设计模式（二）
外观模式(Facade)
为了解决子系统外部的客户端在使用子系统的时候，既能简单地使用这些子系统内部的模块功能，而又不用客户端去与子系统内部的多个模块交互的问题。
为子系统中的一组接口提供一个一致的界面，外观模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。
外观模式就是通过引入一个外观类，在这个类里面定义客户端想要的简单的方法，然后在这些方法的实现里面，由外观类再去分别调用内部的多个模块来实现功能，从而让客户端变得简单。这样一来，客户端就只需要和外观类交互就可以了。
package Facade;
public classConfigModel {
private boolean needGenPresentation = true;
private boolean needGenBusiness = true;
private boolean needGenDAO = true;
public boolean isNeedGenPresentation(){
return needGenPresentation;
}
public boolean isNeedGenBusiness(){
return needGenBusiness;
}
public boolean isNeedGenDAO(){
return needGenDAO;
}
public void setNeedGenPresentation(boolean needGenPresentation){
this.needGenPresentation=needGenPresentation;
}
public void setNeedGenBusiness(boolean needGenBusiness){
this.needGenBusiness=needGenBusiness;
}
public void setNeedGenDAO(boolean needGenDAO){
this.needGenDAO=needGenDAO;
}
}
package Facade;
public classConfigManager {
private static ConfigManager manager = null;
private static ConfigModel cm = null;
private ConfigManager(){
//
}
public static ConfigManager getInstance(){
if(manager==null){
manager = new ConfigManager();
cm = new ConfigModel();
}
return manager;
}
public ConfigModel getConfigDate(){
return cm;
}
}
package Facade;
public classPresentation {
public void generate(){
ConfigModel cm = ConfigManager.getInstance().getConfigDate();
if(cm.isNeedGenPresentation()){
System.out.println("Generate Presentation Layer");
}
}
}
package Facade;
public classBusiness {
public void generate(){
ConfigModel cm = ConfigManager.getInstance().getConfigDate();
if(cm.isNeedGenBusiness()){
System.out.println("Generate Business Layer");
}
}
}
package Facade;
public classDAO {
public void generate(){
ConfigModel cm = ConfigManager.getInstance().getConfigDate();
if(cm.isNeedGenDAO()){
System.out.println("Generate DAO Layer");
}
}
}
package Facade;
public classFacade {
publicvoidgenerate(){
new Presentation().generate();
new Business().generate();
new DAO().generate();
}
}
package Facade;
public classClient {
publicstaticvoidmain(String[] args){
new Facade().generate();
}
}
Output:
Generate Presentation Layer
Generate Business Layer
Generate DAO Layer