Java开源简单实用的Http工具类

/**
 * @file HttpUtil.java
 * 
 * @brief 
 * HttpUtil is a single class containing methods to conveniently perform HTTP 
 * requests. HttpUtil only uses regular java io and net functionality and does 
 * not depend on external libraries. 
 * The class contains methods to perform a get, post, put, and delete request,
 * and supports posting forms. Optionally, one can provide headers.
 *
 * Example usage:
 * 
 *     // get
 *     String res = HttpUtil.get("http://www.google.com");
 * 
 *     // post
 *     String res = HttpUtil.post("http://sendmedata.com", "This is the data");
 *
 *     // post form
 *     Map<String, String> params = new HashMap<String, String>();
 *     params.put("firstname", "Joe");
 *     params.put("lastname", "Smith");
 *     params.put("age", "28");
 *     String res = HttpUtil.postForm("http://site.com/newuser", params);
 *
 *     // append query parameters to url
 *     String url = "http://mydatabase.com/users";
 *     Map<String, String> params = new HashMap<String, String>();
 *     params.put("orderby", "name");
 *     params.put("limit", "10");
 *     String fullUrl = HttpUtil.appendQueryParams(url, params);
 *     // fullUrl = "http://mydatabase.com/user?orderby=name&limit=10"
 *
 * @license
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy 
 * of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 *
 * Copyright (c) 2012 Almende B.V.
 *
 * @author  Jos de Jong, <jos@almende.org>
 * @date      2012-05-14
 */
 
package com.almende.util;
 
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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 {
    /**
     * Send a get request
     * @param url
     * @return response
     * @throws IOException 
     */
    static public 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 
     */
    static public 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 
     */
    static public 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 
     */
    static public 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 
     */
    static public 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 
     */
    static public String postForm(String url, Map<String, String> params,
            Map<String, String> headers) throws IOException {
        // set content type
        if (headers == null) {
            headers = new HashMap<String, String>();
        }
        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 
     */
    static public 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 
     */
    static public 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 
     */
    static public 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 
     */
    static public 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 
     */
    static public String appendQueryParams(String url, 
            Map<String, String> params) throws IOException {
        String fullUrl = new String(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") + '=';
                fullUrl += 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 
     */
    static public Map<String, String> getQueryParams(String url) 
            throws IOException {
        Map<String, String> params = new HashMap<String, String>();
     
        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 
     */
    static public 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 
     */
    static public 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(10000);
        conn.setReadTimeout(10000);
 
        // 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
     */
    static public String streamToString(InputStream in) throws IOException {
        StringBuffer out = new StringBuffer();
        byte[] b = new byte[4096];
        for (int n; (n = in.read(b)) != -1;) {
            out.append(new String(b, 0, n));
        }
        return out.toString();
    }
}

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