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 follows:

MySumFld.java

//Template
package myudo;

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

/**
 * This class extends from 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 setenv.bat in <install_root>\bin by appending the path of the four classes to the batch file's ADDCLASSPATH variable. Assume that the four classes are located in D:\test\myudo.
set ADDCLASSPATH=%JAVAHOME%\lib\tools.jar;D:\test;
Start JReport Designer.
Click Insert > UDO. You will now find a new UDO object named MySumFld in the drop-down list of the Insert UDO dialog.