本文翻译自：https://www.journaldev.com/1418/abstract-factory-design-pattern-in-java
Abstract Factory
如果你熟悉工厂方法模式（工厂模式），你会注意到我们只有一个工厂类，这个工厂类返回一个对象是基于你的输入，然后做if-else判断得到的。然而在抽象工厂模式中，我们将摆脱这种方式，会基于输入的工厂类型来做相应的输出；看起来是更加复杂了，但是一旦掌握了，你会觉得它很简单；so easy!
Abstract Factory Design Pattern Super Class and Subclasses
Computer.java
package com.journaldev.design.model;
public abstract class Computer {
public abstract String getRAM();
public abstract String getHDD();
public abstract String getCPU();
@Override
public String toString(){
return "RAM= "+this.getRAM()+", HDD="+this.getHDD()+", CPU="+this.getCPU();
}
}
PC.java
package com.journaldev.design.model;
public class PC extends Computer {
private String ram;
private String hdd;
private String cpu;
public PC(String ram, String hdd, String cpu){
this.ram=ram;
this.hdd=hdd;
this.cpu=cpu;
}
@Override
public String getRAM() {
return this.ram;
}
@Override
public String getHDD() {
return this.hdd;
}
@Override
public String getCPU() {
return this.cpu;
}
}
Server.java
package com.journaldev.design.model;
public class Server extends Computer {
private String ram;
private String hdd;
private String cpu;
public Server(String ram, String hdd, String cpu){
this.ram=ram;
this.hdd=hdd;
this.cpu=cpu;
}
@Override
public String getRAM() {
return this.ram;
}
@Override
public String getHDD() {
return this.hdd;
}
@Override
public String getCPU() {
return this.cpu;
}
}
Factory Class for Each subclass(针对每一个子类的工厂类)
ComputerAbstractFactory.java
package com.journaldev.design.abstractfactory;
import com.journaldev.design.model.Computer;
public interface ComputerAbstractFactory {
public Computer createComputer();
}
注意createComputer() 方法的返回类型是Computer，之后的工厂类将会实现这个接口；
PCFactory.java
package com.journaldev.design.abstractfactory;
import com.journaldev.design.model.Computer;
import com.journaldev.design.model.PC;
public class PCFactory implements ComputerAbstractFactory {
private String ram;
private String hdd;
private String cpu;
public PCFactory(String ram, String hdd, String cpu){
this.ram=ram;
this.hdd=hdd;
this.cpu=cpu;
}
@Override
public Computer createComputer() {
return new PC(ram,hdd,cpu);
}
}
ServerFactory.java
package com.journaldev.design.abstractfactory;
import com.journaldev.design.model.Computer;
import com.journaldev.design.model.Server;
public class ServerFactory implements ComputerAbstractFactory {
private String ram;
private String hdd;
private String cpu;
public ServerFactory(String ram, String hdd, String cpu){
this.ram=ram;
this.hdd=hdd;
this.cpu=cpu;
}
@Override
public Computer createComputer() {
return new Server(ram,hdd,cpu);
}
}
ComputerFactory.java
package com.journaldev.design.abstractfactory;
import com.journaldev.design.model.Computer;
public class ComputerFactory {
public static Computer getComputer(ComputerAbstractFactory factory){
return factory.createComputer();
}
}
注意到这个是简单的类，getComputer方法的参数是ComputerAbstractFactory，至此整个实现需要简洁明了；接下来请看一个小测试：
TestDesignPatterns.java
package com.journaldev.design.test;
import com.journaldev.design.abstractfactory.PCFactory;
import com.journaldev.design.abstractfactory.ServerFactory;
import com.journaldev.design.factory.ComputerFactory;
import com.journaldev.design.model.Computer;
public class TestDesignPatterns {
public static void main(String[] args) {
testAbstractFactory();
}
private static void testAbstractFactory() {
Computer pc = ComputerFactory.getComputer(new PCFactory("2 GB","500 GB","2.4 GHz"));
Computer server = ComputerFactory.getComputer(new ServerFactory("16 GB","1 TB","2.9 GHz"));
System.out.println("AbstractFactory PC Config::"+pc);
System.out.println("AbstractFactory Server Config::"+server);
}
}
输出结果：
AbstractFactory PC Config::RAM= 2 GB, HDD=500 GB, CPU=2.4 GHz
AbstractFactory Server Config::RAM= 16 GB, HDD=1 TB, CPU=2.9 GHz
Abstract Factory Design Pattern Examples in JDK（抽象工厂模式在JDK中的运用）
- javax.xml.parsers.DocumentBuilderFactory#newInstance()
- javax.xml.transform.TransformerFactory#newInstance()
- javax.xml.xpath.XPathFactory#newInstance()
