Factory Method概述

Factory Method - 图1

玩具代码案例 - 文件编辑器

工厂方法抽象父类

Editor

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.creator.api;
  3. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.api.Document;
  5. import java.util.ArrayList;
  6. import java.util.List;
  8. public abstract class Editor {
  10.     private String title;
  12.     private Document current;
  14.     private List<Document> documents = new ArrayList<>();
  16.     public String getTitle() {
  17.         return title;
  18.     }
  20.     public void setTitle(String title) {
  21.         this.title = title;
  22.     }
  24.     public void open(String file) {
  25.         setTitle(file);
  26.         current = createDocument(file);
  27.         current.open();
  28.         current.display();
  30.         // multi-documents
  31.         documents.add(current);
  32.     }
  34.     public void save() {
  35.         current.save();
  36.     }
  38.     public void close() {
  39.         current.close();
  40.     }
  42.     public void saveAll() {
  43.         for (Document document : documents) {
  44.             document.save();
  45.         }
  46.     }
  48.     public void closeAll() {
  49.         for (Document document : documents) {
  50.             document.close();
  51.         }
  52.     }
  54.     // Factory method
  55.     protected abstract Document createDocument(String file);
  56. }

工厂方法具体子类

PdfEditor

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.creator.impl;
  3. import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.api.Editor;
  4. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.api.Document;
  5. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl.PdfDocument;
  7. public class PdfEditor extends Editor {
  9.     protected Document createDocument(String file) {
  10.         Document document = new PdfDocument();
  11.         document.setFile(file);
  12.         return document;
  13.     }
  14. }

PngEditor

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.creator.impl;
  3. import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.api.Editor;
  4. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.api.Document;
  5. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl.PngDocument;
  7. public class PngEditor extends Editor {
  9.     protected Document createDocument(String file) {
  10.         Document document = new PngDocument();
  11.         document.setFile(file);
  12.         return document;
  13.     }
  14. }

TxtEditor

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.creator.impl;
  3. import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.api.Editor;
  4. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.api.Document;
  5. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl.TxtDocument;
  7. public class TxtEditor extends Editor {
  9.     protected Document createDocument(String file) {
  10.         Document document = new TxtDocument();
  11.         document.setFile(file);
  12.         return document;
  13.     }
  14. }

产品接口

Document

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.product.api;
  3. public abstract class Document {
  5.     private String file;
  7.     public String getFile() {
  8.         return file;
  9.     }
  11.     public void setFile(String file) {
  12.         this.file = file;
  13.     }
  15.     public abstract void open();
  17.     public abstract void display();
  19.     public abstract void save();
  21.     public abstract void close();
  22. }

具体产品

PdfDocument

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl;
  3. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.api.Document;
  5. public class PdfDocument extends Document {
  7.     public PdfDocument(){
  9.     }
  11.     @Override
  12.     public void open() {
  13.         System.out.println("打开Pdf文件" + this.getFile());
  14.     }
  16.     @Override
  17.     public void display()  {
  18.         System.out.println("显示Pdf文件" + this.getFile());
  19.     }
  21.     @Override
  22.     public void save() {
  23.         System.out.println("存储Pdf文件" + this.getFile());
  24.     }
  26.     @Override
  27.     public void close() {
  28.         System.out.println("关闭Pdf文件" + this.getFile());
  29.     }
  30. }

PngDocument

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl;
  3. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.api.Document;
  5. public class PngDocument extends Document {
  7.     public PngDocument(){
  9.     }
  11.     @Override
  12.     public void open() {
  13.         System.out.println("打开PNG文件" + this.getFile());
  14.     }
  16.     @Override
  17.     public void display()  {
  18.         System.out.println("显示PNG文件" + this.getFile());
  19.     }
  21.     @Override
  22.     public void save() {
  23.         System.out.println("存储PNG文件" + this.getFile());
  24.     }
  26.     @Override
  27.     public void close() {
  28.         System.out.println("关闭PNG文件" + this.getFile());
  29.     }
  30. }

TxtDocument

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl;
  3. import online.javabook.gof.creational.patterns3.factorymethod.editor.product.api.Document;
  5. public class TxtDocument extends Document {
  7.     public TxtDocument(){
  9.     }
  11.     @Override
  12.     public void open() {
  13.         System.out.println("打开Txt文件" + this.getFile());
  14.     }
  16.     @Override
  17.     public void display()  {
  18.         System.out.println("显示Txt文件" + this.getFile());
  19.     }
  21.     @Override
  22.     public void save() {
  23.         System.out.println("存储Txt文件" + this.getFile());
  24.     }
  26.     @Override
  27.     public void close() {
  28.         System.out.println("关闭Txt文件" + this.getFile());
  29.     }
  30. }

