一、介绍
最近在工作中需要在后台调用各种上传、下载、以及第三方服务接口，经过研究决定使用 HttpClient，自己封装了一个 HttpClient 工具类，简单轻松的实现get、post、put、delete 以及上传、下载请求，在此分享给大家。
二、实践应用
本文基于 HttpClient4.5.5 版本进行开发，也是现在最新的版本，之所以要提供版本说明，是因为 HttpClient 3 版本和 HttpClient 4 版本 API 差别还是很多大的，你把 HttpClient 3 版本的代码拿到 HttpClient 4 上面运行不起来，会报错的。所以在使用之前，一定要注意 HtppClient 的版本问题。
话不多说，直接上代码！
2.1、引用 HttpClient 依赖包
<dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.6</version> </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpcore</artifactId> <version>4.4.10</version> </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpmime</artifactId> <version>4.5.6</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.68</version> </dependency>
2.2、编写工具类（重点）
本次采用单利模式来初始化客户端，并用线程池来管理，同时支持http和https协议，项目启动之后，无需手动关闭httpClient客户端！
public class HttpUtils { private static final Logger log = LoggerFactory.getLogger(HttpUtils.class); private HttpUtils() {} //多线程共享实例 private static CloseableHttpClient httpClient; static { SSLContext sslContext = createSSLContext(); SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslContext, NoopHostnameVerifier.INSTANCE); // 注册http套接字工厂和https套接字工厂 Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory> create() .register("http", PlainConnectionSocketFactory.INSTANCE) .register("https", sslsf) .build(); // 连接池管理器 PoolingHttpClientConnectionManager connMgr = new PoolingHttpClientConnectionManager(socketFactoryRegistry); connMgr.setMaxTotal(300);//连接池最大连接数 connMgr.setDefaultMaxPerRoute(300);//每个路由最大连接数，设置的过小，无法支持大并发 connMgr.setValidateAfterInactivity(5 * 1000); //在从连接池获取连接时，连接不活跃多长时间后需要进行一次验证 // 请求参数配置管理器 RequestConfig requestConfig = RequestConfig.custom() .setConnectTimeout(60000) .setSocketTimeout(60000) .setConnectionRequestTimeout(60000) .build(); // 获取httpClient客户端 httpClient = HttpClients.custom() .setConnectionManager(connMgr) .setDefaultRequestConfig(requestConfig) .build(); } /** * GET请求 * @param url * @return */ public static String getUrl(String url) { return sendHttp(HttpMethod.GET, url, null, null); } /** * GET请求/带头部的信息 * @param url * @param header * @return */ public static String getUrl(String url, Map<String, String> header) { return sendHttp(HttpMethod.GET, url, header, null); } /** * POST请求/无参数 * @param url * @return */ public static String postJson(String url) { return postJson(url, null, null); } /** * POST请求/有参数 * @param url * @param param * @return */ public static String postJson(String url, String param) { return postJson(url, null, param); } /** * POST请求/无参数带头部 * @param url * @param header * @return */ public static String postJson(String url, Map<String, String> header) { return postJson(url, header, null); } /** * POST请求/有参数带头部 * @param url * @param header * @param params * @return */ public static String postJson(String url, Map<String, String> header, String params) { return sendHttp(HttpMethod.POST, url, header, params); } /** * 上传文件流 * @param url * @param header * @param param * @param fileName * @param inputStream * @return */ public static RequestResult postUploadFileStream(String url, Map<String, String> header, Map<String, String> param, String fileName, InputStream inputStream) { byte[] stream = inputStream2byte(inputStream); return postUploadFileStream(url, header, param, fileName, stream); } /** * 上传文件 * @param url 上传地址 * @param header 请求头部 * @param param 请求表单 * @param fileName 文件名称 * @param stream 文件流 * @return */ public static RequestResult postUploadFileStream(String url, Map<String, String> header, Map<String, String> param, String fileName, byte[] stream) { String infoMessage = new StringBuilder().append("request postUploadFileStream，url:").append(url).append("，header:").append(header.toString()).append("，param:").append(JSONObject.toJSONString(param)).append("，fileName:").append(fileName).toString(); log.info(infoMessage); RequestResult