maven：

<dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.2</version>
        </dependency>

java

/**
 * @author QY
 * @date 2017年10月23日 下午2:49
 * HttpClient工具类
 */
public class HttpUtil {

    //private static Logger logger = Logger.getLogger(HttpUtil.class);

    /**
     * get请求
     * @return
     */
    public static String doGet(String url) {
        try {
            HttpClient client = new DefaultHttpClient();
            //发送get请求
            HttpGet request = new HttpGet(url);
            HttpResponse response = client.execute(request);

            /**请求发送成功，并得到响应**/
            if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                /**读取服务器返回过来的json字符串数据**/
                String strResult = EntityUtils.toString(response.getEntity());

                return strResult;
            }
        }
        catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }

    /**
     * post请求(用于key-value格式的参数)
     * @param url
     * @param params
     * @return
     */
    public static String doPost(String url, Map params){

        BufferedReader in = null;
        try {
            // 定义HttpClient  
            HttpClient client = new DefaultHttpClient();
            // 实例化HTTP方法  
            HttpPost request = new HttpPost();
            request.setURI(new URI(url));

            //设置参数
            List<NameValuePair> nvps = new ArrayList<NameValuePair>();
            for (Iterator iter = params.keySet().iterator(); iter.hasNext();) {
                String name = (String) iter.next();
                String value = String.valueOf(params.get(name));
                nvps.add(new BasicNameValuePair(name, value));

                //System.out.println(name +"-"+value);
            }
            request.setEntity(new UrlEncodedFormEntity(nvps,HTTP.UTF_8));

            HttpResponse response = client.execute(request);
            int code = response.getStatusLine().getStatusCode();
            if(code == 200){    //请求成功
                in = new BufferedReader(new InputStreamReader(response.getEntity()
                        .getContent(),"utf-8"));
                StringBuffer sb = new StringBuffer("");
                String line = "";
                String NL = System.getProperty("line.separator");
                while ((line = in.readLine()) != null) {
                    sb.append(line + NL);
                }

                in.close();

                return sb.toString();
            }
            else{    //
                System.out.println("状态码：" + code);
                return null;
            }
        }
        catch(Exception e){
            e.printStackTrace();

            return null;
        }
    }

    /**
     * post请求（用于请求json格式的参数）
     * @param url
     * @param params
     * @return
     */
    public static String doPost(String url, String params) throws Exception {

        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost(url);// 创建httpPost   
        httpPost.setHeader("Accept", "application/json");
        httpPost.setHeader("Content-Type", "application/json");
        String charSet = "UTF-8";
        StringEntity entity = new StringEntity(params, charSet);
        httpPost.setEntity(entity);
        CloseableHttpResponse response = null;

        try {

            response = httpclient.execute(httpPost);
            StatusLine status = response.getStatusLine();
            int state = status.getStatusCode();
            if (state == HttpStatus.SC_OK) {
                HttpEntity responseEntity = response.getEntity();
                String jsonString = EntityUtils.toString(responseEntity);
                return jsonString;
            }
            else{
                //logger.error("请求返回:"+state+"("+url+")");
            }
        }
        finally {
            if (response != null) {
                try {
                    response.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            try {
                httpclient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }
/** * post请求（用于请求xml格式的参数）
 * @param url
 * @param params
 * @return
 */
public static String doPostXml(String url, String xml){

    BufferedReader in = null;
    try {
        // 定义HttpClient

        HttpClient client = HttpClientBuilder.create().build();
        // 实例化HTTP方法
        HttpPost request = new HttpPost();
        request.setURI(new URI(url));


        request.setEntity(new StringEntity(xml));

        HttpResponse response = client.execute(request);
        int code = response.getStatusLine().getStatusCode();
        if(code == 200){    //请求成功
            in = new BufferedReader(new InputStreamReader(response.getEntity()
                    .getContent(),"utf-8"));
            StringBuffer sb = new StringBuffer("");
            String line = "";
            String NL = System.getProperty("line.separator");
            while ((line = in.readLine()) != null) {
                sb.append(line + NL);
            }

            in.close();

            return sb.toString();
        }
        else{    //
            System.out.println("状态码：" + code);
            return null;
        }
    }
    catch(Exception e){
        e.printStackTrace();

        return null;
    }
}
}