Example 2: Making a group based on a UDO

This example describes how to make a group based on a UDO. This sample is similar to a summary field. This example includes the implementation of four classes and shares a class with Example 1.

Create the template, result, creator and render files as below:

MySumFld.java

//Template
package myudo;

import jet.report.*;
import jet.controls.*;

/**
 * This class extends form JRObjectTemplate, add two properties "ColumnName" and
 * "TextColor".
 */
public class MySumFld extends MyDbFld {
        public MySumFld() {
                super();
        }

        /**
         * Return the instance name prefix.
         */
        public String getPrefix() {
                return "MySumField";
        }

        public boolean isGroupListener() {
                return true;
        }
}

MySumFldRst.java

//Result
package myudo;

import jet.JRStopEngineException;
import jet.connect.Record;
import jet.connect.DbValue;
import jet.util.*;
import jet.datastream.*;
import java.io.*;

public class MySumFldRst extends MyDbFldRst {
        double value;

        public MySumFldRst() {
        }

        // make the text will be displayed. 
        String getText() {
                return "" + value;
        }

        /**  
         * Read the data from DataInput. 
         * UDO can override this method to restore its own data. 
         * @throws JRStopEngineException 
         * */
        protected void readProperties(DataInput in, DSDataStreamable ds)
                        throws IOException, JRStopEngineException {
                super.readProperties(in, ds);
                value = in.readDouble();
        }

        /**  
         * Write the data to DataInput. 
         * UDO can override this method to save its own data. 
         * */
        protected void writeProperties(DataOutput out) throws IOException {
                super.writeProperties(out);
                out.writeDouble(value);
        }
}

MySumFldCreator.java

//Creator
package myudo;

import java.awt.*;
import java.util.*;
import jet.report.*;
import jet.controls.*;
import jet.connect.*;
import jet.udo.*;
import jet.datastream.*;
import guitools.Painter;
import jet.util.*;

/**
 * * Implements JRObjectResultCreator for creating JRObjectResult in JReport *
 * Engine Bean.
 */
public class MySumFldCreator implements JRObjectResultCreator, JRGroupListener { 
        // This interface must implement by JRObjectCreator.
        MySumFld rpt;

        MySumFldRst dsField;

        double value;

        public MySumFldCreator() {
        }

        public void setTemplate(JRObjectTemplate rptobj) {
                rpt = (MySumFld) rptobj;
        }

        public JRObjectResult createJRObjectResult(JRObjectTemplate rptobj,
                        Record record) {
                rpt = (MySumFld) rptobj;
                MySumFldRst dsField = new MySumFldRst();
                dsField.setTemplate(rpt);
                dsField.value = value;
                return dsField;
        }

        /** * This method will be called before the first record. */
        public void prepareFetchRecords() {
                value = 0.0;
        }

        /** * This method will be called after the last record. */
        public void finishFetchRecords() {
        }

        /** * This method will be called each record. */
        public void fetchNewRecord(Record record) {
                String colName = (String) rpt.getPropertyByName("ColumnName")
                                .getObject();
                // return the column value.
                DbNumber num = (DbNumber) record.getCell(colName);
                if (!num.isNull()) {
                        value += num.intValue();
                }
        }
}

MyDbFldRender.java (See Example 1 for details.)

Compile the four Java files in the same way as Example 1.

Modify udo.ini in <install_root>\lib\ by appending the four classes as follows:

Begin
name=MySumFld 
template=myudo.MySumFld 
resultobject=myudo.MySumFldRst 
resultcreator=myudo.MySumFldCreator 
resultviewer=myudo.MyDbFldRender
End

Edit JReport.bat in <install_root>\bin by appending the four classes to the class path. Assume that the four classes are located in d:\test\myudo.
Change: ... -classpath "c:\jreport\designer\lib\report.jar; ...c:\temp" ...
To : ... -classpath "c:\jreport\designer\lib\report.jar;d:\test; ... c:\temp" ...
Start JReport Designer with the modified batch file.
Click Insert > UDO. You will now find a new UDO object named MySumFld in the drop-down list of the Insert UDO dialog.