1

我正在尝试构建一个解析表单输入并从中创建 .csv 文件的 servlet，但是 bufferedWriter 对象无缘无故（对我来说显然）截断了很多字符。

        String filepath = getServletContext().getRealPath("\\") + "temp";
        String filename = "csv"+dateFormat.format(date)+".csv";
        File file = new File(filepath + filename);            
        file.createNewFile();
        BufferedWriter fwrite = new BufferedWriter(new FileWriter(file));
        for(int i=0; i<list.size(); i++) {
            String[] dataEntry = list.get(i);
            for (int j=0; j<dataEntry.length;j++)                 
                 fwrite.write("test1-2");
                //fwrite.append(dataEntry[j]+";");     
            fwrite.newLine();
        }
        fwrite.close();            
         URI fileUri = file.toURI();
         stream = response.getOutputStream();
         response.setContentType("text/csv");
         response.addHeader("Content-Disposition", "attachment; filename="
            + filename);

         URLConnection urlConn = fileUri.toURL().openConnection();
         response.setContentLength((int) urlConn.getContentLength());
         buf = new  BufferedInputStream(urlConn.getInputStream());                          
         while (buf.read() != -1)
            stream.write(buf.read());
        } finally {
        if (stream != null)
            stream.close();
        if (buf != null)
            buf.close();     
        }          
}

对不起，如果代码有点草率。我在为每个条目编写“test1-2”字符串时的当前输出是

et-ts12et-ts12et-ts12ÿ

对代码本身的任何进一步评论将不胜感激我只是在尝试我在网上找到的东西，我没有实际的最佳实践参考点。

4

1 回答 1

1

我可能会添加一些方法，以免单个方法过大。例如：

/**
 * Saves the List of String[] to the File.
 * 
 * @param f
 * @param list
 * 
 * @throws IOException
 */
void saveList(File f, List<String[]> list) throws IOException {
    FileWriter fw = null;
    try {
        fw = new FileWriter(f);
        saveList(fw, list);
    } finally {
        if (null != fw) {
            // Ensure that fw is closed.
            fw.close();
        }
    }
}

/**
 * Saves the List of String[] to the Writer.
 * 
 * @param w
 * @param list
 * 
 * @throws IOException
 */
void saveList(Writer w, List<String[]> list) throws IOException {
    BufferedWriter bw = new BufferedWriter(w);
    for (int i = 0; i < list.size(); i++) {
        String[] dataEntry = list.get(i);
        for (int j = 0; j < dataEntry.length; j++) {
            bw.write("test1-2");
            // bw.append(dataEntry[j]+";");
        }
        bw.newLine();
    }
    bw.flush();
}

/**
 * Copies in's contents to out.
 * 
 * @param in
 *            Must not be null.
 * @param out
 *            Must not be null.
 * 
 * @throws IOException
 */
void copyStream(InputStream in, OutputStream out) throws IOException {
    if (null == in) {
        throw new NullPointerException("in must not be null");
    }
    if (null == out) {
        throw new NullPointerException("out must not be null");
    }
    byte[] buf = new byte[1024 * 8];
    int read = -1;
    while ((read = in.read(buf)) > -1) {
        out.write(buf, 0, read);
    }
}

/**
 * Copies in's contents to out, and ensures that in is closed afterwards.
 * 
 * @param in
 *            Must not be null.
 * @param out
 *            Must not be null.
 * 
 * @throws IOException
 */
void copyStreamAndCloseIn(InputStream in, OutputStream out) throws IOException {
    try {
        copyStream(in, out);
    } finally {
        in.close();
    }
}

public void service(HttpServletRequest request, HttpServletResponse response) throws IOException {
    String filepath = getServletContext().getRealPath("\\") + "temp";
    String filename = "csv" + dateFormat.format(date) + ".csv";
    File file = new File(filepath + filename);
    file.createNewFile();

    saveList(file, list);

    long length = file.length();
    response.setContentType("text/csv");
    response.addHeader("Content-Disposition", "attachment; filename=" + filename);
    response.setContentLength((int) length);

    copyStreamAndCloseIn(new FileInputStream(file), response.getOutputStream());
}

至于奇怪的输出et-ts12et-ts12et-ts12ÿ，我不确定为什么会这样。

你如何看待这个价值？打印到控制台，然后读取文件？根据使用的字符编码，打印到控制台和在另一个编辑器中打开文件都可能产生奇怪的结果。

于 2012-02-20T17:57:39.997 回答