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目前JAVA实现HTTP请求的方法用的最多的有两种：一种是通过HTTPClient这种第三方的开源框架去实现。HTTPClient对HTTP的封装性比较不错，通过它基本上能够满足我们大部分的需求，HttpClient3.1 是 org.apache.commons.httpclient下操作远程 url的工具包，虽然已不再更新，但实现工作中使用httpClient3.1的代码还是很多，HttpClient4.5是org.apache.http.client下操作远程 url的工具包，最新的；另一种则是通过HttpURLConnection去实现，HttpURLConnection是JAVA的标准类，是JAVA比较原生的一种实现方式。

 

第一种方式：java原生HttpURLConnection

package com.mobile.utils;import com.alibaba.fastjson.JSONObject;
import org.apache.log4j.Logger;import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.*;public class HttpUtil {static Logger log = Logger.getLogger(HttpUtil.class);/*** 向指定URL发送GET方法的请求** @param httpurl*            请求参数用?拼接在url后边，请求参数应该是 name1=value1&name2=value2 的形式。* @return result 所代表远程资源的响应结果*/public static String doGet(String httpurl) {HttpURLConnection connection = null;InputStream is = null;BufferedReader br = null;String result = null;// 返回结果字符串try {// 创建远程url连接对象URL url = new URL(httpurl);// 通过远程url连接对象打开一个连接，强转成httpURLConnection类connection = (HttpURLConnection) url.openConnection();// 设置连接方式：getconnection.setRequestMethod("GET");// 设置连接主机服务器的超时时间：15000毫秒connection.setConnectTimeout(15000);// 设置读取远程返回的数据时间：60000毫秒connection.setReadTimeout(60000);// 发送请求
            connection.connect();// 通过connection连接，获取输入流if (connection.getResponseCode() == 200) {is = connection.getInputStream();// 封装输入流is，并指定字符集br = new BufferedReader(new InputStreamReader(is, "UTF-8"));// 存放数据StringBuffer sbf = new StringBuffer();String temp = null;while ((temp = br.readLine()) != null) {sbf.append(temp);sbf.append("\r\n");}result = sbf.toString();}} catch (MalformedURLException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 关闭资源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}connection.disconnect();// 关闭远程连接
        }return result;}/*** 向指定 URL 发送POST方法的请求** @param httpUrl*            发送请求的 URL* @param param*            请求参数应该是{"key":"==g43sEvsUcbcunFv3mHkIzlHO4iiUIT R7WwXuSVKTK0yugJnZSlr6qNbxsL8OqCUAFyCDCoRKQ882m6cTTi0q9uCJsq JJvxS+8mZVRP/7lWfEVt8/N9mKplUA68SWJEPSXyz4MDeFam766KEyvqZ99d"}的形式。* @return 所代表远程资源的响应结果*/public static String doPost(String httpUrl, String param) {HttpURLConnection connection = null;InputStream is = null;OutputStream os = null;BufferedReader br = null;String result = null;try {URL url = new URL(httpUrl);// 通过远程url连接对象打开连接connection = (HttpURLConnection) url.openConnection();// 设置连接请求方式connection.setRequestMethod("POST");// 设置连接主机服务器超时时间：15000毫秒connection.setConnectTimeout(15000);// 设置读取主机服务器返回数据超时时间：60000毫秒connection.setReadTimeout(60000);// 默认值为：false，当向远程服务器传送数据/写数据时，需要设置为trueconnection.setDoOutput(true);// 默认值为：true，当前向远程服务读取数据时，设置为true，该参数可有可无connection.setDoInput(true);// 设置传入参数的格式:请求参数应该是 name1=value1&name2=value2 的形式。connection.setRequestProperty("Content-Type", "application/json");// 设置鉴权信息：Authorization: Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0//connection.setRequestProperty("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");// 通过连接对象获取一个输出流os = connection.getOutputStream();// 通过输出流对象将参数写出去/传输出去,它是通过字节数组写出的
