模拟客户端与服务器端交互--包含字符流向字节流转型的使用

本文通过一个简单的示例介绍了如何使用Java实现HTTP客户端与服务器之间的数据交互，包括客户端发送请求及服务器响应的过程。

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1.首先我们建立一个Web工程，TestDemoProject

2.在com.test.chapter01包下创建一个Servlet，ServerDemo.java，并且在web.xml中配置如下：

<servlet-name>ServerDemo</servlet-name>

<servlet-class>com.test.chapter01.ServerDemo</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>ServerDemo</servlet-name>

<url-pattern>/helloServlet</url-pattern>

</servlet-mapping>

该Servlet中代码如下：

package com.test.chapter01;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.PrintWriter;

import javax.servlet.Servlet;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

* 服务器端接收数据并返回数据给客户端

* <数据之间一般用XML进行交互>

* @author XXX

* @version XXX

* @see [相关类/方法]

* @since [产品/模块版本]

public class ServerDemo extends HttpServlet implements Servlet

{

private static final long serialVersionUID = 1L;

//通讯换行符。

private final static String NEW_LINE = "/r/n";

/**

* doGet()方法

protected void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException

{

this.doPost(request, response);

}

/**

* doGet()方法

protected void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException

{

InputStream is = null;

BufferedReader reader = null;

PrintWriter out = null;

try

{

is = request.getInputStream();

reader = new BufferedReader(new InputStreamReader(is));

StringBuffer sb = new StringBuffer();

String content = reader.readLine();

while (null != content)

{

sb.append(content + NEW_LINE);

content = reader.readLine();

}

System.out.println("request message is: " + sb.toString());

out = response.getWriter();

out.write("Hello World!");

}

catch (Exception e)

{

e.printStackTrace();

}

finally

{

if (null != out)

{

out.flush();

out.close();

}

if (null != reader)

{

reader.close();

}

if (null != is)

{

is.close();

}

3.编写客户端与服务器端交互的工具类

package com.test.chapter01;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.OutputStreamWriter;

import java.io.Writer;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLConnection;

/**

* 客户端访问服务器端的工具类

* @author XXX

* @version XXX

* @see [相关类/方法]

* @since [产品/模块版本]

public class ServerTools

{

//通讯换行符。

private final static String NEW_LINE = "/r/n";

/**

* 访问服务器端的URL

private String url;

public String getUrl()

{

return url;

}

public void setUrl(String url)

{

this.url = url;

}

/**

* 校验URL是否合理

* @return URL是否合理

* @see [类、类#方法、类#成员]

public boolean isValidURL()

{

try

{

URL url = new URL(this.getUrl());

if (null != url)

{

return true;

}

catch (MalformedURLException e)

{

e.printStackTrace();

}

return false;

}

/**

* 发送消息到服务器端，并且接受服务端响应的消息(如果有)

* @param message 需要发送的消息

* @return String 服务器端响应的消息

* @see [类、类#方法、类#成员]

public String sendAndReceiveMessage(String message)

{

StringBuffer sb = new StringBuffer();

URL url = null;

Writer writer = null;

BufferedReader reader = null;

HttpURLConnection urlConnection = null;

try

{

url = new URL(this.getUrl());

//打开URL链接

URLConnection connection = url.openConnection();

//设置连接超时最大的毫秒数，这里设置超时时间为2分钟

connection.setConnectTimeout(1000 * 60 * 2);

//需要写入数据

connection.setDoOutput(true);

//需要从URL连接中读取数据

connection.setDoInput(true);

//向URL中写入数据，需要将字符流转换成字节流

writer = new OutputStreamWriter(connection.getOutputStream());

writer.write(message);

writer.flush();

//写完数据之后，需要从连接中读取服务器返回的数据

reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));

String content = reader.readLine();

while (null != content)

{

sb.append(content + NEW_LINE);

content = reader.readLine();

}

//检查通信结果

urlConnection = (HttpURLConnection)connection;

if (HttpURLConnection.HTTP_OK != urlConnection.getResponseCode())

{

throw new IllegalStateException("response code error --> " + urlConnection.getResponseCode());

}

System.out.println("response message is: " + sb.toString());

}

catch (MalformedURLException e)

{

e.printStackTrace();

}

catch (IOException e)

{

e.printStackTrace();

}

finally

{

if (null != writer)

{

try

{

writer.flush();

writer.close();

}

catch (IOException e)

{

e.printStackTrace();

}

if (null != reader)

{

try

{

reader.close();

}

catch (IOException e)

{

e.printStackTrace();

}

//断开连接

if (null != urlConnection)

{

urlConnection.disconnect();

}

return sb.toString();

}

4.编写测试数据类

package com.test.chapter01;

/**

* 测试类

* @author XXX

* @version XXX

* @see [相关类/方法]

* @since [产品/模块版本]

public class Test

{

public static void main(String[] args)

{

String requestUrl = "http://localhost:8081/TestDemoProject/helloServlet";

ServerTools tools = new ServerTools();

tools.setUrl(requestUrl);

boolean isValidUrl = tools.isValidURL();

if (isValidUrl)

{

String receiveMessage = tools.sendAndReceiveMessage("lenbo");

System.out.println(receiveMessage);

}

5.将TestDemoProject发布到Tomcat中，启动Tomcat(我本地端口号为8081)，执行main方法就可以模拟到从服务器端返回的数据了，这个例子模拟了客户端访问服务器的整个过程，同时结合了字符流向字节流转换的应用，简化了数据的操作。

response message is: Hello World!

Hello World!