最近调用外部厂商提供的Post接口，总结了几种方法：

一、项目的maven依赖：

		<dependency>
			<groupId>org.apache.httpcomponents</groupId>
			<artifactId>httpcore</artifactId>
			<version>4.4.5</version>
		</dependency>
		<dependency>
			<groupId>org.apache.httpcomponents</groupId>
			<artifactId>httpclient</artifactId>
			<version>4.5.6</version>
		</dependency>
		<dependency>
			<groupId>org.apache.httpcomponents</groupId>
			<artifactId>httpmime</artifactId>
			<version>4.5.2</version>
		</dependency>
		<!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
		<dependency>
			<groupId>com.google.guava</groupId>
			<artifactId>guava</artifactId>
			<version>27.0.1-jre</version>
		</dependency>
		<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>1.7.25</version>
		</dependency>
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>fastjson</artifactId>
			<version>1.2.28</version>
		</dependency>

二.post请求代码：

1.含上传图片（非JSON）：

    public static String requestOCRForHttp(String url, Map<String, String> requestParams, String filePathAndName)
            throws Exception {
        String result = null;
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //设置超时时间
        RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(5000).setConnectionRequestTimeout(1000).setSocketTimeout(5000).build();
        /** HttpPost */
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(requestConfig);
        MultipartEntity reqEntity = new MultipartEntity(); // 建立多文件实例
        FileBody filebody = new FileBody(new File(filePathAndName));
        reqEntity.addPart("pic", filebody);// upload为请求后台的File upload;
        for (String key : requestParams.keySet()) {
            String value = requestParams.get(key);
            reqEntity.addPart(key, new StringBody(value, Charset.forName("utf-8")));
        }
        httpPost.setEntity(reqEntity); // 设置实体
        /** HttpResponse */
        CloseableHttpResponse httpResponse = httpClient.execute(httpPost);
        try {
            HttpEntity httpEntity = httpResponse.getEntity();
            result = EntityUtils.toString(httpEntity, "utf-8");
            EntityUtils.consume(httpEntity);
        } finally {
            try {
                if (httpResponse != null) {
                    httpResponse.close();
                }
            } catch (IOException e) {
                logger.info("## release resouce error ##" + e);
            }
        }
        return result;
    }

2.post的String参数（非JSON）

	public static String requestOCRForHttp(String url, Map<String, String> requestParams) throws Exception {
        String result = null;
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //设置超时时间
        RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(5000).setConnectionRequestTimeout(1000).setSocketTimeout(5000).build();
        /** HttpPost */
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(requestConfig);
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        Iterator<Entry<String, String>> it = requestParams.entrySet().iterator();
//		System.out.println(params.toString());
        while (it.hasNext()) {
            Entry<String, String> en = it.next();
            String key = en.getKey();
            String value = en.getValue();
            if (value != null) {
                params.add(new BasicNameValuePair(key, value));
            }
        }
        httpPost.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));
        /** HttpResponse */
        CloseableHttpResponse httpResponse = httpClient.execute(httpPost);
        try {
            HttpEntity httpEntity = httpResponse.getEntity();
            result = EntityUtils.toString(httpEntity, "utf-8");
            EntityUtils.consume(httpEntity);
        } finally {
            try {
                if (httpResponse != null) {
                    httpResponse.close();
                }
            } catch (IOException e) {
                logger.info("## release resouce error ##" + e);
            }
        }
        return result;
    }

3.POST请求（JSON）：

	public static String sendHttpPost(String url, String JSONBody) throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //设置超时时间
        RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(5000).setConnectionRequestTimeout(1000).setSocketTimeout(5000).build();
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(requestConfig);
        httpPost.addHeader("Content-Type", "application/json");
        httpPost.setEntity(new StringEntity(JSONBody));
        CloseableHttpResponse response = httpClient.execute(httpPost);
//		System.out.println(response.getStatusLine().getStatusCode() + "\n");
        HttpEntity entity = response.getEntity();
        String responseContent = EntityUtils.toString(entity, "UTF-8");
//		System.out.println(responseContent);
        response.close();
        httpClient.close();
        return responseContent;
    }