怎样实现下载?

Question

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Answer 1

public void downloadFile(String sourceFilePathName, String contentType, String destFileName,
                             int blockSize) throws IOException, ServletException{
        if(sourceFilePathName == null)
            throw new IllegalArgumentException("File '"+sourceFilePathName+"' not found.");
        if(sourceFilePathName.equals(""))
            throw new IllegalArgumentException("File '"+sourceFilePathName+"' not found.");
        if(isVirtual(sourceFilePathName))
            sourceFilePathName = m_application.getRealPath(sourceFilePathName);
        File file = new File(sourceFilePathName);
        if(!file.exists())
            throw new IllegalArgumentException("File '"+sourceFilePathName+"' not found.");        FileInputStream fileIn = new FileInputStream(file);
        long fileLen = file.length();
        int readBytes = 0;
        int totalRead = 0;
        byte b[] = new byte[blockSize];
        if(contentType == null)
            m_response.setContentType(downContentType);
        else
        if(contentType.length() == 0)
            m_response.setContentType(downContentType);
        else
            m_response.setContentType(contentType);
        m_response.setContentLength((int)fileLen);        m_contentDisposition = m_contentDisposition != null ? m_contentDisposition : "attachment;";
        if(destFileName == null)
            m_response.setHeader("Content-Disposition", m_contentDisposition+" filename="+getFileName(sourceFilePathName));
        else
        if(destFileName.length() == 0)
            m_response.setHeader("Content-Disposition", m_contentDisposition);
        else
            m_response.setHeader("Content-Disposition", m_contentDisposition+" filename="+destFileName);
        while((long)totalRead < fileLen){
            readBytes = fileIn.read(b, 0, blockSize);
            totalRead += readBytes;
            m_response.getOutputStream().write(b, 0, readBytes);
        }
        fileIn.close();
    }

Answer 2

zip,rar文件可以用第一种方法简单。
txt,doc,...就得用后一种方法啦。