java后台模拟浏览器发送请求

1.URLConnection方式

导入jar包

import org.springframework.web.multipart.MultipartFile;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.*;

请求工具类

public class HttpUtil {
private final static String BOUNDARY = UUID.randomUUID().toString();// 边界标识
private final static String PREFIX = "--";// 必须存在
private final static String LINE_END = "\r\n";

/**
 * 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)");
        /*设置超时时间*/
        connection.setConnectTimeout(0);
        connection.setReadTimeout(0);

        // 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
        HttpURLConnection conn = (HttpURLConnection) 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);
        /*设置超时时间*/
        conn.setConnectTimeout(0);
        conn.setReadTimeout(0);
        // 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();
        int responseCode = conn.getResponseCode();
        System.out.println("返回状态" + responseCode);
        // 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;
}

/**
 * 向指定 URL 发送POST方法的请求(带文件)
 *
 * @param url   发送请求的 URL
 * @param paramMap参数map requestFile 文件参数Map。
 * @return 所代表远程资源的响应结果
 */
public static String sendPostFile(String url, Map<String, String> paramMap, Map<String, MultipartFile> requestFile) {
    DataOutputStream out = null;
    BufferedReader in = null;
    String result = "";
    try {
        URL realUrl = new URL(url);
        // 打开和URL之间的连接
        HttpURLConnection conn = (HttpURLConnection) 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("Content-Type", "multipart/form-data;boundary=" + BOUNDARY);
        // 发送POST请求必须设置如下两行
        conn.setDoOutput(true);
        conn.setDoInput(true);
        /*设置超时时间*/
        conn.setConnectTimeout(0);
        conn.setReadTimeout(0);
        // 获取URLConnection对象对应的输出流
        out = new DataOutputStream(conn.getOutputStream());
        // 发送请求参数
        writeParams(paramMap, out);
        // flush输出流的缓冲
        out.flush();
        writeFile(requestFile, out);
        int responseCode = conn.getResponseCode();
        System.out.println("返回状态" + responseCode);
        // 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;
}

/**
 * 对post参数进行编码处理并写入数据流中
 *
 * @throws Exception
 * @throws IOException
 */
private static void writeParams(Map<String, String> requestText,
                                OutputStream os) throws Exception {
    try {
        String msg = "请求参数部分:\n";
        if (requestText == null || requestText.isEmpty()) {
            msg += "空";
        } else {
            StringBuilder requestParams = new StringBuilder();
            Set<Map.Entry<String, String>> set = requestText.entrySet();
            Iterator<Map.Entry<String, String>> it = set.iterator();
            while (it.hasNext()) {
                Map.Entry<String, String> entry = it.next();
                requestParams.append(PREFIX).append(BOUNDARY).append(LINE_END);
                requestParams.append("Content-Disposition: form-data; name=\"")
                        .append(entry.getKey()).append("\"").append(LINE_END);
                requestParams.append("Content-Type: text/plain; charset=utf-8")
                        .append(LINE_END);
                requestParams.append("Content-Transfer-Encoding: 8bit").append(
                        LINE_END);
                requestParams.append(LINE_END);// 参数头设置完以后需要两个换行，然后才是参数内容
                requestParams.append(entry.getValue());
                requestParams.append(LINE_END);
            }
            os.write(requestParams.toString().getBytes());
            os.flush();

            msg += requestParams.toString();
        }
        System.out.println(msg);
    } catch (Exception e) {
        e.printStackTrace();
        throw new Exception(e);
    }
}

/**
 * 对post上传的文件进行编码处理并写入数据流中
 *
 * @throws IOException
 */
private static void writeFile(Map<String, MultipartFile> requestFile,
                              DataOutputStream out) throws Exception {
    //文件上传
    StringBuilder fileSb = new StringBuilder();
    for (Map.Entry<String, MultipartFile> fileEntry : requestFile.entrySet()) {
        fileSb.append(PREFIX)
                .append(BOUNDARY)
                .append(LINE_END)
                /**
                 * 这里重点注意： name里面的值为服务端需要的key 只有这个key 才可以得到对应的文件
                 * filename是文件的名字，包含后缀名的 比如:abc.png
                 */
                .append("Content-Disposition: form-data; name=\"file\"; filename=\""
                        + fileEntry.getKey() + "\"" + LINE_END)
                .append("Content-Type: image/jpg" + LINE_END) //此处的ContentType不同于 请求头 中Content-Type
                .append("Content-Transfer-Encoding: 8bit" + LINE_END)
                .append(LINE_END);// 参数头设置完以后需要两个换行，然后才是参数内容
        out.writeBytes(fileSb.toString());
        out.flush();
        InputStream is = fileEntry.getValue().getInputStream();
        byte[] buffer = new byte[1024];
        int len = 0;
        while ((len = is.read(buffer)) != -1) {
            out.write(buffer, 0, len);
        }
        is.close();
        out.writeBytes(LINE_END);
    }
    //请求结束标志
    out.writeBytes(PREFIX + BOUNDARY + PREFIX + LINE_END);
    out.flush();
}

public static void main(String[] args) {
    String s = sendPost("", "");
    System.out.println(s);
}
}