• 第一种方式：java原生HttpURLConnection
• 第二种方式：apache HttpClient3.1
• 第三种方式：apache httpClient4.5

除了本文推荐的几种方式，强烈推荐 OkHttp

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。

自己在工作中三种方式都用到过，总结一下分享给大家，也方便自己以后使用，话不多说上代码。

第一种方式：java原生HttpURLConnection

package com.powerX.httpClient;
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;
 }
} 

第二种方式：apache HttpClient3.1

package com.powerX.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map
 Set<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.powerX.httpClient;
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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