            os.write(param.getBytes());// 通过连接对象获取一个输入流，向远程读取if (connection.getResponseCode() == 200) {is = connection.getInputStream();// 对输入流对象进行包装:charset根据工作项目组的要求来设置br = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String temp = null;// 循环遍历一行一行读取数据while ((temp = br.readLine()) != null) {sbf.append(temp);sbf.append("\r\n");}result = sbf.toString();}} catch (MalformedURLException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 关闭资源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != os) {try {os.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}// 断开与远程地址url的连接
            connection.disconnect();}return result;}/**** @param httpUrl  请求的url* @param param  form表单的参数（key,value形式）* @return*/public static String doPostForm(String httpUrl, Map param) {HttpURLConnection connection = null;InputStream is = null;OutputStream os = null;BufferedReader br = null;String result = null;try {URL url = new URL(httpUrl);// 通过远程url连接对象打开连接connection = (HttpURLConnection) url.openConnection();// 设置连接请求方式connection.setRequestMethod("POST");// 设置连接主机服务器超时时间：15000毫秒connection.setConnectTimeout(15000);// 设置读取主机服务器返回数据超时时间：60000毫秒connection.setReadTimeout(60000);// 默认值为：false，当向远程服务器传送数据/写数据时，需要设置为trueconnection.setDoOutput(true);// 默认值为：true，当前向远程服务读取数据时，设置为true，该参数可有可无connection.setDoInput(true);// 设置传入参数的格式:请求参数应该是 name1=value1&name2=value2 的形式。connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");// 设置鉴权信息：Authorization: Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0//connection.setRequestProperty("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");// 通过连接对象获取一个输出流os = connection.getOutputStream();// 通过输出流对象将参数写出去/传输出去,它是通过字节数组写出的(form表单形式的参数实质也是key,value值的拼接，类似于get请求参数的拼接)
            os.write(createLinkString(param).getBytes());// 通过连接对象获取一个输入流，向远程读取if (connection.getResponseCode() == 200) {is = connection.getInputStream();// 对输入流对象进行包装:charset根据工作项目组的要求来设置br = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String temp = null;// 循环遍历一行一行读取数据while ((temp = br.readLine()) != null) {sbf.append(temp);sbf.append("\r\n");}result = sbf.toString();}} catch (MalformedURLException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 关闭资源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != os) {try {os.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}// 断开与远程地址url的连接
            connection.disconnect();}return result;}/*** 把数组所有元素排序，并按照“参数=参数值”的模式用“&”字符拼接成字符串* @param params 需要排序并参与字符拼接的参数组* @return 拼接后字符串*/public static String createLinkString(Map<String, String> params) {List<String> keys = new ArrayList<String>(params.keySet());Collections.sort(keys);StringBuilder prestr = new StringBuilder();for (int i = 0; i < keys.size(); i++) {String key = keys.get(i);String value = params.get(key);if (i == keys.size() - 1) {// 拼接时，不包括最后一个&字符prestr.append(key).append("=").append(value);} else {prestr.append(key).append("=").append(value).append("&");}}return prestr.toString();}public static void main(String[] args) {String url = "http://localhost:8082/api/conf/findConfList?type=1";String getResult = HttpUtil.doGet(url);System.out.println(getResult);url = "http://localhost:8082/api/core/login";JSONObject json = new JSONObject();json.put("key", "==g43sEvsUcbcunFv3mHkIzlHO4iiUIT R7WwXuSVKTK0yugJnZSlr6qNbxsL8OqCUAFyCDCoRKQ882m6cTTi0q9uCJsq JJvxS+8mZVRP/7lWfEVt8/N9mKplUA68SWJEPSXyz4MDeFam766KEyvqZ99d");String postResult = HttpUtil.doPost(url, json.toJSONString());System.out.println(postResult);url = "http://localhost:8082/api/test/testSendForm";Map<String,String> map = new HashMap<>();map.put("name", "测试表单请求");String formResult = HttpUtil.doPostForm(url, map);System.out.println(formResult);}}

