Using Database Operations

DB2 Database Operations (JCD)

The same database operations are also used in the JCD, but appear as methods to call from the Collaboration.

Tables, Views, and Stored Procedures are manipulated through OTDs. Methods to call include:

insert()
insertRow()
update(String sWhere)
updateRow()
delete(String sWhere)
deleteRow()
select(String where)

Note –
Refer to the Javadoc for a full description of methods included in the [Please define the ProductName text entity].

The Table

A table OTD represents a database table. It consists of fields and methods. Fields correspond to the columns of a table while methods are the operations that you can apply to the OTD. This allows you to perform query, update, insert, and delete SQL operations in a table. The ability to update via a resultset is called “Updatable Resultset”, which is a feature supported by this adapter.

By default, the Table OTD has UpdatableConcurrency and ScrollTypeForwardOnly. Normally you do not have to change the default setting.

The type of result returned by the select() method can be specified using:

SetConcurrencytoUpdatable
SetConcurrencytoReadOnly
SetScrollTypetoForwardOnly
SetScrollTypetoScrollSensitive
SetScrollTypetoInsensitive

The Query (Select) Operation

To Perform a Query Operation on a Table

Execute the select() method with the “where” clause specified if necessary.

Note –
The content of the input.getText() file may contain null, meaning it will not have a “where” clause or it can contain a “where” clause such as empno > 50.

Loop through the ResultSet using the next() method.

Process the return record within a while() loop.

For example:

package prjDB2_JCDjcdALL;


public class jcdTableSelect
{

    public com.stc.codegen.logger.Logger logger;

    public com.stc.codegen.alerter.Alerter alerter;

    public com.stc.codegen.util.CollaborationContext collabContext;

    public com.stc.codegen.util.TypeConverter typeConverter;

    public void receive( com.stc.connector.appconn.file.FileTextMessage input,
 dtd.otdOutputDTD1325973702.
B_Employee otdOutputDTD_DB_Employee_1, otdDB2.OtdDB2OTD otdDB2_1,
com.stc.connector.appconn.
file.FileApplication FileClient_1 )
        throws Throwable
    {
        FileClient_1.setText( "Selectiong records from db_employee table via 
Table Select........" );
        FileClient_1.write();
        otdDB2_1.getDb_employee().select( input.getText() );
        while (otdDB2_1.getDb_employee().next()) {
            otdOutputDTD_DB_Employee_1.setEmpNo( typeConverter.shortToString
( otdDB2_1.getDb_employee().getEMP_NO(),
 "#", false, "" ) );
            otdOutputDTD_DB_Employee_1.setLastname( otdDB2_1.getDb_employee().
getLAST_NAME() );
            otdOutputDTD_DB_Employee_1.setFirstname( otdDB2_1.getDb_employee().
getFIRST_NAME() );
            otdOutputDTD_DB_Employee_1.setRate( otdDB2_1.getDb_employee().
getRATE().toString() );
            otdOutputDTD_DB_Employee_1.setLastDate( typeConverter.dateToString
( otdDB2_1.getDb_employee().
getLAST_UPDATE(), "yyyy-MM-dd hh:mm:ss", false, "" ) );
            FileClient_1.setText( otdOutputDTD_DB_Employee_1.marshalToString() );
            FileClient_1.write();
        }
        FileClient_1.setText( "Table Select Done." );
        FileClient_1.write();
    }

}

The Insert Operation

To Perform an Insert Operation on a Table

Execute the insert() method. Assign a field.

Insert the row by calling insertRow()

This example inserts an employee record.

package prjDB2_JCDjcdALL;


public class jcdInsert
{

    public com.stc.codegen.logger.Logger logger;

    public com.stc.codegen.alerter.Alerter alerter;

    public com.stc.codegen.util.CollaborationContext collabContext;

    public com.stc.codegen.util.TypeConverter typeConverter;

