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java - 使用 Java 提交 HTML 表单数据以检索 jsp 应用程序的下载

转载 作者：行者123 更新时间：2023-12-01 14:15:22 24 4
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我有一个模糊的问题。我正在将一些 Perl 移植到 Java，Perl 代码中的方法之一发布到 jsp 应用程序并下载 zip 文件。 Perl 代码的工作部分如下所示，它似乎使用 get 来检索文件。

$mech->get ( $url );
$mech->submit_form(
fields => {
     upload => variable1,
     selectValue => variable2,
    },
);

jsp页面如下:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Extract Features</title>
</head>

<body>
<form action="extract.zip" method="post" enctype="multipart/form-data">
<table>
<tr>
    <th align="left">File:</th>
    <td><input type="file" name="upload"></td>
</tr>
<tr>
    <th align="left">Code:</th>
    <td><select name="selectValue">
        <option value="13" selected="selected">13</option>
        <option value="14">14</option>
        <option value="15">15</option>
    </select></td>
</tr>

<tr>
    <td align="center" colspan="2"><input type="submit" value="Submit"></td>
</tr>
</table>
</form>
</body>
</html>

以及我用来尝试访问它的 Java 代码:

URL url = new URL(s.getUrlScheme(), s.getUrlHost(), s.getUrlFile());
String urlParameters = "upload=C:\\testFile.txt&selectValue=14";
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
connection.setDoInput(true);
connection.setDoOutput(true);
connection.setInstanceFollowRedirects(false);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", "text/html");
connection.setRequestProperty("charset", "ISO-8859-1");
connection.setRequestProperty("Content-Length", Integer.toString(urlParameters.length()));
connection.setUseCaches(false);
DataOutputStream wr = new DataOutputStream(connection.getOutputStream());
wr.writeBytes(urlParameters);
wr.flush();
wr.close();
InputStream is = connection.getInputStream();
OutputStream os = new FileOutputStream(".\\test.html");

int data;
while ((data=is.read()) != -1) {
os.write(data);
}

is.close();
os.close();
connection.disconnect();

最佳答案

首先对我在评论中发布的示例表示歉意。我以为您正在尝试通过提交一些值来执行简单的 POST 请求。我没有注意到您还上传了文件。因此，由于您还要上传一个文件(请注意，您不只是在此处传递文件名)，这是一个多部分请求(您在 jsp: enctype="multipart/form-data" 中看到了这一点)并且它还有更多的工作以编程方式执行此操作。

当您提交多部分表单时，请求如下所示:

-----------------------------253171262814565
Content-Disposition: form-data; name="myfile"; filename="test.bin"
Content-Type: application/octet-stream

Test data    
-----------------------------253171262814565
Content-Disposition: form-data; name="submit"

Submit
-----------------------------253171262814565--

这种奇怪的字母数字被称为边界(由浏览器随机选择)，用于区分提交的字段(文件或普通字段)。在上面的例子中，提交的字段是:

  • 名为“myfile”的字段，它是表单中的 <input type="file">。用户选择了名为 test.bin 的文件。文件数据是单个文本行 Test data
  • "Submit" 按钮的 <input type="submit"> 的正常字段值

下面我复制了 an example at code.java.net 中的代码，该代码提供了一个可以帮助您创建此类请求的类。

请修改所有硬编码的网址和文件以符合您的情况。我还没有尝试过，但它应该能让您了解如何创建像上面这样的请求。 (请注意，有两个类:一个用于构造请求，另一个使用 main() 方法来测试它)

旁注:行字符 \r\n 的更改不依赖于系统，但它是多部分请求构造方式的一部分。因此，无论您的系统是 Windows 还是 Linux，您都应该按原样使用它

希望有帮助

package net.codejava.networking;

import java.io.BufferedReader;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;

/**
 * This utility class provides an abstraction layer for sending multipart HTTP
 * POST requests to a web server.
 * @author www.codejava.net
 *
 */
public class MultipartUtility {
    private final String boundary;
    private static final String LINE_FEED = "\r\n";
    private HttpURLConnection httpConn;
    private String charset;
    private OutputStream outputStream;
    private PrintWriter writer;

    /**
     * This constructor initializes a new HTTP POST request with content type
     * is set to multipart/form-data
     * @param requestURL
     * @param charset
     * @throws IOException
     */
    public MultipartUtility(String requestURL, String charset)
            throws IOException {
        this.charset = charset;