以上包括了get请求和post请求以及form表单请求 

 

第二种方式：apache HttpClient 3.1

package com.demo.httpClient;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;import org.apache.commons.httpclient.DefaultHttpMethodRetryHandler;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;public class HttpClient3 {public static String doGet(String url) {// 输入流InputStream is = null;BufferedReader br = null;String result = null;// 创建httpClient实例HttpClient httpClient = new HttpClient();// 设置http连接主机服务超时时间：15000毫秒// 先获取连接管理器对象，再获取参数对象,再进行参数的赋值httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);// 创建一个Get方法实例对象GetMethod getMethod = new GetMethod(url);// 设置get请求超时为60000毫秒getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);// 设置请求重试机制，默认重试次数：3次，参数设置为true，重试机制可用，false相反getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(3, true));try {// 执行Get方法int statusCode = httpClient.executeMethod(getMethod);// 判断返回码if (statusCode != HttpStatus.SC_OK) {// 如果状态码返回的不是ok,说明失败了,打印错误信息System.err.println("Method faild: " + getMethod.getStatusLine());} else {// 通过getMethod实例，获取远程的一个输入流is = getMethod.getResponseBodyAsStream();// 包装输入流br = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();// 读取封装的输入流String temp = null;while ((temp = br.readLine()) != null) {sbf.append(temp).append("\r\n");}result = sbf.toString();}} catch (IOException e) {e.printStackTrace();} finally {// 关闭资源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}// 释放连接
            getMethod.releaseConnection();}return result;}public static String doPost(String url, Map<String, Object> paramMap) {// 获取输入流InputStream is = null;BufferedReader br = null;String result = null;// 创建httpClient实例对象HttpClient httpClient = new HttpClient();// 设置httpClient连接主机服务器超时时间：15000毫秒httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);// 创建post请求方法实例对象PostMethod postMethod = new PostMethod(url);// 设置post请求超时时间postMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);NameValuePair[] nvp = null;// 判断参数map集合paramMap是否为空if (null != paramMap && paramMap.size() > 0) {// 不为空// 创建键值参数对象数组，大小为参数的个数nvp = new NameValuePair[paramMap.size()];// 循环遍历参数集合mapSet<Entry<String, Object>> entrySet = paramMap.entrySet();// 获取迭代器Iterator<Entry<String, Object>> iterator = entrySet.iterator();int index = 0;while (iterator.hasNext()) {Entry<String, Object> mapEntry = iterator.next();// 从mapEntry中获取key和value创建键值对象存放到数组中try {nvp[index] = new NameValuePair(mapEntry.getKey(),new String(mapEntry.getValue().toString().getBytes("UTF-8"), "UTF-8"));} catch (UnsupportedEncodingException e) {e.printStackTrace();}index++;}}// 判断nvp数组是否为空if (null != nvp && nvp.length > 0) {// 将参数存放到requestBody对象中
            postMethod.setRequestBody(nvp);}// 执行POST方法try {int statusCode = httpClient.executeMethod(postMethod);// 判断是否成功if (statusCode != HttpStatus.SC_OK) {System.err.println("Method faild: " + postMethod.getStatusLine());}// 获取远程返回的数据is = postMethod.getResponseBodyAsStream();// 封装输入流br = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String temp = null;while ((temp = br.readLine()) != null) {sbf.append(temp).append("\r\n");}result = sbf.toString();} catch (IOException e) {e.printStackTrace();} finally {// 关闭资源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}// 释放连接
            postMethod.releaseConnection();}return result;}
}

 

