什么是代理模式？

代理模式，一般是为了对真正的对象进行访问限制，延时实例化等，举一个例子： 生活中，书籍厂家生产书并且出售书，但是，如果你想买书的话，一定要到书籍厂家买吗？不是的，我们可以通过大大小小书店购买。 在这里，书籍厂家就是RealObject,它有一个方法sell(); 书店就是代理对象ProxyObject,它也有一个方法sell(),这个方法通过调用realObject的sell()来实现出售书。 下面这个图可以方便我们理解：

如何实现代理模式？

根据上面的讲解，我们来实现一个代理模式：

定义一个Book类：

public class Book implements Parcelable{ private String name; private int price; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getPrice() { return price; } public void setPrice(int price) { this.price = price; } public Book(String name, int price) { this.name = name; this.price = price; } public Book(){ } protected Book(Parcel in) { name = in.readString(); price = in.readInt(); } public static final Creator<Book> CREATOR = new Creator<Book>() { @Override public Book createFromParcel(Parcel in) { return new Book(in); } @Override public Book[] newArray(int size) { return new Book[size]; } }; @Override public int describeContents() { return 0; } @Override public void writeToParcel(Parcel dest, int flags) { dest.writeString(name); dest.writeInt(price); } public void readFromParcel(Parcel dest){ name = dest.readString(); price = dest.readInt(); } @Override public String toString() { StringBuffer string = new StringBuffer(); string.append("name:" + name); string.append("price:" + price); return string.toString(); } } 定义IBookFactory接口：

public interface IBookFactory { Book sell(); } 定义BookFactory类：

public class BookFactory implements IBookFactory{ private List<Book> books = new ArrayList<>(); public BookFactory() { for(int i=0;i<10;i++){ books.add(new Book("book" + i, i * 100)); } } @Override public Book sell() { if(books.size() > 0){ return books.remove(books.size()-1); } return null; } }定义ProxyBookFactory类：

public class ProxyBookFactory implements IBookFactory { private BookFactory bookFactory; public ProxyBookFactory() { bookFactory = new BookFactory(); } @Override public Book sell() { return bookFactory.sell(); } }定义BookCustomer类：

public class BookCustomer { private ProxyBookFactory proxyBookFactory; public void setProxyObject(ProxyBookFactory proxyObject) { this.proxyBookFactory = proxyObject; } public ProxyBookFactory getProxyObject() { return proxyBookFactory; } public Book buyBook(){ return proxyBookFactory.sell(); } } 定义调用函数:

public class Main { public static void main(String[] args){ BookCustomer bookCustomer = new BookCustomer(); ProxyBookFactory proxyBookFactory = new ProxyBookFactory(); bookCustomer.setProxyObject(proxyBookFactory); Book book = bookCustomer.buyBook(); System.out.println(book == null ? "null" : book.toString()); } }

参考了：http://blog.csdn.net/hguisu/article/details/7542143

参考了：http://www.cnblogs.com/java-my-life/archive/2012/04/23/2466712.html