Content-Type不同，写法也不同

HttpClient.java

import com.alibaba.fastjson.JSONObject;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpMethod;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.http.*;

public class HttpClient{
   /**
     * 发送application/json的post请求
     * @param url 支持https
     * @param headers
     * @param params
     * @param charset UTF-8
     * @return
     * @throws UnsupportedEncodingException
     */
    public static String post(String url, Map<String, String> headers, Map<String, String> params,String charset) throws UnsupportedEncodingException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
        HttpPost httpPost = new HttpPost(url);
        if (null != headers && headers.size() > 0) {
            for(String key : headers.keySet())
                httpPost.addHeader(key,headers.get(key));
        }
        if (null != params && params.size() > 0) {
            JSONObject jsonParam = new JSONObject();
            for (String key : params.keySet()) {
                jsonParam.put(key, params.get(key));
            }
            StringEntity entity = new StringEntity(jsonParam.toString(), charset);
            entity.setContentEncoding(charset);
            entity.setContentType("application/json;charset=utf-8");
            RequestConfig config = RequestConfig.custom().setSocketTimeout(5000).setConnectTimeout(5000).setConnectionRequestTimeout(5000).build();
            httpPost.setConfig(config);
            httpPost.setEntity(entity);
        }
        return executeRequest(httpPost, charset);
    }
     /**
     * 发送/x-www-form-urlencoded或者form-data的post请求
     * @param url 支持https
     * @param headers
     * @param params
     * @param charset UTF-8
     * @return
     * @throws UnsupportedEncodingException
     */
    public static String post2(String url, Map<String, String> headers, Map<String, String> params,String charset) throws UnsupportedEncodingException, NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
        HttpPost httpPost = new HttpPost(url);
        httpPost.addHeader("connection", "Keep-Alive");
        httpPost.addHeader("Content-Type", "application/x-www-form-urlencoded");
        if (null != headers && headers.size() > 0) {
            for(String key : headers.keySet())
                httpPost.addHeader(key,headers.get(key));
        }
        if (null != params && params.size() > 0) {
            List<NameValuePair> nvps = new ArrayList<>();
            for (String key : params.keySet()) {
                nvps.add(new BasicNameValuePair(key,params.get(key)));
            }
            UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(nvps, charset);
            formEntity.setContentEncoding(charset);
            RequestConfig config = RequestConfig.custom().setSocketTimeout(5000).setConnectTimeout(5000).setConnectionRequestTimeout(5000).build();
            httpPost.setConfig(config);
            httpPost.setEntity(formEntity);
        }
        return executeRequest(httpPost, charset);
    }

    /**
     * 执行一个http请求，传递HttpGet或HttpPost参数
     */
    public static String executeRequest(HttpUriRequest httpRequest, String charset) throws NoSuchAlgorithmException, KeyStoreException, KeyManagementException {
        CloseableHttpClient httpclient;
        if ("https".equals(httpRequest.getURI().getScheme())){
            httpclient = createSSLInsecureClient();
        }else{
            httpclient = HttpClients.createDefault();
        }
        String result = "";
        try {
            try {
                CloseableHttpResponse response = httpclient.execute(httpRequest);
                HttpEntity entity = null;
                try {
                    entity = response.getEntity();
                    result = EntityUtils.toString(entity, charset);
                } finally {
                    EntityUtils.consume(entity);
                    response.close();
                }
            } finally {
                httpclient.close();
            }
        }catch(IOException ex){
            ex.printStackTrace();
        }
        return result;
    }

    /**
     * 创建 SSL连接
     */
    public static CloseableHttpClient createSSLInsecureClient() throws KeyStoreException, NoSuchAlgorithmException, KeyManagementException {
        SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(new TrustStrategy() {
            @Override
            public boolean isTrusted(X509Certificate[] chain, String authType) throws CertificateException {
                return true;
            }
        }).build();
        SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslContext, new HostnameVerifier() {
            @Override
            public boolean verify(String hostname, SSLSession session) {
                return true;
            }
        });
        return HttpClients.custom().setSSLSocketFactory(sslsf).build();
    }
  
  
}

以上使用的是HttpClient 4.5.3，4.5以下版本设置超时方法与此不同。