外观模式：在子系统中对一个集合的接口提供同统计的接口，门面定义了能够使子系统更好用更高一级的接口。像spring一样，可以将类和类之间的关系配置到配置文件中，而外观模式就是将他们的关系放在一个Facade类中，降低了类类之间的耦合度。
看一个简单的例子，UML类图如下所示：
ShapeMaker使用了一个具体的类，这个类能够帮助用户调用到所有类的操作。FacadeePatternDemo作为测试类，测试调用功能。
Shape.java
public interface Shape {
void draw();
}
Rectangle.java
public class Rectangle implements Shape {
@Override
public void draw() {
System.out.println("Rectangle::draw()");
}
}
Square.java
public class Square implements Shape {
@Override
public void draw() {
System.out.println("Square::draw()");
}
}
Circle.java
public class Circle implements Shape {
@Override
public void draw() {
System.out.println("Circle::draw()");
}
}
创建Fa?ade类，定义类ShapeMaker.java
public class ShapeMaker {
private Shape circle;
private Shape rectangle;
private Shape square;
public ShapeMaker() {
circle = new Circle();
rectangle = new Rectangle();
square = new Square();
}
public void drawCircle(){
circle.draw();
}
public void drawRectangle(){
rectangle.draw();
}
public void drawSquare(){
square.draw();
}
}
定义测试类FacadePatternDemo
public class FacadePatternDemo {
public static void main(String[] args) {
ShapeMaker shapeMaker = new ShapeMaker();
shapeMaker.drawCircle();
shapeMaker.drawRectangle();
shapeMaker.drawSquare();
}
}
输出结果：
Circle::draw()
Rectangle::draw()
Square::draw()
原文：http://blog.csdn.net/greatelite/article/details/19091059