使用 Java 提交 HTML 表单数据以从 jsp 应用程序中检索下载 [英] Submit HTML form data using Java to retrieve a download from a jsp application
问题描述
我有一个模糊的问题.我正在将一些 Perl 移植到 Java，并且 Perl 代码中的方法之一发布到 jsp 应用程序并下载一个 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.
I have an obscure issue. I am in the process of porting some Perl to Java and one of the methods in the Perl code posts to a jsp app and downloads a zip file. The working part of the Perl code is as follows which appears to be using a get to retrieve the file.
$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:
And the Java code I am using to try to access it:
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();
推荐答案
首先对于我在评论中发布的示例感到抱歉.我以为您只是尝试通过提交一些值来执行简单的 POST 请求.我错过了您也在上传文件.因此，由于您还上传了一个文件(请注意，您不只是在此处传递文件名)，因此这是一个 mutlipart 请求(您可以在 jsp 中看到:enctype="multipart/form-data") 并且它有更多的工作可以以编程方式完成.
First of all sorry for the example I have posted in the comment. I thought you were trying to perform a simple POST request by just submitting some values. I have missed that you were also uploading a file. So since you are also uploading a file (note that you don't just pass a filename here) this is a mutlipart request (you see that in your jsp: enctype="multipart/form-data") and it has a little more work to do that programmatically.
当您提交多部分表单时，请求如下所示:
When you are submitting a multipart form the request looks like this:
-----------------------------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--
那个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:
That strange alphanumerics are called a boundary (are chosen randomly by the browser) and are used to distringuish between submitted fields (files or normal fields). In the above example the submitted fields were:
- 一个名为myfile"的字段，它是表单中的
.用户选择了名为test.bin的文件.文件数据是单行文本Test data - 一个
按钮的"Submit"的普通字段值
- a field named "myfile" that was an
<input type="file">in the form. The user selected the file namedtest.bin. The file data was a single text lineTest data - a normal field value of
"Submit"of a<input type="submit">button
下面我从 code.java.net 上的示例，它提供了一个可以帮助您创建此类请求的类.
Below I have copied the code from an example at code.java.net that provides a class that can help you in creating such requests.
请修改任何硬编码的 url 和文件以匹配您的情况.我还没有尝试过，但它应该让你知道如何创建一个像上面那样的请求.(请注意，有两个类:一个构建请求，一个使用 main() 方法来测试它)
Please modify any hard-coded urls and files to match your case. I have not tried it out but it should give you the idea of how to create a request like the above one. (Note that there are two classes: One that constructs the request and one with a main() method to test it)
旁注:行字符
的变化不依赖于系统，但它是多部分请求构建方式的一部分.所以不管你的系统是 Windows 还是 Linux 都应该照原样使用
Side note: The change of line character
does not depend on the system but it is a part of how multipart requests are constructed. So you should use it as is no matter if your system is Windows or Linux
希望能帮到你
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 = "
";
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();
}
}
}
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