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Java工具类--通过HttpClient发送http请求

article 2025/6/28 11:03:06

在写网络程序的时候，经常会有从网址获取数据的需求，上一篇解析JSON就需要从百度获取天气数据，本文介绍一种Java发送http请求的工具–HttpClient。

HttpClient的介绍

The most essential function of HttpClient is to execute HTTP methods. Execution of an HTTP method involves one or several HTTP request / HTTP response exchanges, usually handled internally by HttpClient. The user is expected to provide a request object to execute and HttpClient is expected to transmit the request to the target server return a corresponding response object, or throw an exception if execution was unsuccessful.

HttpClient最基本的功能就是执行http方法，执行http方法包括了一次或者几次HTTP请求和相应的变化，通常也是通过HttpClient来处理的。只要用户提供一个request的对象，HttpClient就会将用户的请求发送到目标服务器上，并且返回一个respone对象，如果没有执行成功将抛出一个异常。

通过文档的介绍我们可以知道，发送HTTP请求一般可以分为以下步骤

  1. 取得HttpClient对象
  2. 封装http请求
  3. 执行http请求
  4. 处理结果

其中可以发送的请求类型有GET, HEAD, POST, PUT, DELETE, TRACE 和 OPTIONS

HttpClient supports out of the box all HTTP methods defined in the HTTP/1.1 specification: GET, HEAD, POST, PUT, DELETE, TRACE and OPTIONS.

官方文档中的示例

//1.获得一个httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
//2.生成一个get请求
HttpGet httpget = new HttpGet("http://localhost/");
//3.执行get请求并返回结果
CloseableHttpResponse response = httpclient.execute(httpget);
try {//4.处理结果
} finally {response.close();
}

介绍一下最常用的HttpGet和HttpPost。
RESTful提倡，通过HTTP请求对应的POST、GET、PUT、DELETE来完成对应的CRUD操作。
所以本文介绍一下通过GET获取数据和POST提交数据的实现方法。

##发送HttpGet
先介绍发送HttpGet请求

	/*** 发送HttpGet请求* @param url* @return*/public static String sendGet(String url) {//1.获得一个httpclient对象CloseableHttpClient httpclient = HttpClients.createDefault();//2.生成一个get请求HttpGet httpget = new HttpGet(url);CloseableHttpResponse response = null;try {//3.执行get请求并返回结果response = httpclient.execute(httpget);} catch (IOException e1) {e1.printStackTrace();}String result = null;try {//4.处理结果，这里将结果返回为字符串HttpEntity entity = response.getEntity();if (entity != null) {result = EntityUtils.toString(entity);}} catch (ParseException | IOException e) {e.printStackTrace();} finally {try {response.close();} catch (IOException e) {e.printStackTrace();}}return result;}

##发送HttpPost
发送HttpPost的方法和发送HttpGet很类似，只是将请求类型给位HttpPost即可。
代码如下

	/*** 发送不带参数的HttpPost请求* @param url* @return*/public static String sendPost(String url) {//1.获得一个httpclient对象CloseableHttpClient httpclient = HttpClients.createDefault();//2.生成一个post请求HttpPost httppost = new HttpPost(url);CloseableHttpResponse response = null;try {//3.执行get请求并返回结果response = httpclient.execute(httppost);} catch (IOException e) {e.printStackTrace();}//4.处理结果，这里将结果返回为字符串HttpEntity entity = response.getEntity();String result = null;try {result = EntityUtils.toString(entity);} catch (ParseException | IOException e) {e.printStackTrace();}return result;}

带参数的HttpPost

发送带参数的HttpPost

Many applications need to simulate the process of submitting an HTML form, for instance, in order to log in to a web application or submit input data. HttpClient provides the entity class UrlEncodedFormEntity to facilitate the process.