    public void receive( com.stc.connector.appconn.file.FileTextMessage 
input, otdDB2.OtdDB2OTD otdDB2_1,     dtd.otdInputDTD_1206505729.
DB_Employee otdInputDTD_DB_Employee_1, com.stc.connector.appconn.file.
FileApplication FileClient_1 )
        throws Throwable
    {
        FileClient_1.setText( "Inserting records in to db_employee table......" );
        FileClient_1.write();
        otdInputDTD_DB_Employee_1.unmarshalFromString( input.getText() );
        otdDB2_1.getDb_employee().insert();
        for (int i1 = 0; i1 < otdInputDTD_DB_Employee_1.countX_sequence_A(); i1 += 1) {
            otdDB2_1.getDb_employee().setEMP_NO( typeConverter.stringToShort
( otdInputDTD_DB_Employee_1.getX_sequence_A( i1 ).getEmpNo(), "#", false, 0 ) );
            otdDB2_1.getDb_employee().setLAST_NAME( otdInputDTD_DB_Employee_1.
getX_sequence_A( i1 ).getLastname() );
            otdDB2_1.getDb_employee().setFIRST_NAME( otdInputDTD_DB_Employee_1.
getX_sequence_A( i1 ).getFirstname() );
            otdDB2_1.getDb_employee().setRATE( new java.math.BigDecimal
( otdInputDTD_DB_Employee_1.getX_sequence_A( i1 ).getRate() ) );
            otdDB2_1.getDb_employee().setLAST_UPDATE( typeConverter.stringToTimestamp
( otdInputDTD_DB_Employee_1.getX_sequence_A( i1 ).getLastDate(), "yyyy-MM-dd hh:mm:ss",
 false, "" ) );
            otdDB2_1.getDb_employee().insertRow();
        }
        FileClient_1.setText( "Insert Done." );
        FileClient_1.write();
    }

}

The Update Operation

To Perform an Update Operation on a Table

Execute the update() method.

Note –
The content of the input.getText() file may contain null, meaning it will not have a “where” clause or it can contain a “where” clause such as empno > 50.

Using a while loop together with next(), move to the row that you want to update.

Assign updating value(s) to the fields of the table OTD

Update the row by calling updateRow().

package prjDB2_JCDjcdALL;


public class jcdUpdate
{

public com.stc.codegen.logger.Logger logger;
public com.stc.codegen.alerter.Alerter alerter;
public com.stc.codegen.util.CollaborationContext collabContext;
public com.stc.codegen.util.TypeConverter typeConverter;

    public void receive( com.stc.connector.appconn.file.FileTextMessage input, 
otdDB2.OtdDB2OTD otdDB2_1, com.stc.connector.appconn.file.FileApplication 
FileClient_1 )
        throws Throwable
    {
        FileClient_1.setText( "Updating the Rate and Last_update fields .. " );
        FileClient_1.write();
        otdDB2_1.getDb_employee().update( input.getText() );
        while (otdDB2_1.getDb_employee().next()) {
        otdDB2_1.getDb_employee().setLAST_NAME( "Krishna" );
        otdDB2_1.getDb_employee().setFIRST_NAME( "Kishore" );
        otdDB2_1.getDb_employee().updateRow();
        }
        FileClient_1.setText( "Update Done." );
        FileClient_1.write();
    }

}

The Delete Operation

To Perform a Delete Operation on a Table

Execute the delete() method.

Note –

The content of the input.getText() file may contain null, meaning it will not have a “where” clause or it can contain a “where” clause such as empno > 50.

In this example DELETE an employee.

package prjDB2_JCDjcdALL;

public class jcdDelete
{
public com.stc.codegen.logger.Logger logger;
public com.stc.codegen.alerter.Alerter alerter;
public com.stc.codegen.util.CollaborationContext collabContext;
public com.stc.codegen.util.TypeConverter typeConverter;

    public void receive( com.stc.connector.appconn.file.FileTextMessage input,
otdDB2.OtdDB2OTD otdDB2_1, com.stc.connector.appconn.file.FileApplication 
FileClient_1 )
        throws Throwable
    {
        FileClient_1.setText( "Deleting record............" );
        FileClient_1.write();
        otdDB2_1.getDb_employee().delete( input.getText() );
        FileClient_1.setText( "Delete Done." );
        FileClient_1.write();
    }
}

The Stored Procedure

A Stored Procedure OTD represents a database stored procedure. Fields correspond to the arguments of a stored procedure while methods are the operations that you can apply to the OTD. It allows you to execute a stored procedure. Remember that while in the Collaboration Editor you can drag and drop nodes from the OTD into the Collaboration Editor.

Executing Stored Procedures

The OTD represents the Stored Procedure “LookUpGlobal” with two parameters, an inbound parameter (INLOCALID) and an outbound parameter (OUTGLOBALPRODUCTID). These inbound and outbound parameters are generated by the DataBase Wizard and are represented in the resulting OTD as nodes. Within the Transformation Designer, you can drag values from the input parameters, execute the call, collect data, and drag the values to the output parameters.

