Custom datasources

So far we've seen all of the JRDataSource implementations provided by JasperReports. If we need to extract data from a type of datasource not directly supported by JasperReports, we can create a class implementing JRDataSource to meet our needs. In this section, we will create a custom datasource allowing us to generate reports from an instance of java.util.List containing arrays of strings as its elements.

Writing a custom JRDataSource implementation

In our previous examples, all JasperReports datasources implement the JRDataSource interface. JasperReports also includes the net.sf.jasperreports.engine.JRRewindableDataSource interface. This interface extends JRDatasource, adding a single method called moveFirst(). The moveFirst() method is intended to move the cursor to the first element in the datasource. Our custom datasource will implement JRRewindableDataSource. Let's take a look at the source of the custom datasource class.

package net.ensode.jasperbook;

import java...