java 实现HTTP请求

最新推荐文章于 2025-05-17 14:43:21 发布

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最新推荐文章于 2025-05-17 14:43:21 发布

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分类专栏：随笔文章标签： java

本文链接：https://blog.youkuaiyun.com/u013890024/article/details/53509378

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本文介绍了一种处理HTTP请求的方法，包括GET和POST请求的发送，并展示了如何配置请求头信息以实现有效的网络通信。此外，还提供了通过HTTP请求下载图片文件的具体实现。

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http请求：

    private static final int DEFAULT_TIMEOUT = 5000;
    private static final String Accept = "application/json,text/html, */*; q=0.01";
    private static final String Accept_Encoding = "deflate";
    private static final String Accept_Language = "zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3";
    private static final String Connection = "keep-alive";
    private static final String Content_Type = "application/x-www-form-urlencoded; charset=UTF-8";
    private static final String User_Agent = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36";
    private static final String X_Requested_With= "XMLHttpRequest";
    public static final String HTTP_GET_METHOD = "GET";
    public static final String HTTP_POST_METHOD = "POST";

    public static void send(String url, String param,Map<String,Object> maps,String type) {
        Map<String,Object> resultMap=new HashMap<String, Object>();
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            if(type.toUpperCase().equals("GET")){
                url=url + "?" + param;
            }
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection conns = realUrl.openConnection();
            HttpURLConnection conn = (HttpURLConnection) conns;
            //解决302请求直接重定向响应头信息中的location页面
            conn.setInstanceFollowRedirects(false);
            // 设置通用的请求属性
            conn.setRequestProperty("Accept", Accept);
            conn.setRequestProperty("Accept-Encoding", Accept_Encoding);          
            conn.setRequestProperty("Accept-Language", Accept_Language);
            conn.setRequestProperty("Connection", Connection);
            conn.setRequestProperty("Content-Type", Content_Type);
            conn.setRequestProperty("User-Agent", User_Agent);
            conn.setRequestProperty("X-Requested-With",X_Requested_With);
            conn.setConnectTimeout(DEFAULT_TIMEOUT);        
            conn.setUseCaches(false); 
            if(type.toUpperCase().equals("POST")){
                conn.setRequestMethod("POST");
                // 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 conn.getOutputStream()会默认调用connection.connect() 所以不用写
                out = new PrintWriter(conn.getOutputStream());
                // 发送请求参数
                out.print(param);
                // flush输出流的缓冲
                out.flush();
            }else{
                conn.setRequestMethod("GET");
                // 建立实际的连接
                conn.connect();
            }
            //判断请求状态码
           int status= conn.getResponseCode();
           //
           if(status==302){         
               //如果会重定向，保存302重定向地址    
           }
            // 获取所有响应头字段
            Map<String, List<String>> map = conn.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(
                    conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }

        } catch (Exception e) {
            loger.info("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(out!=null){
                    out.close();
                }
                if(in!=null){
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
    }

http请求获取图片文件等信息时，建立连接后的代码：

        byte[] data = new byte[1024];
         int len = 0;
         FileOutputStream fileOutputStream = null;
         InputStream inputStream = null;
         inputStream = conn.getInputStream();
         try {
             HttpServletRequest request= ServletActionContext.getRequest();
             fileOutputStream = new FileOutputStream(request.getSession().getServletContext().getRealPath("")+"\\images\\loginCode.jpg");
             while ((len = inputStream.read(data)) != -1) {
                 fileOutputStream.write(data, 0, len);
             }
             return true;
         } catch (IOException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
             return false;
         }