通过HttpServletResponse对象，实现图片的流方式显示和文件的流方式下载

1.图片的流方式显示，在controller中创建以下方法：

public void showImage(HttpServletRequest request, HttpServletResponse response) throws Exception {
    response.setContentType("image/jpeg");  
    // 获取图片
    File file = new File("/home/aaa.jpg");  
    // 创建文件输入流  
    FileInputStream is = new FileInputStream(file);  
    // 响应输出流  
    ServletOutputStream out = response.getOutputStream();  
    // 创建缓冲区  
    byte[] buffer = new byte[1024];  
    int len = 0;  
    while ((len = is.read(buffer)) != -1) {  
        out.write(buffer, 0, len);  
    }  
    is.close();  
    out.flush();  
    out.close();
}

页面展示图片的时候，直接在img标签的src属性中调用这个方法：

<img src="/.../showImage.ht" />

2.文件的流方式下载：

public void download(File file, String fileName, HttpServletResponse response) throws IOException{
    if(null != file){
        OutputStream out =null;
        InputStream in = null;
        try{
            in = new BufferedInputStream(new FileInputStream(file));
            byte[] buffer = new byte[in.available()];
            in.read(buffer);
            response.reset();
            response.setHeader("content-disposition","attachment;filename=" + encodingFileName(fileName));   
            out = new BufferedOutputStream(response.getOutputStream());
            out.write(buffer);
        }catch(IOException e){
            e.printStackTrace();
        }finally{
            if(null != in){
                in.close();
            }
            if(null != out){
                out.close();
            }
        }
    }
}

//对文件名进行编码，解决下载文件名中文乱码的问题
private static String encodingFileName(String fileName) {
    String returnFileName = "";
    try {
        returnFileName = URLEncoder.encode(fileName, "UTF-8");
        returnFileName = StringUtils.replace(returnFileName, "+", "%20");
        if (returnFileName.length() > 150) {
            returnFileName = new String(fileName.getBytes("GB2312"), "ISO8859-1");
            returnFileName = StringUtils.replace(returnFileName, " ", "%20");
        }
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }
    return returnFileName;
}