使用HttpClient模拟HTTP发送POST或GET请求

在Java开发中，服务与服务之间进行调用，需要使用HttpClient发送HTTP请求，以下是使用Java实现模拟HTTP发送POST或GET请求的代码

1、pom.xml中导入HTTP依赖

    <!-- HTTP请求依赖 --><dependency><groupId>org.apache.httpcomponents</groupId><artifactId>httpclient</artifactId><version>4.5.2</version></dependency><!-- json依赖 --><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.47</version></dependency>

2、发送Post或get请求
需要传参数时注意：文本参数用StringEntity,参数放入json对象里面，文件参数用MultipartEntityBuilder

package com.dascom.smallroutine.utils;
import java.io.IOException;
import com.alibaba.fastjson.JSONObject;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.ResponseHandler;
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.entity.StringEntity;
import org.apache.http.impl.client.BasicResponseHandler;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;public class HttpClientUtil {//日志输出private static Logger logger = LogManager.getLogger(HttpClientUtil.class);/*** 发送get请求 调用这个方法* @param url* @return str //返回请求的内容* @throws Exception*/public static String doGet(String url){// 创建Httpclient对象CloseableHttpClient httpClient = HttpClients.createDefault();;String returnValue = null;// 创建http GET请求HttpGet httpGet = new HttpGet(url);CloseableHttpResponse response = null;try {//执行请求response = httpClient.execute(httpGet);//判断返回状态是否为200if(response.getStatusLine().getStatusCode() == 200) {//请求体内容returnValue = EntityUtils.toString(response.getEntity(), "UTF-8");return returnValue;}} catch (ClientProtocolException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {if (response != null) {try {response.close();} catch (IOException e) {logger.error("response关闭失败！");e.printStackTrace();}}try {httpClient.close();} catch (IOException e) {logger.error("httpClient关闭失败！");e.printStackTrace();}}return returnValue;}/*** 发送Post请求 调用这个方法 带json参数* @param url   要请求的地址* @param json    要发送的json格式数据* @return 返回的数据*/public static String doPostWithJson(String url,JSONObject json){String returnValue = null;CloseableHttpClient httpclient = null;ResponseHandler<String> responseHandler = new BasicResponseHandler();try {//创建httpclient对象httpclient = HttpClients.createDefault();//创建http POST请求HttpPost httpPost = new HttpPost(url);//文本参数用StringEntity,文件参数用MultipartEntityBuilderStringEntity requestEntity = new StringEntity(json.toJSONString(),"utf-8");requestEntity.setContentEncoding("UTF-8");httpPost.setHeader("Content-type","application/json");//请求头httpPost.setEntity(requestEntity);//发送请求，获取返回值returnValue = httpclient.execute(httpPost,responseHandler);}catch (Exception e) {logger.error("发送post请求失败！"+e.getMessage());}finally {try {httpclient.close();} catch (IOException e) {logger.error("httpclient关闭失败！"+e.getMessage());}}return returnValue;}
}

3、测试类

public class Test {public static void main(String[] args) {//GET请求访问HttpClientUtil.doGet("http://baidu.com");//POST请求访问JSONObject json = new JSONObject();json.put("data", "成功");//参数HttpClientUtil.doPostWithJson("http://baidu.com", json);}
}

如果要请求有文件参数接口，例子如下

代码实现

package com.example.demo.controller;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import org.apache.http.HttpEntity;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.impl.client.BasicResponseHandler;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import com.alibaba.fastjson.JSONObject;
@RestController
@RequestMapping("/v1.0")
public class PrintController {//日志输出private static Logger logger = LogManager.getLogger(PrintController.class);@RequestMapping(value="/monitprint",method=RequestMethod.POST,produces ="application/json;charset=utf-8")public JSONObject monitoringPrint(@RequestParam(required=false) MultipartFile file) {       //POST请求访问JSONObject json = new JSONObject();      String s=PrintController.doPostWithJson("http://127.0.0.1:20173/v2.0/print/0015CA7350020300", file); if(s!=null&&!"".equals(s)) {json.put("data", "访问成功");}else{json.put("data", "访问失败");}    return json;}/*** 发送Post请求 调用这个方法 带json参数* @param url  要请求的地址* @param json    要发送的json格式数据* @return 返回的数据*/public static String doPostWithJson(String url,MultipartFile Mfile){String returnValue = null;CloseableHttpClient httpclient = null;ResponseHandler<String> responseHandler = new BasicResponseHandler();try {//创建httpclient对象httpclient = HttpClients.createDefault();//创建http POST请求HttpPost httpPost = new HttpPost(url);//文本参数用StringEntity,文件参数用MultipartEntityBuilderMultipartEntityBuilder builder = MultipartEntityBuilder.create();//MultipartFile转FileFile file=multipartFileToFile(Mfile);builder.addBinaryBody("file", file);httpPost.setHeader("File-Type","pdf");//请求头HttpEntity reqEntity = builder.build();httpPost.setEntity(reqEntity);//发送请求，获取返回值returnValue = httpclient.execute(httpPost,responseHandler);}catch (Exception e) {logger.error("发送post请求失败！"+e.getMessage());}finally {try {httpclient.close();} catch (IOException e) {logger.error("httpclient关闭失败！"+e.getMessage());}}return returnValue;}/*** MultipartFile 转 File* @param file* @throws Exception*/public static File multipartFileToFile(MultipartFile file) throws Exception {File toFile = null;if (file.equals("") || file.getSize() <= 0) {file = null;} else {InputStream ins = null;ins = file.getInputStream();toFile = new File(file.getOriginalFilename());inputStreamToFile(ins, toFile);ins.close();}return toFile;}/*** 获取流文件* @param ins* @param file*/private static void inputStreamToFile(InputStream ins, File file) {try {OutputStream os = new FileOutputStream(file);int bytesRead = 0;byte[] buffer = new byte[8192];while ((bytesRead = ins.read(buffer, 0, 8192)) != -1) {os.write(buffer, 0, bytesRead);}os.close();ins.close();} catch (Exception e) {e.printStackTrace();}}
}

4、x-www-form-urlencoded类型的参数

实现代码

public class Test {public static void main(String[] args) {List<NameValuePair> params = new ArrayList<NameValuePair>();NameValuePair pair = new BasicNameValuePair("grant_type", "client_credentials");NameValuePair pair2 = new BasicNameValuePair("app_key", "YLbbATeusEJbPCZiZ1n6paICffMu");NameValuePair pair3 = new BasicNameValuePair("app_secret", "oR93ABEWRDAIldXpZ6W4EbOvmV8NfKiMPl3OcO8U41yjeXNGaNNgr1xC4DGe5");params.add(pair);params.add(pair2);params.add(pair3);String postForString = postWithParamsForString("https://openapi.italent.cn/token", params);System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>post:"+postForString);}
}
//POST请求
public static String postWithParamsForString(String url, List<NameValuePair> params){HttpClient client = HttpClients.createDefault();HttpPost httpPost =   new HttpPost(url);String s = "";try {httpPost.setEntity(new UrlEncodedFormEntity(params,"UTF-8"));httpPost.setHeader("Content-type", "application/x-www-form-urlencoded");HttpResponse response = client.execute(httpPost);int statusCode = response.getStatusLine().getStatusCode();if(statusCode==200){HttpEntity entity = response.getEntity();s = EntityUtils.toString(entity);}} catch (IOException e) {e.printStackTrace();}return s;}

欢迎大家阅读，本人见识有限，写的博客难免有错误或者疏忽的地方，还望各位大佬指点，在此表示感谢。

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