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The DBCOMBO control represents a filter criterion of a database query. It provides for a value help that is read from the database and a convenient way to append the filter criterion to the SELECT statement. In contrast to DBFIELD, the valid values are read from the database when the page is loaded.

This document covers the following topics:

• Example

• Properties

Example

The following image shows an example in which a DBCOMBO control is used for the filter criterion "Country" within a simple business partner report. The combo box options are read from table "COUNTRY" when the page is loaded.

Have a look at the XML layout definition:

<rowarea name="Filter Criteria">
    <itr>
        <label name="Country" width="80">
        </label>
        <dbcombo valueprop="dBComboCountry" querycolumn="COUNTRY" datasource="addressdb"
                 valuehelptable="COUNTRY" valuehelpcolumn="ID" width="80">
        </dbcombo>
        <hdist width="100%">
        </hdist>
        <button name="Execute" method="onExecute">
        </button>
    </itr>
</rowarea>
<vdist>
</vdist>
<rowarea name="Result" height="140">
    <itr height="100%">
        <textgridsss2 griddataprop="result" rowcount="5" width="100%">
            <column name="Title" property="TITLE" width="50">
            </column>
            <column name="Last Name" property="LASTNAME" width="100">
            </column>
            <column name="First Name" property="FIRSTNAME" width="100">
            </column>
            <column name="Country" property="COUNTRY" width="50">
            </column>
            <column name="State" property="STATE" width="100%">
            </column>
        </textgridsss2>
    </itr>
</rowarea>

The corresponding adapter code is:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;

import com.softwareag.cis.server.Adapter;
import com.softwareag.cis.server.util.DBCOMBOInfo;
import com.softwareag.cis.server.util.DBTEXTGRIDCollection;
import com.softwareag.cis.server.util.DBUtil;
import com.softwareag.cis.server.util.DelegateError;
import com.softwareag.cis.server.util.IDBCondition;
import com.softwareag.cis.server.util.IDBQUERYConnectionProvider;



// This class is a generated one.


public class DBCOMBO_Adapter
    extends Adapter
    implements IDBQUERYConnectionProvider, IDBDemoAdapter
{
    // ------------------------------------------------------------------------
    // members
    // ------------------------------------------------------------------------

    private int m_port = 9001;
    private int m_dbPort = 9001;
    private Connection m_connection;
...
    DBQUERYStartDatabaseThread m_startDemoDBThread;
    // ------------------------------------------------------------------------
    // property access
    // ------------------------------------------------------------------------

    // property >port<
    public void setPort(int value) { m_port = value;}
    public int getPort(){ return m_port;}

    // property >dbComboCountry<
    DBCOMBOInfo m_dBComboCountry = new DBCOMBOInfo(this);
    public DBCOMBOInfo getDBComboCountry() { return m_dBComboCountry; }

    // property >result<
    DBTEXTGRIDCollection m_result = new DBTEXTGRIDCollection();
    public DBTEXTGRIDCollection getResult() { return m_result; }
    public void setResult(DBTEXTGRIDCollection value) { m_result = value; }
...
    // ------------------------------------------------------------------------
    // public adapter methods
    // ------------------------------------------------------------------------

    public Connection getDBConnection(String datasource)
    {
        try
        {
            if (m_connection == null)
            {
                String jdbcDriverClassName = "org.hsqldb.jdbcDriver";
                String jdbcUrl = "jdbc:hsqldb:hsql://localhost:"+m_dbPort;
                String user = "sa";
                String password = "";
                Class.forName(jdbcDriverClassName);
                m_connection = DriverManager.getConnection(jdbcUrl, user, password);
            }
            return m_connection;
        }
        catch (Exception exc)
        {
            throw new DelegateError(exc);
        }
    }
...
    public void onExecute()
    {
        try
        {
            StringBuffer sb = new StringBuffer();
            sb.append("SELECT * FROM BUSINESSPARTNER INNER JOIN ADDRESS ON BUSINESSPARTNER.ID =
                                ADDRESS.BUSINESSPARTNERID");
            DBUtil.addToQuery(sb, new IDBCondition[] { m_dBComboCountry }, true);
            String dataSource = m_dBComboCountry.getDataSource();
            Connection con = getDBConnection(dataSource);
            ResultSet rs = con.createStatement().executeQuery(sb.toString());
            m_result.initWithResultSet(rs);
        }
        catch (Exception exc)
        {
            throw new DelegateError(exc);
        }
    }
}

The property dBComboCountry is of type DBCOMBOInfo (from the package com.softwareag.cis.server.util). The DBCOMBOInfo implements (like all DB controls) the interface IDBCondition (com.softwareag.cis.server.util). With class DBUtil (com.softwareag.cis.server.util), you can append values of the filter criteria to the SELECT statement in a convenient way. See the JavaDoc documentation of class DBUtil for details.

The DBCOMBOInfo class does not open a database connection on its own (same to all DB controls). The embedding adapter provides for an implementation of interface IDBQUERYConnectionProvider (com.softwareag.cis.server.util) when creating a DBCOMBOInfo object. The interface method getDBConnection is called once - at the first time the DBCOMBOInfo has to access the database. There are no updates (insert/update/delete) done with this connection. As the DBCOMBOInfo does not open the connection, it does not care about closing the connection.

For displaying the result, the class DBTEXTGRIDCollection (from the package com.softwareag.cis.server.util) is used. This class extends TEXTGRIDCollection by the ability to initialise the collection with a result set (java.sql.ResultSet). For each line of the result set, it creates an object of class DBTEXTGRIDLine (package com.softwareag.cis.server.util). Class DBTEXTGRIDLine implements the interface IDynamicAccess. With this, "normal" text grid controls can be used to visualize the data of the DBTEXTGRIDCollection.

Properties

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