HTTP传输协议，包括HttpUrlConnection和HttpClient。

HTTP说明：
1、无连接，一次处理一个请求
2、无状态，对于请求处理没有记忆能力
3、应用层的协议，底层为socket协议，TCP

HTTP请求：

//请求行 

GET /test HTTP/ (CRLF)

//消息报头

Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
Accept-Encoding:gzip, deflate, br
Accept-Language:zh-CN,zh;q=0.8,en;q=0.6
Connection:keep-alive
Host:127.0.0.1:8080
Upgrade-Insecure-Requests:1
User-Agent:Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.115 Safari/537.36

//请求正文 

user=jeffrey&pwd=1234

HTTP响应：

//状态行 

HTTP/1.1 200 OK (CRLF)

//消息报头

Cache-Control:no-cache
Content-Type:application/json;charset=UTF-8
Date:Tue, 11 Jul 2017 06:07:43 GMT
Expires:Thu, 01 Jan 1970 00:00:00 GMT
Pragma:no-cache
Server:Apache-Coyote/1.1
Transfer-Encoding:chunked

//响应正文

{"RetMsg":"请求报文为空","RetCode":"9998"}

关于请求参数乱码问题：

1、设置相关字符集，包括服务端tomcat字符集

请求参数特殊字符被转换：

1、URLHttpConnection的GET和POST都会有这个问题

2、HttpClient的GET有这个问题，POST没有这个问题

3、在请求或者接收报文是，对特殊字符做相应的替换操作。例如，在报文值中要传递+，可先将+转换为%2B，再传输

项目结构：

package com.utils;import java.io.BufferedReader;import java.io.DataOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import java.util.HashMap;import java.util.Map;public class HttpUrl {private static final String CHARSET = "utf-8";private static final int TIMEOUT = 10*1000;/** * HttpUrlConnection * jdk自带 *  * 注意： * 1、字符集设置 * 2、请求报文值有+等特殊字符，服务端获取时转换成了空格，如何处理？ *//** * get请求，请求参数放在url后面 * @param urlPath * @return */public static String doGet(String urlPath){try {System.out.println("请求地址："+urlPath);URL url = new URL(urlPath);HttpURLConnection connect = (HttpURLConnection) url.openConnection();connect.setInstanceFollowRedirects(false); // 禁止自动重定向跳转，302重定向响应码connect.setConnectTimeout(TIMEOUT); // 连接超时时间，毫秒，默认不会超时connect.setReadTimeout(TIMEOUT); // 传递数据超时时间，毫秒，默认不会超时// 获取响应码和响应信息int responseCode = connect.getResponseCode();String responseMsg = connect.getResponseMessage();System.out.println("【状态码："+responseCode+"，状态信息："+responseMsg+"】");if(responseCode!=HttpURLConnection.HTTP_OK){return null;}// 获取响应消息体InputStream is = connect.getInputStream();BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is, CHARSET));StringBuffer sb = new StringBuffer();String readLine = null;while((readLine=bufferedReader.readLine())!=null){sb.append(readLine);}is.close();bufferedReader.close();connect.disconnect();System.out.println("返回报文："+sb.toString());return sb.toString();} catch (MalformedURLException e) {e.printStackTrace();System.out.println("创建链接失败");return null;} catch (IOException e) {e.printStackTrace();System.out.println("打开链接失败");return null;}}/** * post请求，参数以流的形式写出，返回报文以流的形式读取 * @param urlPath * @param params * @return */public static String doPost(String urlPath, Map<String, Object> params){try {System.out.println("请求地址："+urlPath);URL url = new URL(urlPath);HttpURLConnection connect = (HttpURLConnection) url.openConnection(); // 生成一个连接对象connect.setDoInput(true); // 允许输入，默认trueconnect.setDoOutput(true); // 允许输出，默认false。正好说明了post请求需要用流的形式写出参数connect.setRequestMethod("POST"); // 设置请求类型，默认为getconnect.setUseCaches(false); // 禁用缓存connect.setInstanceFollowRedirects(false); // 禁止自动重定向跳转，302重定向响应码connect.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); // 报文类型，MIME，已表单键值对格式提交connect.setConnectTimeout(TIMEOUT); // 连接超时时间，毫秒，默认不会超时connect.setReadTimeout(TIMEOUT); // 传递数据超时时间，毫秒，默认不会超时connect.connect(); // 打开连接DataOutputStream out = new DataOutputStream(connect.getOutputStream());StringBuffer sb = new StringBuffer();if(params!=null){for(String key : params.keySet()){sb.append(key + "=" + params.get(key) +"&");}}String content = sb.length()==0?"":sb.substring(0, sb.length()-1);System.out.println("请求报文："+content);out.write(content.getBytes(CHARSET)); // 注意此处的字符集设置out.flush();out.close();// 获取响应码和响应信息int responseCode = connect.getResponseCode();String responseMsg = connect.getResponseMessage();System.out.println("【状态码："+responseCode+"，状态信息："+responseMsg+"】");if(responseCode!=HttpURLConnection.HTTP_OK){return null;}// 获取响应消息体InputStream in = connect.getInputStream();BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in, CHARSET));StringBuffer sb_1 = new StringBuffer();String readLine = null;while((readLine=bufferedReader.readLine())!=null){sb_1.append(readLine);}in.close();bufferedReader.close();connect.disconnect();System.out.println("返回报文："+sb_1.toString());return sb_1.toString();} catch (MalformedURLException e) {e.printStackTrace();System.out.println("创建链接失败");return null;} catch (IOException e) {e.printStackTrace();System.out.println("打开链接失败");return null;}}public static void main(String[] args) {long timeBegin = System.currentTimeMillis();System.out.println(timeBegin);Map<String, Object> params = new HashMap<String, Object>();params.put("name", "周星星");params.put("wife", "zixia");HttpUrl.doPost("http://127.0.0.1:8080/olt/org/test", params);//HttpUrl.doGet("http://127.0.0.1:8080/olt/org/test?a=1&b=周星星");long timeEnd = System.currentTimeMillis();System.out.println(timeEnd);System.out.println("耗时："+(timeEnd-timeBegin));}}

