HttpClient 是Apache Jakarta Common 下的子项目，可以用来提供高效的、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。

就是用来发送http请求或者解析http响应的。

导入依赖：

<dependency><groupId>org.apache.httpcomponents</groupId><artifactId>httpclient</artifactId><version>4.5.13</version>
</dependency>

使用步骤：

1. 创建HttpClient实例

2. 创建某种连接方法的实例

3. 调用HttpClient实例的execute方法来执行请求方法

4. 读取response

5. 释放连接，无论执行方法是否成功

发送get请求：

• 创建HttpClient实例

CloseableHttpClient httpClient = HttpClients.createDefault();

• 创建GET请求方法实例

HttpGet httpGet = new HttpGet("http地址");

• 调用HttpClient实例执行GET实例，返回response

CloseableHttpResponse response = httpClient.execute(httpGet);

• 解析response

// 获取状态码
int status = response.getStatusLine().getStatusCode();
// 获取实例
HttpEntity entity = response.getEntity();
// 获取实例数据
String html = EntityUtils.toString(entity);

• 释放连接

response.close();
httpClient.close();

发送post请求：

与get请求方式基本相同，只需在创建POST请求实例后，使用实例对象调用setEntity(new StringEntity("参数"));设置参数

• 创建HttpClient实例

CloseableHttpClient httpClient = HttpClients.createDefault();

• 创建POST请求方法实例

HttpGet httpPost = new HttpPost("http地址");

• 设置参数

httpPost.setEntity(new StringEntity("参数"));

• 调用HttpClient实例执行GET实例，返回response

CloseableHttpResponse response = httpClient.execute(httpPost);

• 解析response

// 获取状态码
int status = response.getStatusLine().getStatusCode();
// 获取实例
HttpEntity entity = response.getEntity();
// 获取实例数据
String html = EntityUtils.toString(entity);

• 释放连接

response.close();
httpClient.close();

使用表单提交参数：

提交表单一共就这几步：

1. 创建http实例

2. 创建Post请求

3. 设置表单参数并让Post携带

4. 执行请求，获取响应

5. 解析响应

6. 关闭资源

// 1. 创建HttpClient实例
CloseableHttpClient httpClient = HttpClients.createDefault();
​
// 2. 设置表单参数
List<NameValuePair> listValues =  new ArrayList<>();
listValues.add(new BasicNameValuePair("name", "root"));
listValues.add(new BasicNameValuePair("password", "123456"));
​
// 3. 创建HttpPost实例
HttpPost httpPost = new HttpPost("http://httpbin.org/post");
​
// 4. 让Post携带表单参数
httpPost.setEntity(new UrlEncodedFormEntity(listValues, Consts.UTF_8));
​
// 5. 获取HttpResponse响应
CloseableHttpResponse response = httpClient.execute(httpPost);
​
// 6. 读response
System.out.println(EntityUtils.toString(response.getEntity()));
​
// 7. 释放资源
response.close();
httpClient.close();

封装好的HttpClient工具类：

package com.sky.utils;import com.alibaba.fastjson.JSONObject;
import org.apache.http.NameValuePair;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;/*** Http工具类*/
public class HttpClientUtil {static final  int TIMEOUT_MSEC = 5 * 1000;/*** 发送GET方式请求* @param url* @param paramMap* @return*/public static String doGet(String url,Map<String,String> paramMap){// 创建Httpclient对象CloseableHttpClient httpClient = HttpClients.createDefault();String result = "";CloseableHttpResponse response = null;try{URIBuilder builder = new URIBuilder(url);if(paramMap != null){for (String key : paramMap.keySet()) {builder.addParameter(key,paramMap.get(key));}}URI uri = builder.build();//创建GET请求HttpGet httpGet = new HttpGet(uri);//发送请求response = httpClient.execute(httpGet);//判断响应状态if(response.getStatusLine().getStatusCode() == 200){result = EntityUtils.toString(response.getEntity(),"UTF-8");}}catch (Exception e){e.printStackTrace();}finally {try {response.close();httpClient.close();} catch (IOException e) {e.printStackTrace();}}return result;}/*** 发送POST方式请求* @param url* @param paramMap* @return* @throws IOException*/public static String doPost(String url, Map<String, String> paramMap) throws IOException {// 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 (paramMap != null) {List<NameValuePair> paramList = new ArrayList();for (Map.Entry<String, String> param : paramMap.entrySet()) {paramList.add(new BasicNameValuePair(param.getKey(), param.getValue()));}// 模拟表单UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);httpPost.setEntity(entity);}httpPost.setConfig(builderRequestConfig());// 执行http请求response = httpClient.execute(httpPost);resultString = EntityUtils.toString(response.getEntity(), "UTF-8");} catch (Exception e) {throw e;} finally {try {response.close();} catch (IOException e) {e.printStackTrace();}}return resultString;}/*** 发送POST方式请求* @param url* @param paramMap* @return* @throws IOException*/public static String doPost4Json(String url, Map<String, String> paramMap) throws IOException {// 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);if (paramMap != null) {//构造json格式数据JSONObject jsonObject = new JSONObject();for (Map.Entry<String, String> param : paramMap.entrySet()) {jsonObject.put(param.getKey(),param.getValue());}StringEntity entity = new StringEntity(jsonObject.toString(),"utf-8");//设置请求编码entity.setContentEncoding("utf-8");//设置数据类型entity.setContentType("application/json");httpPost.setEntity(entity);}httpPost.setConfig(builderRequestConfig());// 执行http请求response = httpClient.execute(httpPost);resultString = EntityUtils.toString(response.getEntity(), "UTF-8");} catch (Exception e) {throw e;} finally {try {response.close();} catch (IOException e) {e.printStackTrace();}}return resultString;}private static RequestConfig builderRequestConfig() {return RequestConfig.custom().setConnectTimeout(TIMEOUT_MSEC).setConnectionRequestTimeout(TIMEOUT_MSEC).setSocketTimeout(TIMEOUT_MSEC).build();}}