Java accede a la interfaz externa de la red y obtiene datos

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import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import java.io.*;
import java.net.URL;
import java.net.URLConnection;

public class HttpRequestUtil {
    /** 日志 */
    private static Logger log = LogManager.getLogger(HttpRequestUtil.class);

    /**
     * 向指定URL发送GET方法的请求
     * 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
     * @param url
     *            发送请求的URL
     * @return URL 所代表远程资源的响应结果
     */
    public static String sendGet(String url) {
        StringBuilder result = new StringBuilder();
        BufferedReader in = null;
        try {
            URL realUrl = new URL(url);
            // 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)");
            connection.setRequestProperty("Accept-Charset", "UTF-8");
            connection.setRequestProperty("contentType", "UTF-8");
            // 建立实际的连接
            connection.connect();
            // 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(), "utf-8"));
            String line;
            while ((line = in.readLine()) != null) {
                result.append(line);
            }
        } catch (Exception e) {
//			System.out.println("发送GET请求出现异常！" + e);
            result = new StringBuilder("{\"resCode\":\"1\",\"errCode\":\"1001\",\"resData\":\"\"}");
            e.printStackTrace();
            log.error("远程服务未开启", e);
        }
        // 使用finally块来关闭输入流
        finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }

        return result.toString();
    }

    /**
     * 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;
        StringBuilder result = new StringBuilder();
        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)");
            conn.setRequestProperty("Accept-Charset", "UTF-8");
            conn.setRequestProperty("contentType", "UTF-8");
            // 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.append(line);
            }
        } catch (Exception e) {
//			System.out.println("发送 POST 请求出现异常！" + e);
            result = new StringBuilder("{\"resCode\":\"1\",\"errCode\":\"1001\",\"resData\":\"\"}");
            e.printStackTrace();
            log.error("远程服务未开启", e);
        }
        // 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.toString();
    }

    /**
     * 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 sendFile(String url, String param,
                                  BufferedInputStream bInputStream) {

        BufferedOutputStream out = null;
        BufferedReader in = null;
        StringBuilder result = new StringBuilder();
        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)");
            conn.setRequestProperty("Accept-Charset", "UTF-8");
            conn.setRequestProperty("contentType", "multipart/form-data");

            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            // 发送参数
            StringBuffer sb = new StringBuffer();
            sb = sb.append(param);
            byte[] paramData = sb.toString().getBytes();
//			System.out.println(paramData.length);

            out = new BufferedOutputStream(conn.getOutputStream());
            out.write(paramData);

            if (bInputStream != null) {
                byte[] data = new byte[2048];
                while (bInputStream.read(data) != -1) {
                    out.write(data);
                }
            }

            out.flush();
            // flush输出流的缓冲
            // 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.append(line);
            }
        } catch (Exception e) {
//			System.out.println("发送 POST 请求出现异常！" + e);
            result = new StringBuilder("{\"resCode\":\"1\",\"errCode\":\"1001\",\"resData\":\"\"}");
            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();
                }
                if (bInputStream != null) {
                    bInputStream.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        return result.toString();
    }