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();
}
}