HttpClient作用：

• 发送HTTP请求

• 接收响应数据

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HttpClient应用场景：

使用扫描支付、查看地图、获取验证码、查看天气等功能,需要发起请求的时候

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实现HttpClient

• HttpClient的maven坐标：

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

HttpClient的核心API：

• HttpClient：Http客户端对象类型，使用该类型对象可发起Http请求。

• HttpClients：可认为是构建器，可创建HttpClient对象。

• CloseableHttpClient：实现类，实现了HttpClient接口。

• HttpGet：Get方式请求类型。

• HttpPost：Post方式请求类型。

请求样例Get

package com.sky.test;import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;@SpringBootTest
public class HttpClientTest {/*** 测试通过httpclient发送GET方式的请求*/@Testpublic void testGET() throws Exception{//创建httpclient对象CloseableHttpClient httpClient = HttpClients.createDefault();//创建请求对象HttpGet httpGet = new HttpGet("http://localhost:8080/user/shop/status");//发送请求，接受响应结果CloseableHttpResponse response = httpClient.execute(httpGet);//获取服务端返回的状态码int statusCode = response.getStatusLine().getStatusCode();System.out.println("服务端返回的状态码为：" + statusCode);HttpEntity entity = response.getEntity();String body = EntityUtils.toString(entity);System.out.println("服务端返回的数据为：" + body);//关闭资源response.close();httpClient.close();}
}

POST

	/*** 测试通过httpclient发送POST方式的请求*/@Testpublic void testPOST() throws Exception{// 创建httpclient对象CloseableHttpClient httpClient = HttpClients.createDefault();//创建请求对象HttpPost httpPost = new HttpPost("http://localhost:8080/admin/employee/login");JSONObject jsonObject = new JSONObject();jsonObject.put("username","admin");jsonObject.put("password","123456");StringEntity entity = new StringEntity(jsonObject.toString());//指定请求编码方式entity.setContentEncoding("utf-8");//数据格式entity.setContentType("application/json");httpPost.setEntity(entity);//发送请求CloseableHttpResponse response = httpClient.execute(httpPost);//解析返回结果int statusCode = response.getStatusLine().getStatusCode();System.out.println("响应码为：" + statusCode);HttpEntity entity1 = response.getEntity();//使用EntityUtils对请求结果进行解析String body = EntityUtils.toString(entity1);System.out.println("响应数据为：" + body);//关闭资源response.close();httpClient.close();}

封装的实体类 

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();}}