HttpClient通过UrlEncodedFormEntity，来提交带参数的请求

将需要提交的参数放在map里
代码如下

	/*** 发送HttpPost请求，参数为map* @param url* @param map* @return*/public static String sendPost(String url, Map<String, String> map) {CloseableHttpClient httpclient = HttpClients.createDefault();List<NameValuePair> formparams = new ArrayList<NameValuePair>();for (Map.Entry<String, String> entry : map.entrySet()) {//给参数赋值formparams.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));}UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, Consts.UTF_8);HttpPost httppost = new HttpPost(url);httppost.setEntity(entity);CloseableHttpResponse response = null;try {response = httpclient.execute(httppost);} catch (IOException e) {e.printStackTrace();}HttpEntity entity1 = response.getEntity();String result = null;try {result = EntityUtils.toString(entity1);} catch (ParseException | IOException e) {e.printStackTrace();}return result;}

完整代码

完成代码如下，用到的jar包有httpclient-4.5.1.jar，httpcore-4.4.3.jar，依赖的jar有commons-logging-1.2.jar
注意是Apache HttpClient，不是commons-httpclient

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
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.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
/*** @author GWCheng**/
public class HttpUtil {private static final CloseableHttpClient httpclient = HttpClients.createDefault();/*** 发送HttpGet请求* @param url* @return*/public static String sendGet(String url) {HttpGet httpget = new HttpGet(url);CloseableHttpResponse response = null;try {response = httpclient.execute(httpget);} catch (IOException e1) {e1.printStackTrace();}String result = null;try {HttpEntity entity = response.getEntity();if (entity != null) {result = EntityUtils.toString(entity);}} catch (ParseException | IOException e) {e.printStackTrace();} finally {try {response.close();} catch (IOException e) {e.printStackTrace();}}return result;}/*** 发送HttpPost请求，参数为map* @param url* @param map* @return*/public static String sendPost(String url, Map<String, String> map) {List<NameValuePair> formparams = new ArrayList<NameValuePair>();for (Map.Entry<String, String> entry : map.entrySet()) {formparams.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));}UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, Consts.UTF_8);HttpPost httppost = new HttpPost(url);httppost.setEntity(entity);CloseableHttpResponse response = null;try {response = httpclient.execute(httppost);} catch (IOException e) {e.printStackTrace();}HttpEntity entity1 = response.getEntity();String result = null;try {result = EntityUtils.toString(entity1);} catch (ParseException | IOException e) {e.printStackTrace();}return result;}/*** 发送不带参数的HttpPost请求* @param url* @return*/public static String sendPost(String url) {HttpPost httppost = new HttpPost(url);CloseableHttpResponse response = null;try {response = httpclient.execute(httppost);} catch (IOException e) {e.printStackTrace();}HttpEntity entity = response.getEntity();String result = null;try {result = EntityUtils.toString(entity);} catch (ParseException | IOException e) {e.printStackTrace();}return result;}}

测试用例

服务器端代码

@Controller
@RequestMapping("/test")
// /test/**
public class TestController {// /test/view post 提交数据，模拟表单@RequestMapping(value = "/view", method = RequestMethod.POST)public void viewTest(PrintWriter out, HttpServletResponse response, @RequestParam("param1") String param1,@RequestParam("param2") String param2) {response.setContentType("application/json;charset=UTF-8");Gson gson = new GsonBuilder().create();Map<String, Object> map = new HashMap<String, Object>();map.put("param1", param1);map.put("param2", param2);System.out.println(gson.toJson(map));out.print(gson.toJson(map));}// /test/view?param1=aaa&param2=bbb get @RequestMapping(value = "/view", method = RequestMethod.GET)public void viewTest3(PrintWriter out, HttpServletResponse response, @RequestParam("param1") String param1,@RequestParam("param2") String param2) {response.setContentType("application/json;charset=UTF-8");Gson gson = new GsonBuilder().create();Map<String, Object> map = new HashMap<String, Object>();map.put("param1", param1);map.put("param2", param2);System.out.println(gson.toJson(map));out.print(gson.toJson(map));}// /test/view2/{courseId}@RequestMapping(value = "/view2/{param}", method = RequestMethod.GET)public void viewTest1(PrintWriter out, HttpServletResponse response, @PathVariable("param") String param) {response.setContentType("application/json;charset=UTF-8");Gson gson = new GsonBuilder().create();Map<String, Object> map = new HashMap<String, Object>();map.put("param", param);out.print(gson.toJson(map));}// /test/view3@RequestMapping(value = "/view3", method = RequestMethod.POST)public void viewTest2(PrintWriter out, HttpServletResponse response) {response.setContentType("application/json;charset=UTF-8");Gson gson = new GsonBuilder().create();Map<String, Object> map = new HashMap<String, Object>();map.put("status", "success");out.print(gson.toJson(map));}}

