简单介绍Java网络编程中的HTTP请求

import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL;   public class Http_Get {    private static String URL_PATH = "http://192.168.1.125:8080/myhttp/pro1.png";    public Http_Get() {     // TODO Auto-generated constructor stub   }    public static void saveImageToDisk() {     InputStream inputStream = getInputStream();     byte[] data = new byte[1024];     int len = 0;     FileOutputStream fileOutputStream = null;     try {       fileOutputStream = new FileOutputStream("C://test.png");       while ((len = inputStream.read(data)) != -1) {         fileOutputStream.write(data, 0, len);       }     } catch (IOException e) {       // TODO Auto-generated catch block       e.printStackTrace();     } finally {       if (inputStream != null) {         try {           inputStream.close();         } catch (IOException e) {           // TODO Auto-generated catch block           e.printStackTrace();         }       }       if (fileOutputStream != null) {         try {           fileOutputStream.close();         } catch (IOException e) {           // TODO Auto-generated catch block           e.printStackTrace();         }       }     }   }    /**    * 获得服务器端的数据,以InputStream形式返回    * @return    */   public static InputStream getInputStream() {     InputStream inputStream = null;     HttpURLConnection httpURLConnection = null;     try {       URL url = new URL(URL_PATH);       if (url != null) {         httpURLConnection = (HttpURLConnection) url.openConnection();         // 设置连接网络的超时时间         httpURLConnection.setConnectTimeout(3000);         httpURLConnection.setDoInput(true);         // 表示设置本次http请求使用GET方式请求         httpURLConnection.setRequestMethod("GET");         int responseCode = httpURLConnection.getResponseCode();         if (responseCode == 200) {           // 从服务器获得一个输入流           inputStream = httpURLConnection.getInputStream();         }       }     } catch (MalformedURLException e) {       // TODO Auto-generated catch block       e.printStackTrace();     } catch (IOException e) {       // TODO Auto-generated catch block       e.printStackTrace();     }     return inputStream;   }    public static void main(String[] args) {     // 从服务器获得图片保存到本地     saveImageToDisk();   } } 

import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.UnsupportedEncodingException; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.net.URLEncoder; import java.util.HashMap; import java.util.Map;  public class Http_Post {    // 请求服务器端的url   private static String PATH = "http://192.168.1.125:8080/myhttp/servlet/LoginAction";   private static URL url;    public Http_Post() {     // TODO Auto-generated constructor stub   }    static {     try {       url = new URL(PATH);     } catch (MalformedURLException e) {       // TODO Auto-generated catch block       e.printStackTrace();     }   }    /**    * @param params    *      填写的url的参数    * @param encode    *      字节编码    * @return    */   public static String sendPostMessage(Map<String, String> params,       String encode) {     // 作为StringBuffer初始化的字符串     StringBuffer buffer = new StringBuffer();     try {       if (params != null && !params.isEmpty()) {          for (Map.Entry<String, String> entry : params.entrySet()) {             // 完成转码操作             buffer.append(entry.getKey()).append("=").append(                 URLEncoder.encode(entry.getValue(), encode))                 .append("&");           }         buffer.deleteCharAt(buffer.length() - 1);       }       // System.out.println(buffer.toString());       // 删除掉最有一个&              System.out.println("-->>"+buffer.toString());       HttpURLConnection urlConnection = (HttpURLConnection) url           .openConnection();       urlConnection.setConnectTimeout(3000);       urlConnection.setRequestMethod("POST");       urlConnection.setDoInput(true);// 表示从服务器获取数据       urlConnection.setDoOutput(true);// 表示向服务器写数据       // 获得上传信息的字节大小以及长度       byte[] mydata = buffer.toString().getBytes();       // 表示设置请求体的类型是文本类型       urlConnection.setRequestProperty("Content-Type",           "application/x-www-form-urlencoded");       urlConnection.setRequestProperty("Content-Length",           String.valueOf(mydata.length));       // 获得输出流,向服务器输出数据       OutputStream outputStream = urlConnection.getOutputStream();       outputStream.write(mydata,0,mydata.length);       outputStream.close();       // 获得服务器响应的结果和状态码       int responseCode = urlConnection.getResponseCode();       if (responseCode == 200) {         return changeInputStream(urlConnection.getInputStream(), encode);       }     } catch (UnsupportedEncodingException e) {       // TODO Auto-generated catch block       e.printStackTrace();     } catch (IOException e) {       // TODO Auto-generated catch block       e.printStackTrace();     }     return "";   }    /**    * 将一个输入流转换成指定编码的字符串    *    * @param inputStream    * @param encode    * @return    */   private static String changeInputStream(InputStream inputStream,       String encode) {     // TODO Auto-generated method stub     ByteArrayOutputStream outputStream = new ByteArrayOutputStream();     byte[] data = new byte[1024];     int len = 0;     String result = "";     if (inputStream != null) {       try {         while ((len = inputStream.read(data)) != -1) {           outputStream.write(data, 0, len);         }         result = new String(outputStream.toByteArray(), encode);       } catch (IOException e) {         // TODO Auto-generated catch block         e.printStackTrace();       }     }     return result;   }    /**    * @param args    */   public static void main(String[] args) {     // TODO Auto-generated method stub     Map<String, String> params = new HashMap<String, String>();     params.put("username", "admin");     params.put("password", "123");     String result = Http_Post.sendPostMessage(params, "utf-8");     System.out.println("--result->>" + result);   }  }