result = new RequestResult(); if(StringUtils.isBlank(fileName)){ log.warn("上传文件名称为空"); throw new RuntimeException("上传文件名称为空"); } if(Objects.isNull(stream)){ log.warn("上传文件流为空"); throw new RuntimeException("上传文件流为空"); } try { ContentType contentType = ContentType.MULTIPART_FORM_DATA.withCharset("UTF-8"); HttpPost httpPost = new HttpPost(url); if (Objects.nonNull(header) && !header.isEmpty()) { for (Map.Entry<String, String> entry : header.entrySet()) { httpPost.setHeader(entry.getKey(), entry.getValue()); if(log.isDebugEnabled()){ log.debug(entry.getKey() + ":" + entry.getValue()); } } } MultipartEntityBuilder builder = MultipartEntityBuilder.create(); builder.setCharset(Charset.forName("UTF-8"));//使用UTF-8 builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);//设置浏览器兼容模式 if (Objects.nonNull(param) && !param.isEmpty()) { for (Map.Entry<String, String> entry : param.entrySet()) { if (log.isDebugEnabled()) { log.debug(entry.getKey() + ":" + entry.getValue()); } builder.addPart(entry.getKey(), new StringBody(entry.getValue(), contentType)); } } builder.addBinaryBody("file", stream, contentType, fileName);//封装上传文件 httpPost.setEntity(builder.build()); //请求执行，获取返回对象 CloseableHttpResponse response = httpClient.execute(httpPost); log.info("postUploadFileStream response status:{}", response.getStatusLine()); int statusCode = response.getStatusLine().getStatusCode(); if (statusCode == HttpStatus.SC_OK || statusCode == HttpStatus.SC_NO_CONTENT) { result.setSuccess(true); } HttpEntity httpEntity = response.getEntity(); if (Objects.nonNull(httpEntity)) { String content = EntityUtils.toString(httpEntity, "UTF-8"); log.info("postUploadFileStream response body:{}", content); result.setMsg(content); } HttpClientUtils.closeQuietly(response); } catch (Exception e) { log.error(infoMessage + " failure", e); result.setMsg("请求异常"); } return result; } /** * 从下载地址获取文件流(如果链接出现双斜杠，请用OKHttp) * @param url * @return */ public static ByteArrayOutputStream getDownloadFileStream(String url) { String infoMessage = new StringBuilder().append("request getDownloadFileStream，url:").append(url).toString(); log.info(infoMessage); ByteArrayOutputStream byteOutStream = null; try { CloseableHttpResponse response = httpClient.execute(new HttpGet(url)); log.info("getDownloadFileStream response status:{}", response.getStatusLine()); int statusCode = response.getStatusLine().getStatusCode(); if (statusCode == HttpStatus.SC_OK) { //请求成功 HttpEntity entity = response.getEntity(); if (entity != null && entity.getContent() != null) { //复制输入流 byteOutStream = cloneInputStream(entity.getContent()); } } HttpClientUtils.closeQuietly(response); } catch (Exception e) { log.error(infoMessage + " failure", e); } return byteOutStream; } /** * 发送http请求(通用方法) * @param httpMethod 请求方式（GET、POST、PUT、DELETE） * @param url 请求路径 * @param header 请求头 * @param params 请求body（json数据） * @return 响应文本 */ public static String sendHttp(HttpMethod httpMethod, String url, Map<String, String> header, String params) { String infoMessage = new StringBuilder().append("request sendHttp，url:").append(url).append("，method:").append(httpMethod.name()).append("，header:").append(JSONObject.toJSONString(header)).append("，param:").append(params).toString(); log.info(infoMessage); //返回结果 String result = null; long beginTime = System.currentTimeMillis(); try { ContentType contentType = ContentType.APPLICATION_JSON.withCharset("UTF-8"); HttpRequestBase request = buildHttpMethod(httpMethod, url); if (Objects.nonNull(header) && !header.isEmpty()) { for (Map.Entry<String, String> entry : header.entrySet()) { //打印头部信息 if(log.isDebugEnabled()){ log.debug(entry.getKey() + ":" + entry.getValue()); } request.setHeader(entry.getKey(), entry.getValue()); } } if (StringUtils.isNotEmpty(params)) { if(HttpMethod.POST.equals(httpMethod) || HttpMethod.PUT.equals(httpMethod)){ ((HttpEntityEnclosingRequest) request).setEntity(new StringEntity(params, contentType)); } } CloseableHttpResponse response = httpClient.execute(request); HttpEntity httpEntity = response.getEntity(); log.info("sendHttp response status:{}", response.getStatusLine()); if (Objects.nonNull(httpEntity)) { result = EntityUtils.toString(httpEntity, "UTF-8"); log.info("sendHttp response body:{}", result); } HttpClientUtils.closeQuietly(response);//关闭返回对象 } catch (Exception e) { log.error(infoMessage + " failure", e); } long endTime = System.currentTimeMillis(); log.info("request sendHttp response time cost:" + (endTime - beginTime) + " ms"); return result; } /** * 请求方法（全大些） */ public enum HttpMethod { GET, POST, PUT, DELETE } /** * 上传返回结果封装 */ public static class RequestResult{ private boolean isSuccess;//是否成功 private String msg;//消息 public boolean isSuccess() { return isSuccess; } public RequestResult setSuccess(boolean success) { isSuccess = success; return this; } public String getMsg() { return msg; } public RequestResult setMsg(String msg) { this.msg = msg; return this; } public RequestResult() { this.isSuccess = false; } } /** * 构建请求方法 * @param method * @param url * @return */ private static HttpRequestBase buildHttpMethod(HttpMethod method, String url) { if (HttpMethod.GET.equals(method)) { return new HttpGet(url); } else if (HttpMethod.POST.equals(method)) { return new HttpPost(url); } else if (HttpMethod.PUT.equals(method)) { return new HttpPut(url); } else if (HttpMethod.DELETE.equals(method)) { return new HttpDelete(url); } else { return null; } } /** * 配置证书 * @return */ private static SSLContext createSSLContext(){ try { //信任所有,支持导入ssl证书 TrustStrategy acceptingTrustStrategy = (cert, authType) -> true; SSLContext sslContext = SSLContexts.custom().loadTrustMaterial(null, acceptingTrustStrategy).build(); return sslContext; } catch (Exception e) { log.error("初始化ssl配置失败", e); throw new RuntimeException("初始化ssl配置失败"); } } /** * 复制文件流 * @param input * @return */ private static ByteArrayOutputStream cloneInputStream(InputStream input) { try { ByteArrayOutputStream byteOutStream = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len; while ((len = input.read(buffer)) > -1) { byteOutStream.write(buffer, 0, len); } byteOutStream.flush(); return byteOutStream; } catch (IOException e) { log.warn("copy InputStream error，{}", ExceptionUtils.getStackTrace(e)); } return null; } /** * 输入流转字节流 * @param in * @return */ private static byte[] inputStream2byte(InputStream in) { ByteArrayOutputStream bos = null; try { bos = new ByteArrayOutputStream(); byte[] b = new byte[1024]; int n; while ((n = in.read(b)) != -1) { bos.write(b, 0, n); } in.close(); bos.close(); byte[] buffer = bos.toByteArray(); return buffer; } catch (IOException e) { log.warn("inputStream transfer byte error，{}", ExceptionUtils.getStackTrace(e)); } finally { try { if (in != null) { in.close(); } } catch (IOException e) { log.error("clone inputStream error", e); } try { if (bos != null) { bos.close(); } } catch (IOException e) { log.error("clone outputStream error", e); } } return null; } }
除了上传、下载请求之外，默认封装的请求参数格式都是application/json，如果不够，可以根据自己的业务场景进行封装处理！
其中sendHttp是一个支持GET、POST、PUT、DELETE请求的通用方法，上面介绍的getUrl、postJosn等方法，最终都会调用到这个方法！
2.3、接口请求示例
工具包封装完成之后，在代码中使用起来也非常简单，直接采用工具类方法就可以直接使用，例如下面以post方式请求某个接口！
public static void main(String[] args) throws Exception { String url = "https://101.231.204.80:5000/gateway/api/queryTrans.do"; String result= HttpUtils.postJson(url); System.out.println(result); }
三、小结
在编写工具类的时候，需要注意的地方是，尽可能保证httpClient客户端全局唯一，也就是采用单利模式，如果我们每次请求都初始化一个客户端，结束之后又将其关闭，在高并发的接口请求场景下，性能效率急剧下降！
HttpClients客户端的初始化参数配置非常丰富，本文默认初始化的线程池为300，在实际的业务开发中，大家还可以结合自己的业务场景进行调优，具体的配置可以参考官网文档，地址：Apache HttpComponents
