方便发送 Http 请求，不需要引入第三方依赖。
import java.io.*; import java.net.HttpURLConnection; import java.net.URL; import java.net.URLDecoder; import java.net.URLEncoder; import java.util.HashMap; import java.util.Map; public class HttpUtil { public static void main(String[] args) throws IOException { Map<String, String> map = new HashMap<>(); map.put("Accept", "*/*"); map.put("Pragma", "no-cache"); map.put("Connection", "keep-alive"); map.put("Cache-Control", "no-cache"); map.put("Accept-Language", "zh-CN,zh;q=0.9"); // map.put("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.142 Safari/537.36"); String url = "http://www.baidu.com/"; String html = get(url, map); System.out.println(html); } /** * Send a get request * * @param url * @return response * @throws IOException */ public static String get(String url) throws IOException { return get(url, null); } /** * Send a get request * * @param url Url as string * @param headers Optional map with headers * @return response Response as string * @throws IOException */ public static String get(String url, Map<String, String> headers) throws IOException { return fetch("GET", url, null, headers); } /** * Send a post request * * @param url Url as string * @param body Request body as string * @param headers Optional map with headers * @return response Response as string * @throws IOException */ public static String post(String url, String body, Map<String, String> headers) throws IOException { return fetch("POST", url, body, headers); } /** * Send a post request * * @param url Url as string * @param body Request body as string * @return response Response as string * @throws IOException */ public static String post(String url, String body) throws IOException { return post(url, body, null); } /** * Post a form with parameters * * @param url Url as string * @param params map with parameters/values * @return response Response as string * @throws IOException */ public static String postForm(String url, Map<String, String> params) throws IOException { return postForm(url, params, null); } /** * Post a form with parameters * * @param url Url as string * @param params Map with parameters/values * @param headers Optional map with headers * @return response Response as string * @throws IOException */ public static String postForm(String url, Map<String, String> params, Map<String, String> headers) throws IOException { // set content type if (headers == null) { headers = new HashMap<>(); } headers.put("Content-Type", "application/x-www-form-urlencoded"); // parse parameters String body = ""; if (params != null) { boolean first = true; for (String param : params.keySet()) { if (first) { first = false; } else { body += "&"; } String value = params.get(param); body += URLEncoder.encode(param, "UTF-8") + "="; body += URLEncoder.encode(value, "UTF-8"); } } return post(url, body, headers); } /** * Send a put request * * @param url Url as string * @param body Request body as string * @param headers Optional map with headers * @return response Response as string * @throws IOException */ public static String put(String url, String body, Map<String, String> headers) throws IOException { return fetch("PUT", url, body, headers); } /** * Send a put request * * @param url Url as string * @return response Response as string * @throws IOException */ public static String put(String url, String body) throws IOException { return put(url, body, null); } /** * Send a delete request * * @param url Url as string * @param headers Optional map with headers * @return response Response as string * @throws IOException */ public static String delete(String url, Map<String, String> headers) throws IOException { return fetch("DELETE", url, null, headers); } /** * Send a delete request * * @param url Url as string * @return response Response as string * @throws IOException */ public static String delete(String url) throws IOException { return delete(url, null); } /** * Append query parameters to given url * * @param url Url as string * @param params Map with query parameters * @return url Url with query parameters appended * @throws IOException */ public static String appendQueryParams(String url, Map<String, String> params) throws IOException { String fullUrl = url; if (params != null) { boolean first = (fullUrl.indexOf('?') == -1); for (String param : params.keySet()) { if (first) { fullUrl += '?'; first = false; } else { fullUrl += '&'; } String value = params.get(param); fullUrl += URLEncoder.encode(param, "UTF-8") + '=' + URLEncoder.encode(value, "UTF-8"); } } return fullUrl; } /** * Retrieve the query parameters from given url * * @param url Url containing query parameters * @return params Map with query parameters * @throws IOException */ public static Map<String, String> getQueryParams(String url) throws IOException { Map<String, String> params = new HashMap<>(); int start = url.indexOf('?'); while (start != -1) { // read parameter name int equals = url.indexOf('=', start); String param = ""; if (equals != -1) { param = url.substring(start + 1, equals); } else { param = url.substring(start + 1); } // read parameter value String value = ""; if (equals != -1) { start = url.indexOf('&', equals); if (start != -1) { value = url.substring(equals + 1, start); } else { value = url.substring(equals + 1); } } params.put(URLDecoder.decode(param, "UTF-8"), URLDecoder.decode(value, "UTF-8")); } return params; } /** * Returns the url without query parameters * * @param url Url containing query parameters * @return url Url without query parameters * @throws IOException */ public static String removeQueryParams(String url) throws IOException { int q = url.indexOf('?'); if (q != -1) { return url.substring(0, q); } else { return url; } } /** * Send a request * * @param method HTTP method, for example "GET" or "POST" * @param url Url as string * @param body Request body as string * @param headers Optional map with headers * @return response Response as string * @throws IOException */ public static String fetch(String method, String url, String body, Map<String, String> headers) throws IOException { // connection URL u = new URL(url); HttpURLConnection conn = (HttpURLConnection) u.openConnection(); conn.setConnectTimeout(100000); conn.setReadTimeout(300000); // method if (method != null) { conn.setRequestMethod(method); } // headers if (headers != null) { for (String key : headers.keySet()) { conn.addRequestProperty(key, headers.get(key)); } } // body if (body != null) { conn.setDoOutput(true); OutputStream os = conn.getOutputStream(); os.write(body.getBytes()); os.flush(); os.close(); } // response InputStream is = conn.getInputStream(); String response = streamToString(is); is.close(); // handle redirects if (conn.getResponseCode() == 301) { String location = conn.getHeaderField("Location"); return fetch(method, location, body, headers); } return response; } /** * Read an input stream into a string * * @param in * @return * @throws IOException */ public static String streamToString(InputStream in) throws IOException { StringBuffer out = new StringBuffer(); BufferedReader br = new BufferedReader(new InputStreamReader(in, "UTF-8")); String line; while ((line = br.readLine()) != null) { out.append(line); } // byte[] b = new byte[4096]; // for (int n; (n = in.read(b)) != -1; ) { // out.append(new String(b, 0, n)); // } return out.toString(); } }