Version 8.3.2
 —  Special Development Topics  —

DBCOMBO

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

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.

graphics/image237.png

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.

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Properties

Basic
valueprop

Property that returns a DBCOMBOInfo -instance. This instance provides for the combo box options that are read from database as well as for a convenient way to append the filter value to query string.

Obligatory  
querycolumn

Name of the column in the query to that the filter criteria is belongs to. This column may differ from the value help table/column (properties VALUEHELPTABLE, VALUEHELPCOLUMN). This name is used to build a SQL string in method "toSQLString".

Obligatory  
datasource

Logical identifier of the data source to use. This name is passed to the connection provider in method "IDBQUERYConnectionProvider.getDBConnection".

Obligatory  
valuehelptable

Name of the table from there the list of valid values can be read.

Obligatory  
valuehelpcolumn

Name of the column from there the list of valid values can be read.

Obligatory  
valuehelpcolumndescr

Name of a column where an additional description of the valid values is stored. The name must identify a column inside the "value help table" (property VALUEHELPTABLE).

Optional  
size

Integer value that defines the number of lines being displayed. If the SIZE is set to "1", the selection is displayed as combo box. If it is set to ">1", it is displayed as multi line selection.

Optional  
flush

Flushing behaviour\; please view "Common Rules" for details

Optional

screen

server

displayonly

If set to "true", the DBCOMBO will not be accessible for input. It is just used as an output field.

Optional  
width

Width of DBCOMBO in pixels or as percentage value.

Optional

100

120

140

160

180

200

50%

100%

align

Explicit Alignment

Optional

left

center

right

valign

Explicit Alignment

Optional

top

middle

bottom

colspan

Number of columns occupied by this control.

Optional

1

2

3

4

5

50

int-value

rowspan

Number of rows occupied by this control.

Optional

1

2

3

4

5

50

int-value

combostyle

Explicit style information passed to the DBCOMBO.

Example: if you want the text inside the DBCOMBO to be right aligned, define "text-align: right".

Optional  
helpid

Identifier that is used for building the URL of the online help page. Please refer to "Online Help Management" for details.

Optional  
comment

Comment without any effect on rendering and behaviour. The comment is shown in the layout editor's tree view.

Optional  

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