目前JAVA实现HTTP请求的方法用的最多的有两种：
第一种是java原生HttpURLConnection
import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;public class HttpClient { 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：get connection.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; } 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true connection.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 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; }}第二种是apache httpClient4.5
import java.io.IOException;import java.io.UnsupportedEncodingException;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.Map.Entry;import java.util.Set;import org.apache.http.HttpEntity;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.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.message.BasicNameValuePair;import org.apache.http.util.EntityUtils;public class HttpClient4 { public static String doGet(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 doPost(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entity Set<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; }}有时候我们在使用post请求时，可能传入的参数是json或者其他格式，此时我们则需要更改请求头及参数的设置信息，以httpClient4.5为例，更改下面两列配置：httpPost.setEntity(new StringEntity("你的json串")); httpPost.addHeader("Content-Type", "application/json")。
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