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下操作远端 url的工具包，虽然已不再更新，但实现工作中使用httpClient3.1的程式码还是很多，HttpClient4.5是org.apache.http.client下操作远端 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，话不多说上程式码。
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;// 返回结果字串
try {
// 建立远端url连线物件
URL url = new URL(httpurl);
// 通过远端url连线物件开启一个连线，强转成httpURLConnection类
connection = (HttpURLConnection) url.openConnection();
// 设定连线方式：get
connection.setRequestMethod("GET");
// 设定连线主机服务器的超时时间：15000毫秒
connection.setConnectTimeout(15000);
// 设定读取远端返回的资料时间：60000毫秒
connection.setReadTimeout(60000);
// 传送请求
connection.connect();
// 通过connection连线，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"));
// 存放资料
StringBuffer sbf = new StringBuffer();
String temp = null;
while ((temp = br.readLine()) != null) {
sbf.append(temp);
sbf.append(" ");
}
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();// 关闭远端连线
}
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);
// 通过远端url连线物件开启连线
connection = (HttpURLConnection) url.openConnection();
// 设定连线请求方式
connection.setRequestMethod("POST");
// 设定连线主机服务器超时时间：15000毫秒
connection.setConnectTimeout(15000);
// 设定读取主机服务器返回资料超时时间：60000毫秒
connection.setReadTimeout(60000);
// 预设值为：false，当向远端服务器传送资料/写资料时，需要设定为true
connection.setDoOutput(true);
// 预设值为：true，当前向远端服务读取资料时，设定为true，该引数可有可无
connection.setDoInput(true);
// 设定传入引数的格式:请求引数应该是 name1=value1&name2=value2 的形式。
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
// 设定鉴权资讯：Authorization: Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0
connection.setRequestProperty("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");
// 通过连线物件获取一个输出流
os = connection.getOutputStream();
// 通过输出流物件将引数写出去/传输出去,它是通过字节阵列写出的
os.write(param.getBytes());
// 通过连线物件获取一个输入流，向远端读取
if (connection.getResponseCode() == 200) {
is = connection.getInputStream();
// 对输入流物件进行包装:charset根据工作专案组的要求来设定
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资料
while ((temp = br.readLine()) != null) {
sbf.append(temp);
sbf.append(" ");
}
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();
}
}
// 断开与远端地址url的连线
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;
// 建立httpClient例项
HttpClient httpClient = new HttpClient();
// 设定http连线主机服务超时时间：15000毫秒
// 先获取连线管理器物件，再获取引数物件,再进行引数的赋值
httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);
// 建立一个Get方法例项物件
GetMethod getMethod = new GetMethod(url);
// 设定get请求超时为60000毫秒
getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);
// 设定请求重试机制，预设重试次数：3次，引数设定为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,打印错误资讯
System.err.println("Method faild: " + getMethod.getStatusLine());
} else {
// 通过getMethod例项，获取远端的一个输入流
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(" ");
}
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();
}
}
// 释放连线
getMethod.releaseConnection();
}
return result;
}
public static String doPost(String url, Map paramMap) {
// 获取输入流
InputStream is = null;
BufferedReader br = null;
String result = null;
// 建立httpClient例项物件
HttpClient httpClient = new HttpClient();
// 设定httpClient连线主机服务器超时时间：15000毫秒
httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);
// 建立post请求方法例项物件
PostMethod postMethod = new PostMethod(url);
// 设定post请求超时时间
postMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);
NameValuePair[] nvp = null;
// 判断引数map集合paramMap是否为空
if (null != paramMap && paramMap.size() > 0) {// 不为空
// 建立键值引数物件阵列，大小为引数的个数
nvp = new NameValuePair[paramMap.size()];
// 循环遍历引数集合map
Set> entrySet = paramMap.entrySet();
// 获取迭代器
Iterator> iterator = entrySet.iterator();
int index = 0;
while (iterator.hasNext()) {
Entry mapEntry = iterator.next();
// 从mapEntry中获取key和value建立键值物件存放到阵列中
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阵列是否为空
if (null != nvp && nvp.length > 0) {
// 将引数存放到requestBody物件中
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());
}
// 获取远端返回的资料
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(" ");
}
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();
}
}
// 释放连线
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 {
// 通过址预设配置建立一个httpClient例项
httpClient = HttpClients.createDefault();
// 建立httpGet远端连线例项
HttpGet httpGet = new HttpGet(url);
// 设定请求头资讯，鉴权
httpGet.setHeader("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");
// 设定配置请求引数
RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(35000)// 连线主机服务超时时间
.setConnectionRequestTimeout(35000)// 请求超时时间
.setSocketTimeout(60000)// 资料读取超时时间
.build();
// 为httpGet例项设定配置
httpGet.setConfig(requestConfig);
// 执行get请求得到返回物件
response = httpClient.execute(httpGet);
// 通过返回物件获取返回资料
HttpEntity entity = response.getEntity();
// 通过EntityUtils中的toString方法将结果转换为字串
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 paramMap) {
CloseableHttpClient httpClient = null;
CloseableHttpResponse httpResponse = null;
String result = "";
// 建立httpClient例项
httpClient = HttpClients.createDefault();
// 建立httpPost远端连线例项
HttpPost httpPost = new HttpPost(url);
// 配置请求引数例项
RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(35000)// 设定连线主机服务超时时间
.setConnectionRequestTimeout(35000)// 设定连线请求超时时间
.setSocketTimeout(60000)// 设定读取资料连线超时时间
.build();
// 为httpPost例项设定配置
httpPost.setConfig(requestConfig);
// 设定请求头
httpPost.addHeader("Content-Type", "application/x-www-form-urlencoded");
// 封装post请求引数
if (null != paramMap && paramMap.size() > 0) {
List nvps = new ArrayList();
// 通过map整合entrySet方法获取entity
Set> entrySet = paramMap.entrySet();
// 循环遍历，获取迭代器
Iterator> iterator = entrySet.iterator();
while (iterator.hasNext()) {
Entry mapEntry = iterator.next();
nvps.add(new BasicNameValuePair(mapEntry.getKey(), mapEntry.getValue().toString()));
}
// 为httpPost设定封装好的请求引数
try {
httpPost.setEntity(new UrlEncodedFormEntity(nvps, "UTF-8"));
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
try {
// httpClient物件执行post请求,并返回响应引数物件
httpResponse = httpClient.execute(httpPost);
// 从响应物件中获取响应内容
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，可能传入的引数是json或者其他格式，此时我们则需要更改请求头及引数的设定资讯，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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