Specify the input values.
Execute the Stored Procedure.
Retrieve the output parameters if any.

For example:

package Storedprocedure;

public class sp_jce
{

    public com.stc.codegen.logger.Logger logger;

    public com.stc.codegen.alerter.Alerter alerter;

    public void receive( com.stc.connector.appconn.file.FileTextMessage input,
com.stc.connector.appconn.file.FileApplication FileClient_1,employeedb.
Db_employee employeedb_with_top_db_employee_1,insert_DB.Insert_DBOTD insert_DB_1 )
    throws Throwable
    {

        employeedb_with_top_db_employee_1.unmarshalFromString( input.getText() );

        insert_DB_1.getInsert_new_employee().setEmployee_no( java.lang.Integer.
parseInt( employeedb_with_top_db_employee_1.getEmployee_no() ) );

        insert_DB_1.getInsert_new_employee().setEmployee_Lname
( employeedb_with_top_db_employee_1.getEmployee_lname() );

        insert_DB_1.getInsert_new_employee().setEmployee_Fname
( employeedb_with_top_db_employee_1.getEmployee_fname() );

        insert_DB_1.getInsert_new_employee().setRate( java.lang.Float.parseFloat
( employeedb_with_top_db_employee_1.getRate() ) );

        insert_DB_1.getInsert_new_employee().setUpdate_date( java.sql.Timestamp.valueOf
( employeedb_with_top_db_employee_1.getUpdate_date() ) );

        insert_DB_1.getInsert_new_employee().execute();

        insert_DB_1.commit();

        FileClient_1.setText( "procedure executed" );

        FileClient_1.write();
    }

}

Manipulating the ResultSet and Update Count Returned by Stored Procedure

For Stored Procedures that return ResultSets and Update Count, the following methods are provided to manipulate the ResultSet:

enableResultSetOnly
enableUpdateCountsOnly
enableResultSetandUpdateCounts
resultsAvailable
next
getUpdateCount
available

DB2 stored procedures do not return records as ResultSets, instead, the records are returned through output reference cursor parameters. Reference Cursor parameters are essentially ResultSets.

The resultsAvailable() method, added to the PreparedStatementAgent class, simplifies the whole process of determining whether any results, be it Update Counts or ResultSets, are available after a stored procedure has been executed. Although JDBC provides three methods (getMoreResults(), getUpdateCount(), and getResultSet()) to access the results of a stored procedure call, the information returned from these methods can be quite confusing to the inexperienced Java JDBC programmer and they also differ between vendors. You can simply call resultsAvailable() and if Boolean true is returned, you can expect either a valid Update Count when getUpdateCount() is called and/or the next ResultSet has been retrieved and made available to one of the ResultSet nodes defined for the Stored Procedure OTD, when that node’s available() method returns true.

Frequently, Update Counts information that is returned from a Stored Procedures is insignificant. You should process returned ResultSet information and avoid looping through all of the Update Counts. The following three methods control exactly what information should be returned from a stored procedure call. The enableResultSetsOnly() method, added to the PreparedStatement Agent class allows only ResultSets to be returned and thus every resultsAvailable() called only returns Boolean true if a ResultSet is available. Likewise, the enableUpdateCountsOnly() causes resultsAvailable() to return true only if an Update Count is available. The default case of enableResultsetsAndUpdateCount() method allows both ResultSets and Update Counts to be returned.

Collaboration usability for a stored procedure ResultSet

The Column data of the ResultSets can be dragged-and-dropped from their nodes to the Business Rules. Below is a code snippet that can be generated by the Collaboration Editor:

while (getSPIn().getSpS_multi().resultsAvailable())
{
if (getSPIn().getSpS_multi().getUpdateCount() > 0)
  {
    System.err.println("Updated "+getSPIn().getSpS_multi()
.getUpdateCount()+" rows");
  }

