什么是httpclient
HTTP 协议可能是现在 Internet 上使用得最多、最重要的协议了，越来越多的 Java 应用程序需要直接通过 HTTP 协议来访问网络资源。虽然在 JDK 的 java net包中已经提供了访问 HTTP 协议的基本功能，但是对于大部分应用程序来说，JDK 库本身提供的功能还不够丰富和灵活。HttpClient 是 Apache Jakarta Common 下的子项目，用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包，并且它支持 HTTP 协议最新的版本和建议。
下载地址：
http://hc.apache.org/
2.
功能介绍
以下列出的是 HttpClient 提供的主要的功能，要知道更多详细的功能可以参见 HttpClient 的主页。
（1）实现了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）
（2）支持自动转向
（3）支持 HTTPS 协议
（4）支持代理服务器等
导入依赖
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient --><dependency> ???<groupId>org.apache.httpcomponents</groupId> ???<artifactId>httpclient</artifactId> ???<version>4.3.5</version></dependency>
执行GET请求
public class DoGET { ???public static void main(String[] args) throws Exception { ???????// 创建Httpclient对象 ???????CloseableHttpClient httpclient = HttpClients.createDefault(); ???????// 创建http GET请求 ???????HttpGet httpGet = new HttpGet("http://www.baidu.com/"); ???????CloseableHttpResponse response = null; ???????try { ???????????// 执行请求 ???????????response = httpclient.execute(httpGet); ???????????// 判断返回状态是否为200 ???????????if (response.getStatusLine().getStatusCode() == 200) { ???????????????String content = EntityUtils.toString(response.getEntity(), "UTF-8"); ???????????????System.out.println("内容长度：" + content.length());// ???????????????FileUtils.writeStringToFile(new File("C:\\baidu.html"), content); ???????????} ???????} finally { ???????????if (response != null) { ???????????????response.close(); ???????????} ???????????httpclient.close(); ???????} ???}}执行GET带参数
public class DoGETParam { ???public static void main(String[] args) throws Exception { ???????// 创建Httpclient对象 ???????CloseableHttpClient httpclient = HttpClients.createDefault(); ???????// 定义请求的参数 ???????URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "java").build(); ???????System.out.println(uri); ???????// 创建http GET请求 ???????HttpGet httpGet = new HttpGet(uri); ???????CloseableHttpResponse response = null; ???????try { ???????????// 执行请求 ???????????response = httpclient.execute(httpGet); ???????????// 判断返回状态是否为200 ???????????if (response.getStatusLine().getStatusCode() == 200) { ???????????????String content = EntityUtils.toString(response.getEntity(), "UTF-8"); ???????????????System.out.println(content); ???????????} ???????} finally { ???????????if (response != null) { ???????????????response.close(); ???????????} ???????????httpclient.close(); ???????} ???}}执行post请求
public class DoPOST { ???public static void main(String[] args) throws Exception { ???????// 创建Httpclient对象 ???????CloseableHttpClient httpclient = HttpClients.createDefault(); ???????// 创建http POST请求 ???????HttpPost httpPost = new HttpPost("http://www.oschina.net/"); ???????CloseableHttpResponse response = null; ???????try { ???????????// 执行请求 ???????????response = httpclient.execute(httpPost); ???????????// 判断返回状态是否为200 ???????????if (response.getStatusLine().getStatusCode() == 200) { ???????????????String content = EntityUtils.toString(response.getEntity(), "UTF-8"); ???????????????System.out.println(content); ???????????} ???????} finally { ???????????if (response != null) { ???????????????response.close(); ???????????} ???????????httpclient.close(); ???????} ???}}带参数的post请求
public class DoPOSTParam { ???public static void main(String[] args) throws Exception { ???????// 创建Httpclient对象 ???????CloseableHttpClient httpclient = HttpClients.createDefault(); ???????// 创建http POST请求 ???????HttpPost httpPost = new HttpPost("http://www.oschina.net/search"); ???????// 设置2个post参数，一个是scope、一个是q ???????List<NameValuePair> parameters = new ArrayList<NameValuePair>(0); ???????parameters.add(new BasicNameValuePair("scope", "project")); ???????parameters.add(new BasicNameValuePair("q", "java")); ???????// 构造一个form表单式的实体 ???????UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters); ???????// 将请求实体设置到httpPost对象中 ???????httpPost.setEntity(formEntity); ???????CloseableHttpResponse response = null; ???????try { ???????????// 执行请求 ???????????response = httpclient.execute(httpPost); ???????????// 判断返回状态是否为200 ???????????if (response.getStatusLine().getStatusCode() == 200) { ???????????????String content = EntityUtils.toString(response.getEntity(), "UTF-8"); ???????????????System.out.println(content); ???????????} ???????} finally { ???????????if (response != null) { ???????????????response.close(); ???????????} ???????????httpclient.close(); ???????} ???}}封装HttpClient通用工具类
public class HttpClientUtil { ???public static String doGet(String url, Map<String, String> param) { ???????// 创建Httpclient对象 ???????CloseableHttpClient httpclient = HttpClients.createDefault(); ???????String resultString = ""; ???????CloseableHttpResponse response = null; ???????try { ???????????// 创建uri ???????????URIBuilder builder = new URIBuilder(url); ???????????if (param != null) { ???????????????for (String key : param.keySet()) { ???????????????????builder.addParameter(key, param.get(key)); ???????????????} ???????????} ???????????URI uri = builder.build(); ???????????// 创建http GET请求 ???????????HttpGet httpGet = new HttpGet(uri); ???????????// 执行请求 ???????????response = httpclient.execute(httpGet); ???????????// 判断返回状态是否为200 ???????????if (response.getStatusLine().getStatusCode() == 200) { ???????????????resultString = EntityUtils.toString(response.getEntity(), "UTF-8"); ???????????} ???????} catch (Exception e) { ???????????e.printStackTrace(); ???????} finally { ???????????try { ???????????????if (response != null) { ???????????????????response.close(); ???????????????} ???????????????httpclient.close(); ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????} ???????return resultString; ???} ???public static String doGet(String url) { ???????return doGet(url, null); ???} ???public static String doPost(String url, Map<String, String> param) { ???????// 创建Httpclient对象 ???????CloseableHttpClient httpClient = HttpClients.createDefault(); ???????CloseableHttpResponse response = null; ???????String resultString = ""; ???????try { ???????????// 创建Http Post请求 ???????????HttpPost httpPost = new HttpPost(url); ???????????// 创建参数列表 ???????????if (param != null) { ???????????????List<NameValuePair> paramList = new ArrayList<>(); ???????????????for (String key : param.keySet()) { ???????????????????paramList.add(new BasicNameValuePair(key, param.get(key))); ???????????????} ???????????????// 模拟表单 ???????????????UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList); ???????????????httpPost.setEntity(entity); ???????????} ???????????// 执行http请求 ???????????response = httpClient.execute(httpPost); ???????????resultString = EntityUtils.toString(response.getEntity(), "utf-8"); ???????} catch (Exception e) { ???????????e.printStackTrace(); ???????} finally { ???????????try { ???????????????response.close(); ???????????} catch (IOException e) { ???????????????// TODO Auto-generated catch block ???????????????e.printStackTrace(); ???????????} ???????} ???????return resultString; ???} ???public static String doPost(String url) { ???????return doPost(url, null); ???}}
httpclient
原文地址：https://www.cnblogs.com/inspred/p/9521098.html