package myPackage;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.util.HashMap;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import net.sf.jasperreports.engine.JRResultSetDataSource;
import net.sf.jasperreports.engine.JasperFillManager;
import net.sf.jasperreports.engine.JasperPrint;
import net.sf.jasperreports.view.JasperViewer;

public class MyReport {

	private Connection getConnection() {
		try {
			Class.forName("org.postgresql.Driver");
			return DriverManager.getConnection("jdbc:postgresql://localhost:5432/my_db", "postgres", "123456789");
		} catch (Exception ex) {
			ex.printStackTrace();
			return null;
		}
	}

	private StringBuffer getSQL() {
		StringBuffer sql = new StringBuffer();
		sql.append("select *");
		sql.append(" from sample_table");
		//
		return sql;
	}

	public void showReport() {
		try {
				String reportName = "path/to/my_report.jasper";
				//
				StringBuffer sql;
				sql = getSQL();
				String wsql = " where";

				// a filter
				if (myCombo.getSelectedIndex() > -1) {
					sql.append(wsql).append(" some_field = '").append(myCombo.getSelectedItem().toString()).append("'");
					wsql = " and";
				}

				// another filter
				if (myTextField.getText().trim().length() > 0) {
					sql.append(wsql).append(" some_other_field = '").append(myTextField.getText()).append("'");
				}

				// SQL ending
				sql.append(" order by another_field");

				Connection connection = getConnection();
				Statement stmt = connection.createStatement();
				Hashmap parameters = new HashMap(); //set the report parameters here
				JRResultSetDataSource jrrs = new JRResultSetDataSource(stmt.executeQuery(sql.toString()));
				InputStream is = this.getClass().getClassLoader().getResourceAsStream(reportName);
				JasperPrint jasperPrint = JasperFillManager.fillReport(is, parameters, jrrs);
				if (jasperPrint.getPages().size() > 0) {
					JasperViewer jv = new JasperViewer(jasperPrint, false);
					jv.setTitle("My Report");
					jv.setExtendedState(JFrame.MAXIMIZED_BOTH);
					jv.setModalExclusionType(ModalExclusionType.APPLICATION_EXCLUDE);
					jv.setVisible(true);
				} else {
					JOptionPane.showMessageDialog(this, "Some message to show when the SQL returns nothing.");
				}

			} catch (Exception ex) {
				ex.printStackTrace();
			}
	}
}