基于工厂方法模式的实现 - 仅支持单一文件类型的工厂方法编辑器

SingleEditorMain

  1. package online.javabook.gof.creational.patterns3.factorymethod.editor.app.good;
  3. import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.api.Editor;
  4. import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.impl.PdfEditor;
  5. import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.impl.PngEditor;
  6. import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.impl.TxtEditor;
  8. public class SingleEditorMain {
  9.     public static void main(String[] args) {
  11.         // product
  12.         String fileName = "*.txt";
  14.         // factory
  15.         Editor editor = null;
  16.         if (fileName.endsWith(".txt")) {
  17.             editor = new TxtEditor();
  19.         } else if (fileName.endsWith(".pdf")) {
  20.             editor = new PdfEditor();
  22.         }else if (fileName.endsWith(".png")) {
  23.             editor = new PngEditor();
  24.         }
  26.         // do business
  27.         editor.open("file1.txt");
  28.         editor.open("file2.txt");
  29.         editor.open("file3.txt");
  31.         System.out.println("最后一次打开的文件:" +editor.getTitle());
  32.         editor.saveAll();
  33.         editor.closeAll();
  34.     }
  35. }

Console

  1. 打开Txt文件file1.txt
  2. 显示Txt文件file1.txt
  3. 打开Txt文件file2.txt
  4. 显示Txt文件file2.txt
  5. 打开Txt文件file3.txt
  6. 显示Txt文件file3.txt
  7. 最后一次打开的文件:file3.txt
  8. 存储Txt文件file1.txt
  9. 存储Txt文件file2.txt
  10. 存储Txt文件file3.txt
  11. 关闭Txt文件file1.txt
  12. 关闭Txt文件file2.txt
  13. 关闭Txt文件file3.txt

基于工厂方法模式的实现 - 支持类型注册与多种文件类型的工厂方法编辑器

MultiEditor

package online.javabook.gof.creational.patterns3.factorymethod.editor.creator.impl;

import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.api.Editor;
import online.javabook.gof.creational.patterns3.factorymethod.editor.product.api.Document;
import org.apache.commons.io.FilenameUtils;

import java.util.HashMap;
import java.util.Map;

public class MultiEditor extends Editor {

    private Map<String, Class<? extends Document>> registers = new HashMap<>();

    // register methods
    public <T extends Class<? extends Document>> void registerDocumentClass(String extension, T documentClass) {
        registers.put(extension, documentClass);
    }

    protected Class<? extends Document> getRegisteredDocumentClass(String extension) {
        Class<? extends Document> documentClass = registers.get(extension);
        return documentClass;
    }

    // Factory method
    protected Document createDocument(String fileName) {

        String extension = FilenameUtils.getExtension(fileName);
        Class<? extends Document> documentClass = getRegisteredDocumentClass(extension);

        Document document = null;
        try {
            document = documentClass.newInstance();
            document.setFile(fileName);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return document;
    }
}

MultiEditorMain

package online.javabook.gof.creational.patterns3.factorymethod.editor.app.good;

import online.javabook.gof.creational.patterns3.factorymethod.editor.creator.impl.MultiEditor;
import online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl.PdfDocument;
import online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl.PngDocument;
import online.javabook.gof.creational.patterns3.factorymethod.editor.product.impl.TxtDocument;

public class MultiEditorMain {
    public static void main(String[] args) {

        // factory
        MultiEditor editor = new MultiEditor();
        editor.registerDocumentClass("txt", TxtDocument.class);
        editor.registerDocumentClass("pdf", PdfDocument.class);
        editor.registerDocumentClass("png", PngDocument.class);

        // do business
        editor.open("file1.txt");
        editor.open("file2.pdf");
        editor.open("file3.png");

        System.out.println("最后一次打开的文件:" +editor.getTitle());
        editor.saveAll();
        editor.closeAll();
    }
}

Console

打开Txt文件file1.txt
显示Txt文件file1.txt
打开Pdf文件file2.pdf
显示Pdf文件file2.pdf
打开PNG文件file3.png
显示PNG文件file3.png
最后一次打开的文件:file3.png
存储Txt文件file1.txt
存储Pdf文件file2.pdf
存储PNG文件file3.png
关闭Txt文件file1.txt
关闭Pdf文件file2.pdf
关闭PNG文件file3.png