HttpURLConnection使用示例

public abstract class HttpURLConnection extends URLConnection

支持 HTTP 特定功能的 URLConnection，如设置请求方法（GET、POST等）

每个 HttpURLConnection 实例都可用于生成单个请求，但是其他实例可以透明地共享连接到 HTTP 服务器的基础网络。请求后在 HttpURLConnection 的 InputStream 或 OutputStream 上调用 close() 方法可以释放与此实例关联的网络资源，但对共享的持久连接没有任何影响。如果在调用 disconnect() 时持久连接空闲，则可能关闭基础套接字。

模拟表单发送GET、POST请求

设置请求方法：setRequestMethod(String method)，默认值：GET，可选值：GET 、POST 、HEAD 、OPTIONS、PUT、DELETE 、TRACE

1.GET请求

public static String doGet(String url, String params) {BufferedReader in = null;try {String urlString = url + "?" + params;URL realUrl = new URL(urlString);// 打开和URL之间的连接HttpURLConnection conn = (HttpURLConnection) realUrl.openConnection();// 设置请求参数conn.setRequestMethod("GET");// 默认GET，可以不填conn.setUseCaches(false);conn.setConnectTimeout(5000); //请求超时时间// 设置请求属性conn.setRequestProperty("accept", "*/*");conn.setRequestProperty("connection", "Keep-Alive");// conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");// 建立实际的连接conn.connect();// 获取所有响应头Map<String, List<String>> map = conn.getHeaderFields();for (String key : map.keySet()) {System.out.println(key + "=" + map.get(key));}// 获取响应String line = null;StringBuffer sb = new StringBuffer();in = new BufferedReader(new InputStreamReader(conn.getInputStream()));while ((line = in.readLine()) != null) {sb.append(line);}return sb.toString();} catch (Exception e) {e.printStackTrace();} finally {try {if (in != null) {in.close();in = null;}} catch (Exception e) {e.printStackTrace();}}return null;}

2.POST请求

模拟发送POST请求，需要设置：

• conn.setDoInput(true)，true：从URL连接读取数据
• conn.setDoOutput(true)，true：数据写入URL连接

若有参数，建议设置conn.setRequestProperty("Content-Type", xxx)，常用值：

• application/x-www-form-urlencoded; charset=UTF-8：普通参数
• multipart/form-data; boundary=----WebKitFormBoundaryLKw1nLEcfWdwlRYH：上传文件，边界值boundary可以自定义

写入普通参数示例：

public static String doPost(String url, String params) {OutputStream out = null;BufferedReader in = null;try {URL realUrl = new URL(url);// 打开和URL之间的连接HttpURLConnection conn = (HttpURLConnection) realUrl.openConnection();// 设置请求参数conn.setRequestMethod("POST");conn.setConnectTimeout(5000);conn.setUseCaches(false);conn.setDoInput(true);// true：从URL连接读取数据，默认值为true，可以不填conn.setDoOutput(true);// true：数据写入URL连接，默认值false// 设置请求属性conn.setRequestProperty("accept", "*/*");conn.setRequestProperty("connection", "Keep-Alive");conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");// 设置请求体out = conn.getOutputStream();out.write(params.getBytes());out.flush();// 建立实际的连接conn.connect();// 获取所有响应头Map<String, List<String>> map = conn.getHeaderFields();for (String key : map.keySet()) {System.out.println(key + "=" + map.get(key));}// 获取响应String line = null;StringBuffer sb = new StringBuffer();in = new BufferedReader(new InputStreamReader(conn.getInputStream()));while ((line = in.readLine()) != null) {sb.append(line);}return sb.toString();} catch (Exception e) {e.printStackTrace();} finally {try {if (out != null) {out.close();}if (in != null) {in.close();in = null;}} catch (Exception e) {e.printStackTrace();}}return null;}

3.上传文件示例：

模拟表单上传文件，Content-Type设置为multipart/form-data，即模拟设置表单的enctype属性；其他属性参数参照浏览器发送的请求填写，如边界、传递的属性等。

/** * 模拟表单上传文件 * @param urlStr 请求的URL * @param file 文件 * @return 远程资源的响应结果 */public static String doUpload(String urlStr, File file) {OutputStream out = null;BufferedReader bufr = null;String result = "";try {URL url = new URL(urlStr);// 打开和URL之间的连接HttpURLConnection conn = (HttpURLConnection) url.openConnection();// 设置请求参数conn.setDoInput(true);conn.setDoOutput(true);conn.setUseCaches(false);conn.setRequestMethod("POST");// 设置请求属性conn.setRequestProperty("Accept", "*/*");conn.setRequestProperty("Connection", "Keep-Alive");// 定义边界String boundary = "----" + System.currentTimeMillis();conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);// 获取输出流out = conn.getOutputStream();// 请求体// 1.普通表单StringBuilder sb = new StringBuilder();sb.append("--").append(boundary).append("\r\n");// 必须多两道-sb.append("Content-Disposition: form-data; name=\"name1\"\r\n\r\n");sb.append("value1\r\n");out.write(sb.toString().getBytes("UTF-8"));// 2.sb = new StringBuilder();sb.append("--").append(boundary).append("\r\n");// 必须多两道-sb.append("Content-Disposition: form-data; name=\"name2\"\r\n\r\n");sb.append("value2\r\n");out.write(sb.toString().getBytes("UTF-8"));// 3.文件sb = new StringBuilder();sb.append("--").append(boundary).append("\r\n");// 必须多两道-sb.append("Content-Disposition: form-data; name=\"upload\"; filename=\"" + file.getName() + "\"\r\n");sb.append("Content-Type: application/octet-stream\r\n\r\n");out.write(sb.toString().getBytes("UTF-8"));// 写入文件BufferedInputStream bufin = new BufferedInputStream(new FileInputStream(file));int len = 0;byte[] bytes = new byte[1024];while ((len = bufin.read(bytes)) != -1) {out.write(bytes, 0, len);}bufin.close();// 结尾边界String foot = "\r\n\r\n--" + boundary + "--\r\n";out.write(foot.getBytes("UTF-8"));out.flush();// 读取响应bufr = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));String line;while ((line = bufr.readLine()) != null) {result += line;}conn.disconnect();} catch (Exception e) {e.printStackTrace();} finally {try {if (out != null) {out.close();}if (bufr != null) {bufr.close();}} catch (Exception e) {e.printStackTrace();}}return result;}

浏览器发送的请求：