测试代码

public class HttpClientTest {@Testpublic void testGet() {//百度天气的api//String url1 = "http://api.map.baidu.com/telematics/v3/weather?location=%E5%8C%97%E4%BA%AC&output=json&ak=W69oaDTCfuGwzNwmtVvgWfGH";String url1 = "http://localhost:8080/wechat/test/view2/你好世界";String result1 = HttpUtil.sendGet(url1);System.out.println(result1);//输出{"param":"你好世界"}}@Testpublic void testPost() throws UnsupportedEncodingException{String url = "http://localhost:8080/wechat/test/view";Map<String,String> map = new HashMap<String,String>();map.put("param1", "你好世界");map.put("param2", "哈哈");String result = HttpUtil.sendPost(url, map);System.out.println(result);//输出结果{"param1":"你好世界","param2":"哈哈"}}@Testpublic void testPost1() throws UnsupportedEncodingException{String url = "http://localhost:8080/wechat/test/view3";String result = HttpUtil.sendPost(url);System.out.println(result);//输出结果{"status":"success"}}}

建议通过HttpGet获取信息，HttpPost提交信息，而HttpGet获取信息时需要提交的参数一般会在url中体现，或者以？传参，或者在url中传参，所以就没写HttpGet带参数的。也希望大家能遵循Http的设计原则，通过HttpGet, HttpPost, HttpPut, HttpDelete,来实现获取数据，提交数据，修改数据，和删除数据的方法。

2018年10月25修改

依赖

        <!--apache工具类--><dependency><groupId>org.apache.commons</groupId><artifactId>commons-lang3</artifactId><version>3.1</version></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-collections4</artifactId><version>4.1</version></dependency><!--lombok--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.2</version><scope>provided</scope></dependency><!--httpclient--><dependency><groupId>org.apache.httpcomponents</groupId><artifactId>httpclient</artifactId><version>4.5.6</version></dependency><dependency><groupId>org.apache.httpcomponents</groupId><artifactId>httpmime</artifactId><version>4.5.6</version></dependency><!--log--><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-api</artifactId><version>1.7.10</version></dependency><dependency><groupId>ch.qos.logback</groupId><artifactId>logback-classic</artifactId><version>1.1.2</version></dependency><dependency><groupId>ch.qos.logback</groupId><artifactId>logback-core</artifactId><version>1.1.2</version></dependency><!--MultipartFile--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId><version>2.0.6.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-test</artifactId><version>5.0.6.RELEASE</version></dependency>

