//: builder:BuildMedia.java
// Example of the Builder pattern
package builder;
import java.util.*;
import junit.framework.*;
// Different "representations" of media:
class Media extends ArrayList {}
class Book extends Media {}
class Magazine extends Media {}
class WebSite extends Media {}
// ... contain different kinds of media items:
class MediaItem {
private String s;
public MediaItem(String s) { this.s = s; }
public String toString() { return s; }
}
class Chapter extends MediaItem {
public Chapter(String s) { super(s); }
}
class Article extends MediaItem {
public Article(String s) { super(s); }
}
class WebItem extends MediaItem {
public WebItem(String s) { super(s); }
}
// ... but use the same basic construction steps:
class MediaBuilder {
public void buildBase() {}
public void addMediaItem(MediaItem item) {}
public Media getFinishedMedia() { return null; }
}
class BookBuilder extends MediaBuilder {
private Book b;
public void buildBase() {
System.out.println("Building book framework");
b = new Book();
}
public void addMediaItem(MediaItem chapter) {
System.out.println("Adding chapter " + chapter);
b.add(chapter);
}
public Media getFinishedMedia() { return b; }
}
class MagazineBuilder extends MediaBuilder {
private Magazine m;
public void buildBase() {
System.out.println("Building magazine framework");
m = new Magazine();
}
public void addMediaItem(MediaItem article) {
System.out.println("Adding article " + article);
m.add(article);
}
public Media getFinishedMedia() { return m; }
}
class WebSiteBuilder extends MediaBuilder {
private WebSite w;
public void buildBase() {
System.out.println("Building web site framework");
w = new WebSite();
}
public void addMediaItem(MediaItem webItem) {
System.out.println("Adding web item " + webItem);
w.add(webItem);
}
public Media getFinishedMedia() { return w; }
}
class MediaDirector { // a.k.a. "Context"
private MediaBuilder mb;
public MediaDirector(MediaBuilder mb) {
this.mb = mb; // Strategy-ish
}
public Media produceMedia(List input) {
mb.buildBase();
for(Iterator it = input.iterator(); it.hasNext();)
mb.addMediaItem((MediaItem)it.next());
return mb.getFinishedMedia();
}
};
public class BuildMedia extends TestCase {
private List input = Arrays.asList(new MediaItem[] {
new MediaItem("item1"), new MediaItem("item2"),
new MediaItem("item3"), new MediaItem("item4"),
});
public void testBook() {
MediaDirector buildBook =
new MediaDirector(new BookBuilder());
Media book = buildBook.produceMedia(input);
String result = "book: " + book;
System.out.println(result);
assertEquals(result,
"book: [item1, item2, item3, item4]");
}
public void testMagazine() {
MediaDirector buildMagazine =
new MediaDirector(new MagazineBuilder());
Media magazine = buildMagazine.produceMedia(input);
String result = "magazine: " + magazine;
System.out.println(result);
assertEquals(result,
"magazine: [item1, item2, item3, item4]");
}
public void testWebSite() {
MediaDirector buildWebSite =
new MediaDirector(new WebSiteBuilder());
Media webSite = buildWebSite.produceMedia(input);
String result = "web site: " + webSite;
System.out.println(result);
assertEquals(result,
"web site: [item1, item2, item3, item4]");
}
public static void main(String[] args) {
junit.textui.TestRunner.run(BuildMedia.class);
}
} ///:~
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