第三种方式：apache  httpClient4.5

package com.mobile.utils;import com.alibaba.fastjson.JSONObject;
import org.apache.commons.io.IOUtils;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
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.entity.StringEntity;
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.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import org.apache.log4j.Logger;import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.*;
import java.util.Map.Entry;public class HttpUtil {static Logger log = Logger.getLogger(HttpUtil.class);public static void main(String[] args) {String url = "http://localhost:8082/api/conf/findConfList?type=1";String getResult = HttpUtil.getData(url);System.out.println(getResult);url = "http://localhost:8082/api/core/login";JSONObject json = new JSONObject();json.put("key", "==g43sEvsUcbcunFv3mHkIzlHO4iiUIT R7WwXuSVKTK0yugJnZSlr6qNbxsL8OqCUAFyCDCoRKQ882m6cTTi0q9uCJsq JJvxS+8mZVRP/7lWfEVt8/N9mKplUA68SWJEPSXyz4MDeFam766KEyvqZ99d");String postResult = HttpUtil.postData(url, json);System.out.println(postResult);url = "http://localhost:8082/api/test/testSendForm?format=json";Map<String, Object> map = new HashMap<>();map.put("name", "测试表单请求");String formResult = HttpUtil.sendxwwwForm(url, map);System.out.println(formResult);}public static String getData(String url) {CloseableHttpClient httpClient = null;CloseableHttpResponse response = null;String result = "";try {// 通过址默认配置创建一个httpClient实例httpClient = HttpClients.createDefault();// 创建httpGet远程连接实例HttpGet httpGet = new HttpGet(url);// 设置请求头信息，鉴权httpGet.setHeader("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");// 设置配置请求参数RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(35000)// 连接主机服务超时时间.setConnectionRequestTimeout(35000)// 请求超时时间.setSocketTimeout(60000)// 数据读取超时时间
                    .build();// 为httpGet实例设置配置
            httpGet.setConfig(requestConfig);// 执行get请求得到返回对象response = httpClient.execute(httpGet);// 通过返回对象获取返回数据HttpEntity entity = response.getEntity();// 通过EntityUtils中的toString方法将结果转换为字符串result = EntityUtils.toString(entity);} catch (ClientProtocolException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 关闭资源if (null != response) {try {response.close();} catch (IOException e) {e.printStackTrace();}}if (null != httpClient) {try {httpClient.close();} catch (IOException e) {e.printStackTrace();}}}return result;}public static String postData(String url, Map<String, Object> paramMap) {HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();HttpPost post = new HttpPost(url);String result = "";try (CloseableHttpClient closeableHttpClient = httpClientBuilder.build()) {// HttpEntity entity = new StringEntity(jsonStrData);// 修复 POST json 导致中文乱码HttpEntity entity = new StringEntity(paramMap.toString(), "UTF-8");post.setEntity(entity);post.setHeader("Content-type", "application/json");HttpResponse resp = closeableHttpClient.execute(post);try {InputStream respIs = resp.getEntity().getContent();byte[] respBytes = IOUtils.toByteArray(respIs);result = new String(respBytes, Charset.forName("UTF-8"));} catch (Exception e) {e.printStackTrace();}return result;} catch (IOException e) {e.printStackTrace();}return result;}/*** form表单提交* @param url* @param paramMap* @return*/public static String sendxwwwform(String url, Map<String, Object> paramMap) {CloseableHttpClient httpClient = null;CloseableHttpResponse httpResponse = null;String result = "";// 创建httpClient实例httpClient = HttpClients.createDefault();// 创建httpPost远程连接实例HttpPost httpPost = new HttpPost(url);// 配置请求参数实例RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(35000)// 设置连接主机服务超时时间.setConnectionRequestTimeout(35000)// 设置连接请求超时时间.setSocketTimeout(60000)// 设置读取数据连接超时时间
                .build();// 为httpPost实例设置配置
        httpPost.setConfig(requestConfig);// 设置请求头httpPost.addHeader("Content-Type", "application/x-www-form-urlencoded");// 封装post请求参数if (null != paramMap && paramMap.size() > 0) {List<NameValuePair> nvps = new ArrayList<NameValuePair>();// 通过map集成entrySet方法获取entitySet<Entry<String, Object>> entrySet = paramMap.entrySet();// 循环遍历，获取迭代器Iterator<Entry<String, Object>> iterator = entrySet.iterator();while (iterator.hasNext()) {Entry<String, Object> mapEntry = iterator.next();nvps.add(new BasicNameValuePair(mapEntry.getKey(), mapEntry.getValue().toString()));}// 为httpPost设置封装好的请求参数try {httpPost.setEntity(new UrlEncodedFormEntity(nvps, "UTF-8"));} catch (UnsupportedEncodingException e) {e.printStackTrace();}}try {// httpClient对象执行post请求,并返回响应参数对象httpResponse = httpClient.execute(httpPost);// 从响应对象中获取响应内容HttpEntity entity = httpResponse.getEntity();result = EntityUtils.toString(entity);} catch (ClientProtocolException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 关闭资源if (null != httpResponse) {try {httpResponse.close();} catch (IOException e) {e.printStackTrace();}}if (null != httpClient) {try {httpClient.close();} catch (IOException e) {e.printStackTrace();}}}return result;}}

以上包括了get请求和post请求以及form表单请求 

 

此外还可以设置添加自定义请求头（有的接口需要登录验证）：

　　方式一：

 //设置自定义请求头if (headerMap != null) {for (Map.Entry<String, String> entry : headerMap.entrySet()) {connection.setRequestProperty(entry.getKey(),entry.getValue());}}

　　方式三：

if (headers != null) {for (Map.Entry<String, String> entry : headers.entrySet()) {httpPost.addHeader(entry.getKey(),entry.getValue());}}

　　

转载自https://www.cnblogs.com/hhhshct/p/8523697.html

测试后，稍作改动及添加

httpurlconnection和httpclient区别：https://www.cnblogs.com/liushuibufu/p/4140913.html