Develop a custom DataStoreHelper class

Develop a custom DataStoreHelper class

Apply the WebSphere extension, GenericDataStoreHelper class, to create our own data store helper for data sources that the application server does not support. With this helper class, your JDBC configuration can use database-specific functions during transactions.

If we are using a configuration with a data source that is not supported by the application server, we might want to create a custom data store helper. This helper will allow us to leverage the database to perform functions during a transaction that would not otherwise be available. You will need to create a user-defined DataStoreHelper class, and there is information for creating a new exception handler to catch any exceptions that might be created with the use of our custom data handler.

Deprecated feature: The CUSTOM_HELPER constant field in the com.ibm.websphere.rsadapter.DataStoreHelper class API is deprecated. If we create our own DataStoreHelper implementation class, do not invoke setHelperType(DataStoreHelper.CUSTOM_HELPER). Instead, let the HelperType value be set by the implementation class from which it inherits.depfeat

Tasks
Create a class that extends the existing data store helpers. Use the following code as an example; this type of data source is based on a user-defined JDBC provider:
package com.ibm.websphere.examples.adapter;

import java.sql.SQLException;
import javax.resource.ResourceException;

import com.ibm.websphere.appprofile.accessintent.AccessIntent;
import com.ibm.websphere.ce.cm.*;
import com.ibm.websphere.rsadapter.WSInteractionSpec;

/**
* Example DataStoreHelper class, demonstrating how to create a user-defined DataStoreHelper.
* The implementation for each method is provided only as an example.  More detail is probably
* required for any custom DataStoreHelper created for use by a real application.
* In this example, we will override the doStatementCleanup(),getIsolationLevel(), and set userDefined 
* exception map.
*/
public class ExampleDataStoreHelper extends com.ibm.websphere.rsadapter.GenericDataStoreHelper
{

    public ExampleDataStoreHelper(java.util.Properties props)
    {
        super(props);

        // Update the DataStoreHelperMetaData values for this helper.
        getMetaData().setGetTypeMapSupport(false);

        // Update the exception mappings for this helper.
        java.util.Map xMap = new java.util.HashMap();

        // Add an Error Code mapping to StaleConnectionException.
        xMap.put(new Integer(2310),  StaleConnectionException.class);
        // Add an Error Code mapping to DuplicateKeyException.
        xMap.put(new Integer(1062),  DuplicateKeyException.class);
        // Add a SQL State mapping to the user-defined ColumnNotFoundException
        xMap.put("S0022",            ColumnNotFoundException.class);
        // Undo an inherited StaleConnection SQL State mapping.
        xMap.put("S1000",            Void.class);

        setUserDefinedMap(xMap);

        // If we are extending a helper class, it is
        // normally not necessary to issue 'getMetaData().setHelperType(...)'
        // because our custom helper will inherit the helper type from its
        // 	parent class.
                          

         }

    public void doStatementCleanup(java.sql.PreparedStatement stmt) throws SQLException
    {
        // Clean up the statement so it may be cached and reused.

        stmt.setCursorName("");
        stmt.setEscapeProcessing(true);
        stmt.setFetchDirection(java.sql.ResultSet.FETCH_FORWARD);
        stmt.setMaxFieldSize(0);
        stmt.setMaxRows(0);
        stmt.setQueryTimeout(0);
    }



    public int getIsolationLevel(AccessIntent intent) throws ResourceException
    {
        // Determine an isolation level based on the AccessIntent.

        // set WebSphere default isolation level to TRANSACTION_SERIALIZABLE.
        if (intent == null) return java.sql.Connection.TRANSACTION_SERIALIZABLE;

        return intent.getConcurrencyControl() == AccessIntent.CONCURRENCY_CONTROL_OPTIMISTIC ?
               java.sql.Connection.TRANSACTION_READ_COMMITTED :
               java.sql.Connection.TRANSACTION_REPEATABLE_READ;
    }
        public int getLockType(AccessIntent intent) {
           if ( intent.getConcurrencyControl() == AccessIntent.CONCURRENCY_CONTROL_PESSIMISTIC) {
              if ( intent.getAccessType() == AccessIntent.ACCESS_TYPE_READ ) {
                  return WSInteractionSpec.LOCKTYPE_SELECT;
              }
              else {
                  return WSInteractionSpec.LOCKTYPE_SELECT_FOR_UPDATE;
               }
           }
           return WSInteractionSpec.LOCKTYPE_SELECT;
        }
}
Optional: Create our own exception handler class. Use the following code as a guide:
package com.ibm.websphere.examples.adapter;

import java.sql.SQLException;
import com.ibm.websphere.ce.cm.PortableSQLException;

/**
* Example PortableSQLException subclass, which demonstrates how to create a user-defined
* exception for exception mapping.
*/
public class ColumnNotFoundException extends PortableSQLException
{
    public ColumnNotFoundException(SQLException sqlX)
    {
        super(sqlX);
    }
}
Compile the newly created DataStoreHelper class or classes. You will need the following JAR files in the classpath to compile them:

app_server_root/dev/JavaEE/j2ee.jar
app_server_root/dev/was_public.jar
was_public.jar contains classes from app_server_root/lib/rsahelpers.jar needed to compile a custom DataStoreHelper class.
app_server_root/plugins/com.ibm.ws.runtime.jar
If we are using a development environment, such as Eclipse, we need to set these JAR files in the classpath to be able to compile. Then, create a JAR file of the project after we have finished editing the files (see the help documentation for our development environment for specific instructions).
If we do not have development environment, and we are using the javac compiler:
Create your .java file that extends the GenericDataStoreHelper or any other data store helper, as shown in Step 1.
Change to your home directory after we are done editing your file or files in the command line utility.
Set the classpath using this command:
(Windows)
set CLASSPATH=%CLASSPATH%;app_server_root\dev\JavaEE\j2ee.jar;app_server_root\dev\was_public.jar;app_server_root\plugins\com.ibm.ws.runtime.jar
(UNIX)
 set CLASSPATH=$CLASSPATH:app_server_root/dev/JavaEE/j2ee.jar:app_server_root/dev/was_public.jar:app_server_root/plugins/com.ibm.ws.runtime.jar
Compile your class or classes. For example, on Windows operating systems enter (this will compile all the .java files in the directory specified):
C:\javac your_directory\*.java
From the Java directory, create a JAR file of all the compiled class files in your directory. For example, enter the following command on Windows operating systems (change myFile to the name we want for your JAR file):
 C:\Java> jar cf myFile.jar *.class
For more information on using the javac compiler go to the Oracle website for the Java compiler.
Place your compiled JAR files in a directory, and update the class path for the JDBC provider to include that location. For example, if your JAR file is c:\myFile.jar, then make sure to modify the JDBC class path to include c:\myFile.jar.
Click Resources > JDBC > JDBC Providers > JDBC_provider.
In the Class path field, add the location of the JAR files that you compiled. For example, press ENTER in the field and add a new line:
c:\myFile.jar
Configure the application server to use the new custom DataStoreHelper class.

From the administrative console select Resources > JDBC > Data Sources.
Select the data source to configure with our custom DataStoreHelper class.
In the section labeled Data store helper class name, select Specify a user-defined data store helper.
Enter the class name for the data store helper that we created.
Apply our changes and select OK.
Related:

Relational resource adapters and JCA