最近优化了一下这个方法，具体程序如下

package com.cgw.util;import com.alibaba.fastjson.JSONObject;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.MapUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.http.Consts;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.client.config.RequestConfig;
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.config.ConnectionConfig;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.entity.mime.HttpMultipartMode;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.StringBody;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicHeader;
import org.apache.http.util.EntityUtils;
import org.springframework.mock.web.MockMultipartFile;
import org.springframework.web.multipart.MultipartFile;import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.charset.CodingErrorAction;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;/*** Http工具类** @author 程高伟*/
@Slf4j
public class HttpUtil {private static final String USER_AGENT = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36";// 超时设置private static final RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(5000).setConnectionRequestTimeout(5000).setSocketTimeout(10000).build();// 编码设置private static final ConnectionConfig connectionConfig = ConnectionConfig.custom().setMalformedInputAction(CodingErrorAction.IGNORE).setUnmappableInputAction(CodingErrorAction.IGNORE).setCharset(Consts.UTF_8).build();private static HttpClientBuilder getBuilder() {List<Header> headers = new ArrayList<>();Header header = new BasicHeader("User-Agent", USER_AGENT);headers.add(header);return HttpClients.custom().setDefaultConnectionConfig(connectionConfig).setDefaultHeaders(headers).setDefaultRequestConfig(requestConfig);}/*** 发送HttpGet请求** @param url 请求地址* @return*/public static String sendGet(String url) throws IOException {String result;HttpGet httpGet = new HttpGet(url);try (CloseableHttpClient httpclient = getBuilder().build();CloseableHttpResponse response = httpclient.execute(httpGet)) {HttpEntity httpEntity = response.getEntity();result = EntityUtils.toString(httpEntity);}return result;}/*** 发送HttpPost请求，参数为json字符串** @param url     请求地址* @param jsonStr json字符串* @return*/public static String sendPost(String url, String jsonStr) throws IOException {String result;// 设置entityStringEntity stringEntity = new StringEntity(jsonStr, Consts.UTF_8);stringEntity.setContentType("application/json");HttpPost httpPost = new HttpPost(url);httpPost.setEntity(stringEntity);try (CloseableHttpClient httpclient = getBuilder().build(); CloseableHttpResponse httpResponse = httpclient.execute(httpPost);) {HttpEntity httpEntity = httpResponse.getEntity();result = EntityUtils.toString(httpEntity);}return result;}/*** 发送HttpPost请求，提交表单，支持文件上传** @param url    请求地址* @param params 表单参数* @param files  上传文件* @return*/public static String sendPost(String url, Map<String, Object> params, List<MultipartFile> files) throws IOException {String result;// 设置entityMultipartEntityBuilder builder = MultipartEntityBuilder.create();builder.setCharset(Charset.forName("UTF-8"));builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);if (CollectionUtils.isNotEmpty(files)) { // 文件表单参数for (MultipartFile file : files) {Path path = Paths.get(file.getOriginalFilename());String contentType = Files.probeContentType(path);if (StringUtils.isEmpty(contentType)) {contentType = "application/octet-stream";}builder.addBinaryBody(file.getName(), file.getInputStream(), ContentType.create(contentType), file.getOriginalFilename());}}if (MapUtils.isNotEmpty(params)) { // 普通表单参数params.forEach((k, v) -> {StringBody stringBody = new StringBody(v.toString(), ContentType.create("text/plain", "UTF-8"));builder.addPart(k, stringBody);});}HttpPost httpPost = new HttpPost(url);httpPost.setEntity(builder.build());try (CloseableHttpClient httpclient = getBuilder().build();CloseableHttpResponse httpResponse = httpclient.execute(httpPost)) {HttpEntity httpEntity = httpResponse.getEntity();result = EntityUtils.toString(httpEntity);}return result;}// MultipartFile里面的name就是表单的name，文件名是originalFilenameprivate static MultipartFile fileToMultipartFile(File file, String name) throws IOException {log.info("File转MultipartFile：文件路径：{}", file.getAbsolutePath());FileInputStream inputStream = new FileInputStream(file);Path path = Paths.get(file.getAbsolutePath());String contentType = Files.probeContentType(path);if (StringUtils.isEmpty(contentType)) {contentType = "application/octet-stream";}MultipartFile multipartFile = new MockMultipartFile(name,file.getName(),contentType,inputStream);log.info("File转MultipartFile：转换后的文件信息：[name:{}, originalFilename:{} ,contentType:{}]",multipartFile.getName(),multipartFile.getOriginalFilename(),multipartFile.getContentType());return multipartFile;}public static void main(String[] args) throws IOException {String url = "http://127.0.0.1:8080/file/uploadSingle";Map<String, Object> params = new HashMap<>();params.put("userId", 123);params.put("username", "张三");List<MultipartFile> files = new ArrayList<>();MultipartFile file = fileToMultipartFile(new File("d:\\file\\中文.jpg"), "file");files.add(file);System.out.println(sendPost(url, params, files));}}

参考文献

HttpClient Tutorial

http://www.lryc.cn/news/2420778.html

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