  if (getSPIn().getSpS_multi().getNormRS().available())
  {
    while (getSPIn().getSpS_multi().getNormRS().next())
    {
      System.err.println("Customer Id   = "+getSPIn().getSpS_multi().
getNormRS().getCustomerId());
      System.err.println("Customer Name = "+getSPIn().getSpS_multi()
getNormRS().getCustomerName());
      System.err.println();
    }
    System.err.println("===");
  }
  else if (getSPIn().getSpS_multi().getDbEmployee().available())
  {
    while (getSPIn().getSpS_multi().getDbEmployee().next())
    {
      System.err.println("EMPNO    = "+getSPIn().getSpS_multi().
getDbEmployee().getEMPNO());
      System.err.println("ENAME    = "+getSPIn().getSpS_multi().
getDbEmployee().getENAME());
      System.err.println("JOB      = "+getSPIn().getSpS_multi().
getDbEmployee().getJOB());
      System.err.println("MGR      = "+getSPIn().getSpS_multi().
getDbEmployee().getMGR());
      System.err.println("HIREDATE = "+getSPIn().getSpS_multi().
getDbEmployee().getHIREDATE());
      System.err.println("SAL      = "+getSPIn().getSpS_multi().
getDbEmployee().getSAL());
      System.err.println("COMM     = "+getSPIn().getSpS_multi().
getDbEmployee().getCOMM());
      System.err.println("DEPTNO   = "+getSPIn().getSpS_multi().
getDbEmployee().getDEPTNO());
      System.err.println();
    }
    System.err.println("===");
  }
}

Note –

resultsAvailable() and available() cannot be indiscriminately called because each time they move ResultSet pointers to the appropriate locations.

After calling "resultsAvailable()", the next result (if available) can be either a ResultSet or an UpdateCount if the default "enableResultSetsAndUpdateCount()" was used.

Because of limitations imposed by some DBMSs, it is recommended that for maximum portability, all of the results in a ResultSet object should be retrieved before OUT parameters are retrieved. Therefore, you should retrieve all ResultSet(s) and Update Counts first followed by retrieving the OUT type parameters and return values.

The following list includes specific ResultSet behavior that you may encounter:

The method resultsAvailable() implicitly calls getMoreResults() when it is called more than once. You should not call both methods in your java code. Doing so may result in skipped data from one of the ResultSets when more than one ResultSet is present.
The methods available() and getResultSet() can not be used in conjunction with multiple ResultSets being open at the same time. Attempting to open more the one ResultSet at the same time closes the previous ResultSet. The recommended working pattern is:
- Open one Result Set (ResultSet_1) and work with the data until you have completed your modifications and updates. Open ResultSet_2, (ResultSet_1 is now closed) and modify. When you have completed your work in ResultSet_2, open any additional ResultSets or close ResultSet_2.
If you modify the ResultSet generated by the Execute mode of the Database Wizard, you need to assure the indexes match the stored procedure. By doing this, your ResultSet indexes are preserved.
Generally, getMoreResults does not need to be called. It is needed if you do not want to use our enhanced methods and you want to follow the traditional JDBC calls on your own.

The DBWizard Assistant expects the column names to be in English when creating a ResultSet.

Prepared Statement

A Prepared Statement OTD represents a SQL statement that has been compiled. Fields in the OTD correspond to the input values that users need to provide.

Prepared statements can be used to perform insert, update, delete and query operations. A prepared statement uses a question mark (?) as a place holder for input. For example:

insert into EMP_TAB(Age, Name, Dept No) value(?, ?, ?)

To execute a prepared statement, set the input parameters and call executeUpdate() and specify the input values if any.

getPrepStatement().getPreparedStatementTest().setAge(23);
getPrepStatement().getPreparedStatementTest().setName(”Peter Pan’);
getPrepStatement().getPreparedStatementTest().setDeptNo(6);
getPrepStatement().getPreparedStatementTest().executeUpdate();

Batch Operations

To achieve better performance, consider using a bulk insert if you have to insert many records. This is the “Add Batch” capability. The only modification required is to include the addBatch() method for each SQL operation and then the executeBatch() call to submit the batch to the database server. Batch operations apply only to Prepared Statements.

getPrepStatement().getPreparedStatementTest().setAge(23);
getPrepStatement().getPreparedStatementTest().setName(”Peter Pan’);
getPrepStatement().getPreparedStatementTest().setDeptNo(6);
getPrepStatement().getPreparedStatementTest().addBatch();

getPrepStatement().getPreparedStatementTest().setAge(45);
getPrepStatement().getPreparedStatementTest().setName(”Harrison Ford’);
getPrepStatement().getPreparedStatementTest().setDeptNo(7);
getPrepStatement().getPreparedStatementTest().addBatch();
getPrepStatement().getPreparedStatementTest().executeBatch();