JEE上傳文件的IO流

OYM的任務中，有個要求，上傳一個Excel文件，檢查他的內容是否合法，並返回信息。

今天想了一下，第一個要解決的問題就是上傳一個Excel文件，上傳文件的組件到挺多的，網上一搜，就有一大堆教程，但是現在並不是要上傳一個文件到服務器以作存儲之用，而是要上傳一個文件到內存裏，以Java的數據結構存儲起來，並檢查，把合乎要求的數據寫到數據庫裏。所以在網上的一大堆上傳文件的組件並不合用。於是又想自己寫，思路就是從客戶端那裏獲取一個InputStream，然後就對這個InputStream做一系列的檢查。代碼如下：

ServletInputStream sis =  request.getInputStream();
InputStreamReader isr = new InputStreamReader(sis);
             
int ch;
while((ch = isr.read()) != -1 ) {          
   out.println((char)ch);
}
             
System.out.flush();

結果的出去就是如下（輸出東西寫到頁面）：

-----------------------------7d7ea23120550 
Content-Disposition: form-data; name="file1"; 
filename="C:\Documents and Settings\Administrator\桌面\test.txt" 
Content-Type: text/plain 
my name is Rokey.Ｒｏｋｅｙ。我的名字叫Rokey. 
-----------------------------7d7ea23120550 Content-Disposition: form-data; 
name="Submit" 上傳 -----------------------------7d7ea23120550--

很明顯，這裏只有

my name is Rokey.Ｒｏｋｅｙ。我的名字叫Rokey.

對我有用，這個也正是我的文件裏面的內容，其它的都是關於這些form的其它信息。對我這個程序是沒有用的。如果這裏寫下去的話，還要我去分析那些是數據，哪些是form的參數。好，到現在爲止，我已經打消了自己寫的念頭了。我想，那些組件都可以把上傳文件封裝得那麼好，能不能利用那些庫，抽出文件的IO流，讓我操作呢?

於是，就開始對O'Reilly的上傳組件cos.jar的API看，看到裏面有這麼一段。

public class MultipartParser
extends java.lang.Object
A utility class to handle multipart/form-data requests, the kind of requests that support file uploads. This class uses a "pull" model where the reading of incoming files and parameters is controlled by the client code, which allows incoming files to be stored into any OutputStream. If you wish to use an API which resembles HttpServletRequest, use the "push" model MultipartRequest instead. It's an easy-to-use wrapper around this class.

This class can receive arbitrarily large files (up to an artificial limit you can set), and fairly efficiently too. It cannot handle nested data (multipart content within multipart content). It can now with the latest release handle internationalized content (such as non Latin-1 filenames).

It also optionally includes enhanced buffering and Content-Length limitation. Buffering is only required if your servlet container is poorly implemented (many are, including Tomcat 3.2), but it is generally recommended because it will make a slow servlet container a lot faster, and will only make a fast servlet container a little slower. Content-Length limiting is usually only required if you find that your servlet is hanging trying to read the input stram from the POST, and it is similarly recommended because it only has a minimal impact on performance.

而且裏面的API已經封裝程我想象得到的情況了。於是，我就覺得這樣我就可以完成我的功能了。於是，就寫了以下代碼：

MultipartParser mp = new MultipartParser(request, 10 * 1024 * 1024);
Part part;
while ((part = mp.readNextPart()) != null) {
      if (part.isParam()) {
          // it's a parameter part
          ParamPart paramPart = (ParamPart) part;
          //out.println("param: name=" + name + "; value=" + value);
      } else if (part.isFile()) {
          FilePart filePart = (FilePart) part;
          InputStream is = filePart.getInputStream();
          InputStreamReader isr = new InputStreamReader(is);

          int ch;
          while ((ch = isr.read()) != -1) {

              out.print((char) ch);
          }

          System.out.flush();
          isr.close();
          is.close();
      }
}
               

出去結果如下：

my name is Rokey.Ｒｏｋｅｙ。
我的名字叫Rokey.

到現在，已經可以把這個流封裝成一個文件流，送給Excel的組件去處理了。