Working With Design Patterns: Abstract Factory
Listing 6: HtmlCatalogReportFactory.
import domain.*;
public class HtmlCatalogReportFactory extends CatalogReportFactory {
public HtmlCatalogReportFactory(Catalog catalog) {
super(catalog);
}
@Override
protected ReportComponent createDetailRecord(Material material) {
return new HtmlReportDetailRecord(material);
}
@Override
protected ReportComponent createReportHeader() {
return new HtmlReportHeader();
}
@Override
protected ReportComponent createSummary() {
return new HtmlReportSummary();
}
}
Listing 7: MaterialSorter.
import java.util.*;
import domain.*;
public class MaterialSorter implements Comparator<Material> {
private List<Material> materialsCopy;
public MaterialSorter(List<Material> materials) {
materialsCopy = new ArrayList<Material>(materials);
}
@Override
public int compare(Material material1, Material material2) {
if (material1.getClass() == material2.getClass()) {
if (material1.getTitle().equals(material2.getTitle()))
return material1.getAuthor().
compareTo(material2.getAuthor());
return material1.getTitle().
compareTo(material2.getTitle());
}
return material1.getClass().getName().
compareTo(material2.getClass().getName());
}
public List<Material> sort() {
Collections.sort(materialsCopy, this);
return materialsCopy;
}
}
Each creation method returns a ReportComponent:
public interface ReportComponent {
void appendTo(Report report);
}
The job of a ReportComponent is to produce some amount of text that can be appended to a Report. A Report is a simple helper class—basically a wrapper for StringBuilder—that adds a few useful elements to help simplify client code:
public class Report {
static final String EOL = System.getProperty("line.separator");
private StringBuilder buffer = new StringBuilder();
@Override
public String toString() {
return buffer.toString();
}
public void appendLine(String text) {
buffer.append(text);
buffer.append(EOL);
}
}
Each of the HTML report component factories is, for the most part, a trivial one-line method. The three implementations, plus the Html utility class, appear in Listing 8.
Listing 8: HTML factory components.
// Html.java
public class Html {
public static String td(String element) {
return tag(element, "td");
}
public static String th(String element) {
return tag(element, "th");
}
public static String tag(String element, String tag) {
return String.format("<%s>%s</%s>", tag, element, tag);
}
}
// HtmlReportHeader.java
import static abstractfactory.Html.*;
public class HtmlReportHeader implements ReportComponent {
@Override
public void appendTo(Report report) {
report.appendLine("<body>");
report.appendLine("<table>");
report.appendLine(String.format("<tr>%s%s%s%s</tr>",
th("Title"), th("Auth/Dir"),
th("Classification"), th("Year")));
}
}
// HtmlReportDetailRecord.java
import static abstractfactory.Html.*;
import domain.*;
public class HtmlReportDetailRecord implements ReportComponent {
private final Material material;
public HtmlReportDetailRecord(Material material) {
this.material = material;
}
@Override
public void appendTo(Report report) {
report.appendLine(String.format("<tr>%s%s%s%s</tr>",
td(material.getTitle()), td(material
.getAuthor()), td(material.getClassification()),
td(material.getYear())));
}
}
// HtmlReportSummary.java
public class HtmlReportSummary implements ReportComponent {
@Override
public void appendTo(Report report) {
report.appendLine("</table>");
report.appendLine("</body>");
}
}
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This article was originally published on September 4, 2008
