读书笔记_java设计模式深入研究 第六章 桥接模式

1，桥接模式：将抽象部分与实现部分分离，使他们可以独立变化。桥接模式可以实现的是不同方式的组合完成不同的功能，方式和功能完全分离，使得相互不影响。

2，UML模型：

3，简单代码实例：

/**
 *
 * @(#) IPost.java
 * @Package pattern.chp06.bridge.simple
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.simple;

/**
 * 类描述：邮局接口类
 * 
 * @author: Jing
 * @version $Id: Exp$
 * 
 * History: Dec 23, 2014 3:08:36 PM Jing Created.
 * 
 */
public interface IPost {
	/**
	 * 
	 * 方法说明：发送功能
	 * 
	 * Author： Jing Create Date： Dec 23, 2014 3:08:57 PM
	 * 
	 * @return void
	 */
	public void post();
}

/**
 *
 * @(#) MarkPost.java
 * @Package pattern.chp06.bridge.simple
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.simple;


/**
 *  类描述：挂号信
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 23, 2014 3:19:32 PM   Jing   Created.
 *           
 */
public class MarkPost implements IPost{

	public void post() {
		
		System.out.println("This is MarkPost");
	}

}

/**
 *
 * @(#) SimplePost.java
 * @Package pattern.chp06.bridge.simple
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.simple;

/**
 *  类描述：平信邮局
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 23, 2014 3:18:39 PM   Jing   Created.
 *           
 */
public class SimplePost implements IPost{

	public void post() {
		
		System.out.println("This is SimplePost");
	}

}

/**
 *
 * @(#) AbstractThing.java
 * @Package pattern.chp06.bridge.simple
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.simple;

/**
 *  类描述：抽象事物 
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 23, 2014 3:20:37 PM   Jing   Created.
 *           
 */
public abstract class AbstractThing {
	
	private IPost post;

	public AbstractThing(IPost post) {
		this.post = post;
	}
	
	public void post(){
		
		post.post();
	}
	
}

/**
 *
 * @(#) Lettle.java
 * @Package pattern.chp06.bridge.simple
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.simple;

/**
 *  类描述：普通信件 
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 23, 2014 3:21:36 PM   Jing   Created.
 *           
 */
public class Letter extends AbstractThing{

	public Letter(IPost post) {
		super(post);
	}
	
	

}

/**
 *
 * @(#) Parcel.java
 * @Package pattern.chp06.bridge.simple
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.simple;

/**
 *  类描述：挂号
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 23, 2014 3:22:31 PM   Jing   Created.
 *           
 */
public class Parcel extends AbstractThing {

	public Parcel(IPost post) {
		super(post);
	}

}

/**
 *
 * @(#) MainTest.java
 * @Package pattern.chp06.bridge.simple
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.simple;

import org.junit.Test;

/**
 *  类描述：
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 23, 2014 3:23:16 PM   Jing   Created.
 *           
 */
public class MainTest {

	@Test
	public void testMain() throws Exception {
		
		IPost post = new SimplePost();
		Letter letter = new Letter(post);
		
		letter.post();
	}
}

4，深入理解桥接模式

-1，桥接模式强调 包含 替代  继承

这种方式，但对于功能和事物来说两者分离，不会相互影响。

-2，JDK中桥接模式：Collectios.sort方法，借助Arrays.sort方法实现其自身内部的排序。

5，应用

实现读取本地或者远程URL文件，文件类型是文本或图像文件。

分析：

基本到手后实现的思路会如下所示，在TextRead中判断是本地还是URL方法，在其中调用不同的流读写。

但是，当文件类型增多时，会实现多个子类重写，同时会破坏原有方法，需要改进原有方法。我们可以对功能方法进行复杂的拆分，如下UML

代码如下：

/**
 *
 * @(#) Iread.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

/**
 *  类描述：抽象功能类
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 24, 2014 9:41:15 AM   Jing   Created.
 *           
 */
public interface IRead<T> {
	/**
	 * 
	 * 方法说明：文件读取
	 *
	 * Author：       Jing                
	 * Create Date：   Dec 24, 2014 10:52:28 AM
	 *
	 * @return
	 * @throws Exception
	 * @return T
	 */
	T read() throws Exception;
}

/**
 *
 * @(#) TextRead.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

/**
 *  类描述：文本读取
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 24, 2014 10:04:08 AM   Jing   Created.
 *           
 */
public class TextRead implements IRead<String> {
	