package com.test;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import org.apache.http.HttpEntity;import org.apache.http.NameValuePair;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;public class HttpClientTest {private static final int TIMEOUT = 10*1000; // 60sprivate static final String CHARSET = "utf-8";/** * get请求，相关配置通过RequestConfig配置 * @param urlPath * @return */public static String doGet(String urlPath){System.out.println("请求地址："+urlPath);HttpGet httpGet = new HttpGet(urlPath);//HttpClient hc = new DefaultHttpClient(); // 过时了CloseableHttpClient httpClient = HttpClients.createDefault();try {RequestConfig config = RequestConfig.custom().setConnectTimeout(TIMEOUT).setSocketTimeout(TIMEOUT) // read time out.build();httpGet.setConfig(config); // 相关配置CloseableHttpResponse httpResponse = httpClient.execute(httpGet);int responseCode = httpResponse.getStatusLine().getStatusCode();System.out.println("【状态码："+responseCode+"】");HttpEntity httpEntity = httpResponse.getEntity();InputStream in = httpEntity.getContent();BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in, CHARSET));StringBuffer sb = new StringBuffer();String readLine = null;while((readLine=bufferedReader.readLine())!=null){sb.append(readLine);}in.close();bufferedReader.close();httpClient.close();System.out.println("返回报文："+sb.toString());return sb.toString();} catch (IOException e) {e.printStackTrace();System.out.println("创建连接异常");return null;}}/** * POST请求 * @param urlPath * @param params * @return */public static String doPost(String urlPath, Map<String, Object> params){System.out.println("请求地址："+urlPath);HttpPost httpPost = new HttpPost(urlPath);CloseableHttpClient httpClient = HttpClients.createDefault();// 请求参数List<NameValuePair> urlParams = new ArrayList<NameValuePair>();if(params!=null){for(String key : params.keySet()){urlParams.add(new BasicNameValuePair(key, params.get(key)+""));}}try {HttpEntity httpEntity = new UrlEncodedFormEntity(urlParams, CHARSET); // 设置字符集httpPost.setEntity(httpEntity);RequestConfig config = RequestConfig.custom().setConnectTimeout(TIMEOUT).setSocketTimeout(TIMEOUT) // read time out.build();httpPost.setConfig(config); // 请求配置CloseableHttpResponse httpResponse = httpClient.execute(httpPost);int responseCode = httpResponse.getStatusLine().getStatusCode();System.out.println("【状态码："+responseCode+"】");InputStream in = httpEntity.getContent();BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in));StringBuffer sb = new StringBuffer();String readLine = null;while((readLine=bufferedReader.readLine())!=null){sb.append(readLine);}System.out.println("返回报文："+sb.toString());return sb.toString();} catch (Exception e) {e.printStackTrace();System.out.println("请求异常");return null;}}public static void main(String[] args) {long timeBegin = System.currentTimeMillis();System.out.println(timeBegin);Map<String, Object> params = new HashMap<String, Object>();params.put("name", "周星星");params.put("wife", "zixia");HttpClientTest.doPost("http://127.0.0.1:8080/olt/org/test", params);//HttpClientTest.doGet("http://127.0.0.1:8080/olt/org/test?name=周星星&wift=zixia");long timeEnd = System.currentTimeMillis();System.out.println(timeEnd);System.out.println("耗时："+(timeEnd-timeBegin));}}