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primary key on jboss

 
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Since EJB 2.0 does not support ejb-ql with MAX function, I was wondering how the primary keys are being created. The only way I could think of is to have a seperate table which could keep track of the next increment id for a table.
any suggestions.
- Walk rustin
 
Walk Rustin
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I am using jboss with mysql. Mysql supports auto generation of the primary key. Does JBoss supports this too? It will really take a lot of burden off the developer's shoulder.
- Walk rustin
 
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JBoss does support it. There's some element in the deployment descriptors that sets it. Check out the "entity-command" element in the DTD for the jbosscmp-jdbc deployment descriptors.
 
Walk Rustin
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thanks.
Jboss documentation is so poor that it's hard to find instructions on getting anything done. Same is the case with 'enity commands'. I paid $10.00 and bought the online documentation on CMP. It doesn't even mention 'entity commands'.
Does anyone have any working example of how to use 'entity commands'?
thanks.
- walker rustin
 
Nathaniel Stoddard
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Walker,
Have you used Google to search for "entity-command"? You may want to try that.
 
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What's the idea of using 'entity-command'. I suppose it is used so that the database doesn't have to generate the primary key for a record. By using this feature, the developer is asking jboss to generate a primary key and pass that key to the database. It means the primary key on the database should NOT be marked at auto-increment.
Is that assumption correct? Or Do I need to mark both at the jboss level and at the database level as auto-increment. Do they work in conjunction?
thanks.
- Walker
 
Walker Rustin
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IT WORKS!
Here is the complete code:
ejb-jar.xml
<entity>
<display-name>EmployeeEJB</display-name>
<ejb-name>EmployeeEJB</ejb-name>
<local-home>employee.ejb.com.sbm.cts.EmployeeHome</local-home>
<local>employee.ejb.com.sbm.cts.Employee</local>
<ejb-class>employee.ejb.com.sbm.cts.EmployeeBean</ejb-class>
<persistence-type>Container</persistence-type>
<prim-key-class>java.lang.Integer</prim-key-class>
<reentrant>False</reentrant>
<cmp-version>2.x</cmp-version>
<abstract-schema-name>EmployeeSchema</abstract-schema-name>
<cmp-field><field-name>firstname</field-name></cmp-field>
<cmp-field><field-name>lastname</field-name></cmp-field>
<cmp-field><field-name>telephone</field-name></cmp-field>
<cmp-field><field-name>employeeid</field-name></cmp-field>

<primkey-field>employeeid</primkey-field>
<resource-ref>
<res-ref-name>jdbc/ctsDB</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>
</entity>

jbosscmp-jdbc.xml
<entity>
<ejb-name>EmployeeEJB</ejb-name>
<table-name>employee</table-name>

<cmp-field>
<field-name>firstname</field-name>
<column-name>firstname</column-name>
</cmp-field>
<cmp-field>
<field-name>lastname</field-name>
<column-name>lastname</column-name>
</cmp-field>
<cmp-field>
<field-name>telephone</field-name>
<column-name>telephone</column-name>
</cmp-field>
<cmp-field>
<field-name>employeeid</field-name>
<column-name>employeeid</column-name>
<auto-increment/>
<not-null/>
</cmp-field>
<entity-command name="mysql-get-generated-keys"
class="org.jboss.ejb.plugins.cmp.jdbc.keygen.JDBCMySQLCreateCommand"/>
</entity>

code:
// HOME methods
public Integer ejbCreate(EmployeeDetails employeeDetails) throws CreateException {
logger.debug("ejbCreate");
try {
BeanUtils.copyProperties(this, employeeDetails);
} catch (java.lang.reflect.InvocationTargetException e) {
//nothing to log. It's expected because the primary key can't be
// changed.
logger.error("error in invocation" + e.getMessage());
} catch (Exception e) {
logger.error(e.getMessage());
}
return null;
}
public void ejbPostCreate(EmployeeDetails employeeDetails) {
logger.debug("ejbPostCreate");
}
// CMP field accessors
public abstract String getFirstname();
public abstract void setFirstname(String firstname);
public abstract String getLastname();
public abstract void setLastname(String lastname);
public abstract String getTelephone();
public abstract void setTelephone(String telephone);

public abstract Integer getEmployeeid();
public abstract void setEmployeeid(Integer employeeid);
sql code:
CREATE TABLE employee
(
firstname VARCHAR(30),
lastname VARCHAR(30),
telephone VARCHAR(30),
employeeid int(4) auto_increment,
CONSTRAINT pk_user PRIMARY KEY (employeeid)
);
Thanks everyone.
- walker
 
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Hi Walker,
did u generate you ejb with xdoclet?
if yes, could we please have that?
Thank you
Rudi
 
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I haven't convertend my code to xdoclete yet. I was just playing with the features of jboss. The xdoclet code is discussed in this forum of jboss.
http://jboss.org/index.html?module=bb&op=viewtopic&t=49321.
Hope it helps.
- Roger
 
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If/when you convert to use XDoclet, you might consider following the best practices and use the GUID Generator that it will generate for you.
 
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Hi All,
Now i have a problem in Multi- Threaded Environment. I have multiple threads running at the same time to collect the data from different source and store it the table using ejb create method. When i use Primary key generation through entity commands , i am getting duplicate keys generated. How to synchronize the way the keys are generated?

Thanks
Siva
 
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