java 模拟http请求

整理一下用java模拟http请求的方法，如果有不正确的地方希望大家指正，如果大家有什么更好的方法欢迎提出

1、URLConnection可以向URL地址发送请求，读取URL的资源。建立和URL的连接通常需要一下几步：

  1. 创建URL对象，并通过调用openConnection方法获得URLConnection对象；
  2. 设置URLConnection参数和普通请求属性；
  3. 向远程资源发送请求；
  4. 远程资源变为可用，程序可以访问远程资源的头字段和通过输入流来读取远程资源返回的信息。
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;

public class HttpRequest {
    /**
     * 向指定URL发送GET方法的请求
     * 
     * @param url           发送请求的URL
     * @param param         请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
     * @return URL          所代表远程资源的响应结果
     */
    public static String sendGet(String url, String param) {
        String result = "";
        BufferedReader in = null;
        try {
            String urlNameString = url + "?" + param;
            URL realUrl = new URL(urlNameString);
            // 打开和URL之间的连接
            URLConnection connection = realUrl.openConnection();
            // 设置通用的请求属性
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 建立实际的连接
            connection.connect();
            // 获取所有响应头字段
            Map<String, List<String>> map = connection.getHeaderFields();
            // 遍历所有的响应头字段
            for (String key : map.keySet()) {
                System.out.println(key + "--->" + map.get(key));
            }
            // 定义 BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(
                    connection.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("发送GET请求出现异常！" + e);
            e.printStackTrace();
        }
        // 使用finally块来关闭输入流
        finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 向指定 URL 发送POST方法的请求
     * 
     * @param url          发送请求的 URL
     * @param param        请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
     * @return             所代表远程资源的响应结果
     */
    public static String sendPost(String url, String param) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            // 获取URLConnection对象对应的输出流
            out = new PrintWriter(conn.getOutputStream());
            // 发送请求参数
            out.print(param);
            // flush输出流的缓冲
            out.flush();
            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(
                    new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("发送 POST 请求出现异常！"+e);
            e.printStackTrace();
        }
        //使用finally块来关闭输出流、输入流
        finally{
            try{
                if(out!=null){
                    out.close();
                }
                if(in!=null){
                    in.close();
                }
            }
            catch(IOException ex){
                ex.printStackTrace();
            }
        }
        return result;
    }    
}

测试方法

public static void main(String[] args) {
        //发送 GET 请求
        String s=HttpRequest.sendGet("http://localhost:6144/Home/RequestString", "key=123&v=456");
        System.out.println(s);
        
        //发送 POST 请求
        String sr=HttpRequest.sendPost("http://localhost:6144/Home/RequestPostString", "key=123&v=456");
        System.out.println(sr);
 }

 参考文章 1、http://www.cnblogs.com/zhuawang/archive/2012/12/08/2809380.html

             2、http://www.cnblogs.com/ribavnu/archive/2013/05/17/3084060.html

2、HttpClient

import java.io.IOException;
import java.util.Map;

import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpException;
import org.apache.commons.httpclient.HttpMethod;
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 HttpClientTest {
    
    /**
     * @param url         发送请求的地址
     * @param params      请求参数（name=username&password=password）
     * @throws Exception
     */
    public void getMethod(String url,String params) throws Exception{
        HttpClient client = new HttpClient();
        //设置编码的问题
        client.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "utf-8");
        HttpMethod method = new GetMethod(url+"?"+params);
        //添加get请求发送的参数，如cookie等
        method.addRequestHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:39.0) Gecko/20100101 Firefox/39.0");
        
        //执行get的请求
        client.executeMethod(method);
        
        //直接得到求情返回的结果
        String result = method.getResponseBodyAsString();
        System.out.println(result);
    }
    
    /**
     * @param url         发送请求的地址
     * @param params      请求的参数 map
     * @throws HttpException
     * @throws IOException
     */
    public void postMethod(String url,Map<String,String> params) throws HttpException, IOException{
        HttpClient client = new HttpClient();
        //设置编码的问题
        client.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "utf-8");
        
        PostMethod method = new PostMethod(url);
        
        NameValuePair[] names = new NameValuePair[params!=null? params.size():0];
        int i = 0;
        if(params!=null){
            for (String key : params.keySet()) {
                names[i] = new NameValuePair(key, params.get(key));
                i++;
            }
        }
        
        //设置method的各种参数
        method.addRequestHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:39.0) Gecko/20100101 Firefox/39.0");
        method.addParameters(names);
        
        client.executeMethod(method);
        String result = method.getResponseBodyAsString();
        System.out.println(result);
    }
    
    //测试方法
    public static void main(String[] args) throws Exception {
        HttpClientTest test = new HttpClientTest();
        test.getMethod("https://www.baidu.com/", "");
    }

}



3、httpcomponents

maven导入jar包

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5</version>
</dependency>

测试类

package com.my.web;

import java.io.IOException;

import org.apache.http.HttpEntity;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
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.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;

public class Test {
　　
　　
　　 //测试方法
    public static void main(String[] args) throws ClientProtocolException, IOException {
        Test t = new Test();
        t.testPost();
        
    }
    
    
    /**
     * 测试get请求
     * @throws ParseException
     * @throws IOException
     */
    public void testGet() throws ParseException, IOException{
        CloseableHttpClient client = HttpClients.createDefault();
        HttpGet httpGet = new HttpGet("http://www.baidu.com");
        CloseableHttpResponse response = client.execute(httpGet);
        HttpEntity entity = response.getEntity();
        
        System.out.println(EntityUtils.toString(entity,"UTF-8"));
    }
    
    
    /**
     * 测试post请求
     * @throws IOException 
     * @throws ClientProtocolException 
     */
    public void testPost() throws ClientProtocolException, IOException{
        CloseableHttpClient client = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost("http://www.baidu.com");
        httpPost.setHeader(HTTP.CONTENT_TYPE, "application/x-www-form-urlencoded;charset=UTF-8");
        
        //放置参数
        StringEntity se = new StringEntity("dd=ffff","UTF-8");
        httpPost.setEntity(se);
        
        //发送请求
        CloseableHttpResponse response = client.execute(httpPost);
        HttpEntity entity = response.getEntity();
        
        System.out.println(EntityUtils.toString(entity,"UTF-8"));
    }
    
    
}

4、三种方法的比较

　　经测试第一种方法最快，第三种方法最慢，但是第一种的写法比较麻烦，所以自己偏向采用第二种方法。

　　如果在请求头中加入"User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:39.0) Gecko/20100101 Firefox/39.0"。整个方法的速度会减少2-3倍

  

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原文地址：https://www.cnblogs.com/hyzxx/p/4739924.html