iReport Ultimate Guide - Nimsoft Library

Data Sources and Query Executersof the directory name to list. The aim of the operation, in fact, is to return a list of file names encapsulated in a bean array datasource.Our CustomQueryExecuter will look like the following:Code Example 11-12 The source of our QueryExecuter implementationpackage samples.queryexecuter;import java.io.File;import net.sf.jasperreports.engine.JRDataSource;import net.sf.jasperreports.engine.JRException;import net.sf.jasperreports.engine.data.JRBeanArrayDataSource;import net.sf.jasperreports.engine.query.JRQueryExecuter;public class CustomQueryExecuter implements JRQueryExecuter {File directory = null;public CustomQueryExecuter(File directory){this.directory = directory;}public JRDataSource createDatasource() throws JRException {// Creates a list of files and present them using the CustomDataSourceif (directory != null && directory.exists() && directory.isDirectory()){File[] files = directory.listFiles();return new CustomDataSource(files);}throw new JRException("Invalid directory!");}public void close() {// Nothing to do in this implementation}}public boolean cancelQuery() throws JRException {// Too fast to be interrupted... :-)return false;}Up to now we have created the CustomQueryExecuterFactory and the CustomQueryExecuter, which uses a class calledCustomDataSource. This class extends the JRBeanArrayDataSource. In this sample, we may just use aJRBeanArrayDataSource, but the implementation of another custom data source can be useful to introduce the next task:creating and using a FieldsProvider.215