1.2.4. Class-Defined Template

Class-defined templates are used when it is too difficult or impossible to select data using SQL, JPQL or Groovy. They are used, for example, when the report is a result of combining several other reports.

The class defining the template must implement the com.haulmont.yarg.formatters.CustomReport interface. In the class, you need to define the createReport() method, which returns an array of bytes and takes the following input parameters:

  • report - report descriptor of the com.haulmont.yarg.structure.Report type.

  • rootBand - root band data of the com.haulmont.yarg.structure.BandData type.

  • params - map of external report parameters.

Below is an example of a simple class-defined template. It creates an HTML document showing the name of a book selected as report parameter:

package com.sample.library.report;

import com.haulmont.yarg.formatters.CustomReport;
import com.haulmont.yarg.structure.BandData;
import com.haulmont.yarg.structure.Report;
import com.sample.library.entity.Book;
import java.util.Map;

public class BookReport implements CustomReport {
    public byte[] createReport(Report report, BandData rootBand, Map<String, Object> params) {
        Book book = (Book) params.get("book");
        String html = "<html><body>";
        html += "<p>Name: " + book.getName() + "</p>";
        html += "</body></html>";
        return html.getBytes();