门面模式/外观模式

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#设计模式

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为子系统中一组接口提供一个一致的界面，此模式定义一个高级接口，这个接口使得这一子系统更加容易使用。

案例1

public class SubSystem1 {
    public void methodOne(){
        System.out.println("子系统方法一");
    }
}

public class SubSystem2 {
    public void methodTwo(){
        System.out.println("子系统方法二");
    }
}


public class SubSystem3 {

    public void methodThree(){
        System.out.println("子系统方法三");
    }
}


public class Facade {

    SubSystem1 subSystem1 ;
    SubSystem2 subSystem2;
    SubSystem3 subSystem3;

    public Facade(){
        subSystem1 =  new SubSystem1();
        subSystem2 = new SubSystem2();
        subSystem3 = new SubSystem3();
    }

    public  void methodA(){
        System.out.println("\n方法组A:");
        subSystem1.methodOne();
        subSystem3.methodThree();
    }

    public void methodB(){
        System.out.println("\n方法组B:");
        subSystem2.methodTwo();
        subSystem3.methodThree();
    }

}

public class TestMainFacade {

    public  static  void main(String[] args){
        Facade facade = new Facade();
        facade.methodA();
        facade.methodB();
    }
}

结果：

/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/bin/java "-javaagent:/Applications/IntelliJ IDEA CE.app/Contents/lib/idea_rt.jar=50254:/Applications/IntelliJ IDEA CE.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/tools.jar:/Users/liuxuwei/IdeaProjects/dahuadesignmodel/out/production/dahuadesignmodel facademodel7.base7.TestMainFacade

方法组A:
子系统方法一
子系统方法三

方法组B:
子系统方法二
子系统方法三

Process finished with exit code 0

在设计初期阶段，应该有意识的将不同的两个层分离，层与层之间建立三层架构；

在开发阶段，增加外观facade，减少子系统之间依赖；

维护大型遗留系统时，在和新系统交互时，可以提供老系统一个facade接口；

案例2

public class Realty1 {

    public  void sell(){
        System.out.println("房地产1卖出");
    }

    public  void buy(){
        System.out.println("房地产1买入");
    }

}

public class NationalDebt1 {

    public  void sell(){
        System.out.println("国债1卖出");
    }

    public  void buy(){
        System.out.println("国债1买入");
    }
}


public class Stock1 {

    public  void sell(){
        System.out.println("股票1卖出");
    }

    public  void buy(){
        System.out.println("股票1买入");
    }

}

public class Stock2 {

    public  void sell(){
        System.out.println("股票2卖出");
    }

    public  void buy(){
        System.out.println("股票2买入");
    }
}

public class Stock3 {

    public  void sell(){
        System.out.println("股票3卖出");
    }

    public  void buy(){
        System.out.println("股票3买入");
    }
}

public class Fund {

    Stock1 stock1;
    Stock2 stock2;
    Stock3 stock3;
    NationalDebt1 nationalDebt1;
    Realty1 realty1;

    public Fund(){
        stock1 = new Stock1();
        stock2 = new Stock2();
        stock3 = new Stock3();
        nationalDebt1 = new NationalDebt1();
        realty1 = new Realty1();
    }

    public void buyFund(){
        stock1.buy();
        stock2.buy();
        stock3.buy();
        nationalDebt1.buy();
        realty1.buy();
    }

    public void SellFund(){
        stock1.sell();
        stock2.sell();
        stock3.sell();
        nationalDebt1.sell();
        realty1.sell();
    }


}

public class FundTestMain {

    public static  void main(String[] args){
        Fund jijin = new Fund();
        jijin.buyFund();
        jijin.SellFund();

    }
}

结果如下：

/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/bin/java "-javaagent:/Applications/IntelliJ IDEA CE.app/Contents/lib/idea_rt.jar=50422:/Applications/IntelliJ IDEA CE.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_241.jdk/Contents/Home/lib/tools.jar:/Users/liuxuwei/IdeaProjects/dahuadesignmodel/out/production/dahuadesignmodel facademodel7.FundTestMain
股票1买入
股票2买入
股票3买入
国债1买入
房地产1买入
股票1卖出
股票2卖出
股票3卖出
国债1卖出
房地产1卖出

Process finished with exit code 0

参考《大话设计模式》