional): whether or not the column will be part of the insert statement (default true)
updatable (optional): whether or not the column will be part of the update statement (default true)