Hi,
I can tell the following on Read-ahead strategies.
By default a find-method returns only the primary keys of the records from the DB.
(SELECT PK FROM TABLE T; is carried out). Once you invoke a method of a single CMP-EJB
(from the collection you got from the find-method) the remainder of the record is
retrieved. (Eg. SELECT * FROM TABLE T WHERE PK=2; is carried out).
By setting <read-ahead>on-find</read-ahead> in combination with a eager-loading group
name, the find method returns besides the PK all fields defined in the group-name. (Eg
SELECT PK, FLD_A, FLD_B FROM TABLE T; is carried out when the find-method is invoked,
where FLD_A and FLD_B are elements of the "load group".)
Below a sample of jbosscmp-jdbc.xml with load-groups.
The read-ahead strategy can be set on bean level, but also on finder-method level. So,
if you've used a read-ahead strategy of on-find by default, the "none" read-ahead
strategy at finder-level will overwrite other read-ahead strategies.
I hope this will help. I hope you can give me some help in return:
I use JBoss3.2 and MySql4.0 and CMP. I have difficulties with reading BLOBs. Can you
tell me what mapping I need to use?
The mapping
<java-type>java.lang.Object</java-type>
<jdbc-type>BLOB</jdbc-type>
<sql-type>LONGBLOB</sql-type>
doesn't work for me. Or do I need to do something with a "serialized object".
Hope you can give me a piece of code.
Thank,
Evert Bende
http://www.wattabout.com
sample:
<jbosscmp-jdbc> <enterprise-beans> <ejb-name>GangsterEJB</ejb-name> <load-groups>
<load-group> <load-group-name>basic</load-group-name> <field-name>name</field-name>
<field-name>nickName</field-name> <field-name>badness</field-name></load-group>
<load-group> <load-group-name>contact info</load-group-name>
<field-name>nickName</field-name> <field-name>contactInfo</field-name>
<field-name>hangout</field-name> </load-group> </load-groups> </enterprise-beans>
</jbosscmp-jdbc>
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