        // creates a unique boundary based on time stamp
        boundary = "===" + System.currentTimeMillis() + "===";

        URL url = new URL(requestURL);
        httpConn = (HttpURLConnection) url.openConnection();
        httpConn.setDoOutput(true); // indicates POST method
        httpConn.setDoInput(true);
        httpConn.setRequestProperty("Content-Type",
                "multipart/form-data; boundary=" + boundary);
        outputStream = httpConn.getOutputStream();
        writer = new PrintWriter(new OutputStreamWriter(outputStream, charset),
                true);
    }

    /**
     * Adds a form field to the request
     * @param name field name
     * @param value field value
     */
    public void addFormField(String name, String value) {
        writer.append("--" + boundary).append(LINE_FEED);
        writer.append("Content-Disposition: form-data; name=\"" + name + "\"")
                .append(LINE_FEED);
        writer.append("Content-Type: text/plain; charset=" + charset).append(
                LINE_FEED);
        writer.append(LINE_FEED);
        writer.append(value).append(LINE_FEED);
        writer.flush();
    }

    /**
     * Adds a upload file section to the request
     * @param fieldName name attribute in <input type="file" name="..." />
     * @param uploadFile a File to be uploaded
     * @throws IOException
     */
    public void addFilePart(String fieldName, File uploadFile)
            throws IOException {
        String fileName = uploadFile.getName();
        writer.append("--" + boundary).append(LINE_FEED);
        writer.append(
                "Content-Disposition: form-data; name=\"" + fieldName
                        + "\"; filename=\"" + fileName + "\"")
                .append(LINE_FEED);
        writer.append(
                "Content-Type: "
                        + URLConnection.guessContentTypeFromName(fileName))
                .append(LINE_FEED);
        writer.append("Content-Transfer-Encoding: binary").append(LINE_FEED);
        writer.append(LINE_FEED);
        writer.flush();

        FileInputStream inputStream = new FileInputStream(uploadFile);
        byte[] buffer = new byte[4096];
        int bytesRead = -1;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, bytesRead);
        }
        outputStream.flush();
        inputStream.close();

        writer.append(LINE_FEED);
        writer.flush();    
    }

    /**
     * Completes the request and receives response from the server.
     * @return a list of Strings as response in case the server returned
     * status OK, otherwise an exception is thrown.
     * @throws IOException
     */
    public List<String> finish() throws IOException {
        List<String> response = new ArrayList<String>();

        writer.append(LINE_FEED).flush();
        writer.append("--" + boundary + "--").append(LINE_FEED);
        writer.close();

        // checks server's status code first
        int status = httpConn.getResponseCode();
        if (status == HttpURLConnection.HTTP_OK) {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    httpConn.getInputStream()));
            String line = null;
            while ((line = reader.readLine()) != null) {
                response.add(line);
            }
            reader.close();
            httpConn.disconnect();
        } else {
            throw new IOException("Server returned non-OK status: " + status);
        }

        return response;
    }
}

//---------------------------------------------------------

package net.codejava.networking;

import java.io.File;
import java.io.IOException;
import java.util.List;

/**
 * This program demonstrates a usage of the MultipartUtility class.
 * @author www.codejava.net
 *
 */
public class MultipartFileUploader {

    public static void main(String[] args) {
        String charset = "UTF-8";
        File uploadFile1 = new File("e:/Test/PIC1.JPG");
        File uploadFile2 = new File("e:/Test/PIC2.JPG");
        String requestURL = "http://localhost:8080/FileUploadSpringMVC/uploadFile.do";

        try {
            MultipartUtility multipart = new MultipartUtility(requestURL, charset);
            multipart.addFormField("description", "Cool pix");
            multipart.addFilePart("fileUpload", uploadFile1);
            multipart.addFilePart("fileUpload", uploadFile2);

            List<String> response = multipart.finish();
            System.out.println("SERVER REPLIED:");
            for (String line : response) {
                System.out.println(line);
            }
        } catch (IOException ex) {
            System.out.println("ERROR: " + ex.getMessage());
            ex.printStackTrace();
        }
    }
}

关于java - 使用 Java 提交 HTML 表单数据以检索 jsp 应用程序的下载，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/18153691/

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