[Middlegen-user] using xdoclet to have cmp auto-generate primary key values

[Mike Wertheim]

This may seem like an odd request, but here goes...

I'm using JBoss 3.2.3 with PostgreSQL 7.3.2, and I have a CMP entity bean
(coded using ejbdoclet) that has an integer primary key. The ejbCreate code
currently generates the value for the primary key by doing a "select max(id)
from table", which is really slow because it has to access the database
twice (the select and the insert).

I understand that it's possible to have the entity bean use the database to
auto-generate new primary key values. (With postgres, it has been
recommended to use a database sequence to generate the values.)

Supposedly it's possible to do this in ejbdoclet, but I can't find any
reasonable documentation or an example to copy. I then discovered that
Middlegen can generate the ejbdoclet file for me. I downloaded Middlegen
and have been unsuccessful in getting it working in my environment.

But my ultimate goal isn't to get Middlegen running. All I want is an
example ejbdoclet file for a CMP entity bean that has its primary key value
auto-generated by a PostgreSQL sequence.

Following is the source code for the entity bean. Could someone show me how
to change it so that the primary key value is auto-generated by a PostgreSQL
sequence? Or, could someone email me an xdoclet file of some other CMP
entity bean that uses a PostgreSQL sequence to generate the primary key
value?


Thanks,
Mike


--------- ejbdoclet file follows ---------



import javax.ejb.*;
import java.sql.*;


/**
* @ejb.bean name="Item"
* jndi-name="Item"
* local-jndi-name="ItemLocal"
* type="CMP" cmp-version="2.x"
* view-type="both"
*
* @ejb.home remote-class="com.blah.ejb.entity.item.ItemHome"
* local-class="com.blah.ejb.entity.item.ItemLocalHome"
*
*
* @ejb.interface remote-class="com.blah.ejb.entity.item.Item"
* local-class="com.blah.ejb.entity.item.ItemLocal"
*
* @ejb.persistence table-name="Item"
*
* @jboss.persistence create-table="false" remove-table="false"
*
* @ejb.transaction type="Required"
*
* @ejb.pk class="com.blah.ejb.entity.item.ItemPK"
*
*/

public abstract class ItemEJB implements EntityBean {

protected EntityContext entityContext = null;


///////////////////////////////////////////////////////
// Container Managed Persistent Fields
///////////////////////////////////////////////////////

/**
* @ejb.interface-method view-type="both"
* @ejb.persistence column-name="itemID"
* @ejb:pk-field
*/
public abstract int getItemID();

/**
* @ejb.interface-method view-type="both"
* @ejb.persistence column-name="itemID"
*/
public abstract void setItemID(int itemID);


/**
* @ejb.interface-method view-type="both"
* @ejb.persistence column-name="name"
*/
public abstract String getName();

/**
* @ejb.interface-method view-type="both"
* @ejb.persistence column-name="name"
*/
public abstract void setName(String name);


///////////////////////////////////////////////////////
// Create methods
///////////////////////////////////////////////////////

/**
* @ejb.create-method view-type="both"
*/
public ItemPK ejbCreate(String name) throws CreateException {
synchronized(Item.class) {
int itemID = 0;

Connection con = null;
PreparedStatement ps = null;
try {
con = JNDICache.getConnection();
ps = con.prepareStatement("select MAX(ItemID) from ITEM");
ResultSet rs = ps.executeQuery();
rs.next();
itemID = rs.getInt(1) + 1;
rs.close();
}
catch (SQLException se) {
}
finally {
ps.close(); on.close();
}

setItemID(itemID);
setName(name);

return new ItemPK(itemID);
}
}

public void ejbPostCreate(String name) {
}


///////////////////////////////////////////////////////
// Other required methods
///////////////////////////////////////////////////////

public void setEntityContext(EntityContext ec) {
entityContext = ec;
}

public void unsetEntityContext() {
entityContext = null;
}

public void ejbActivate() { }
public void ejbPassivate() { }
public void ejbLoad() { }
public void ejbStore() { }
public void ejbRemove() { }
}

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