	AbstractStream stream;
	public TextRead(AbstractStream stream) {

		this.stream = stream;
	}
	/**
	 * 读取文本文件
	 */
	public String read() throws Exception {
		byte[] buf = stream.readBytes();
		String s = new String(buf);
		return s;
	}

}

/**
 *
 * @(#) ImgRead.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

/**
 * 类描述：读取图像文件
 * 
 * @author: Jing
 * @version $Id: Exp$
 * 
 * History: Dec 24, 2014 10:51:58 AM Jing Created.
 * 
 */
public class ImgRead implements IRead<byte[]> {

	AbstractStream stream;

	public ImgRead(AbstractStream stream) {

		this.stream = stream;
	}

	public byte[] read() throws Exception {

		return stream.readBytes();
	}

}

/**
 *
 * @(#) AbstractStream.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

import java.io.InputStream;

/**
 * 类描述：抽象基类流
 * 
 * @author: Jing
 * @version $Id: Exp$
 * 
 * History: Dec 24, 2014 10:05:54 AM Jing Created.
 * 
 */
public class AbstractStream {

	protected InputStream in;
	protected int size;

	/**
	 * 
	 * 方法说明：读取对应输入流
	 * 
	 * Author： Jing Create Date： Dec 24, 2014 10:11:00 AM
	 * 
	 * @return
	 * @throws Exception
	 * @return byte[]
	 */
	protected byte[] readBytes() throws Exception {

		byte[] buf = new byte[size];
		in.read(buf);
		return buf;
	}

	/**
	 * 
	 * 方法说明：关闭输入流
	 * 
	 * Author： Jing Create Date： Dec 24, 2014 10:11:24 AM
	 * 
	 * @throws Exception
	 * @return void
	 */
	public void close() throws Exception {

		in.close();
	}
}

/**
 *
 * @(#) NativeStream.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

import java.io.File;
import java.io.FileInputStream;

/**
 *  类描述：本地文件流读取
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 24, 2014 10:21:53 AM   Jing   Created.
 *           
 */
public class NativeStream extends AbstractStream{

	public NativeStream(String fileName) throws Exception{
		
		File f = new File(fileName);
		size = (int) f.length();
		in = new FileInputStream(f);
	}
}

/**
 *
 * @(#) URLStream.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

import java.net.HttpURLConnection;
import java.net.URL;

/**
 *  类描述：URl文件读取
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 24, 2014 10:27:09 AM   Jing   Created.
 *           
 */
public class URLStream extends AbstractStream {

	public URLStream(String fileName) throws Exception{
		
		URL url = new URL(fileName);
		in = url.openStream();
		HttpURLConnection urlCon = (HttpURLConnection) url.openConnection();
		size = urlCon.getContentLength();
	}
}

/**
 *
 * @(#) AbstractThing.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

/**
 *  类描述：抽象事务类 
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 24, 2014 10:54:09 AM   Jing   Created.
 *           
 */
public abstract class AbstractThing {
	
	IRead<?> read;

	public AbstractThing(IRead<?> read) {

		this.read = read;
	}
	
	Object read() throws Exception{
		
		return read.read();
	}
}

/**
 *
 * @(#) NativeFile.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

/**
 *  类描述：本地文件读取
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 24, 2014 10:55:59 AM   Jing   Created.
 *           
 */
public class NativeFile  extends AbstractThing{

	public NativeFile(IRead<?> read) {
		super(read);
	}

}

/**
 *
 * @(#) URLFile.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

/**
 * 类描述：URL文件读取
 * 
 * @author: Jing
 * @version $Id: Exp$
 * 
 * History: Dec 24, 2014 10:56:43 AM Jing Created.
 * 
 */
public class URLFile extends AbstractThing {

	public URLFile(IRead<?> read) {
		super(read);
	}

}

/**
 *
 * @(#) Main.java
 * @Package pattern.chp06.bridge.read
 * 
 * Copyright ? JING Corporation. All rights reserved.
 *
 */

package pattern.chp06.bridge.read;

/**
 *  类描述：
 * 
 *  @author:  Jing
 *  @version  $Id: Exp$ 
 *
 *  History:  Dec 24, 2014 11:14:31 AM   Jing   Created.
 *           
 */
public class Main {

	public static void main(String[] args) throws Exception {
		//打开远程文件 
		AbstractStream in = new URLStream("http://js.t.sinajs.cn/t6/webim_prime/js/webim.js?v=1419389776378");
		TextRead textRead = new TextRead(in);
		AbstractThing thing = new URLFile(textRead);
		String s = (String) thing.read();
		in.close();
		
		System.out.println(s);
	}
}