From: https://www.cnblogs.com/hhhshct/p/8523697.html
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: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;}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/x-www-form-urlencoded");// 设置鉴权信息:Authorization: Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0connection.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.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;} }
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")。