java 网络编程回顾（一）

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URL回顾：

import java.io.FileOutputStream;import java.io.InputStream;import java.io.OutputStream;import java.net.URL;import java.net.URLConnection;public class URITest {public static void main(String[] args)  throws Exception{URL url = new URL("http://www.hao123.com");URLConnection connection = url.openConnection();InputStream is = connection.getInputStream();OutputStream os = new FileOutputStream("C:/hao123.txt");byte[] buffer = new byte[2048];int length = 0;while(-1 != (length = is.read(buffer, 0, buffer.length))){os.write(buffer, 0, length);}is.close();os.close();}}

另一种方式是通过url的openstream方法直接获得输入流而无需获取connection，内部调用过程是一样的，只不过这种方式少些一行代码：

import java.io.FileOutputStream;import java.io.InputStream;import java.io.OutputStream;import java.net.URL;public class URLTest2 {public static void main(String[] args)  throws Exception{URL url = new URL("http://www.hao123.com");//URLConnection connection = url.openConnection();//InputStream is = connection.getInputStream();OutputStream os = new FileOutputStream("C:/hao1234.html");InputStream is = url.openStream();byte[] buffer = new byte[2048];int length = 0;while(-1 != (length = is.read(buffer, 0, buffer.length))){os.write(buffer, 0, length);}is.close();os.close();}}

查看opensream方法可以看到

 public final InputStream openStream() throws java.io.IOException {return openConnection().getInputStream();    }

   public URLConnection openConnection() throws java.io.IOException {return handler.openConnection(this);    }

abstract protected URLConnection openConnection(URL u) throws IOException;

最终都是通过connection获得。

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