Spring中实现文件上传
详见:http://blog.yemou.net/article/query/info/tytfjhfascvhzxcyt110
实现图片上传
用户必须能够上传图片,因此需要文件上传的功能。比较常见的文件上传组件有Commons FileUpload(http://jakarta.apache.org/commons/fileupload/a>)和COS FileUpload(http://www.servlets.com/cos),Spring已经完全集成了这两种组件,这里我们选择Commons FileUpload。
由于Post一个包含文件上传的Form会以multipart/form-data请求发送给服务器,必须明确告诉DispatcherServlet如何处理MultipartRequest。首先在dispatcher-servlet.xml中声明一个MultipartResolver:
xml 代码
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<bean id="multipartResolver"
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class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
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<!-- 设置上传文件的最大尺寸为1MB -->
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<property name="maxUploadSize">
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<value>1048576</value>
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</property>
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</bean>
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这样一旦某个Request是一个MultipartRequest,它就会首先被MultipartResolver处理,然后再转发相应的Controller。
在UploadImageController中,将HttpServletRequest转型为MultipartHttpServletRequest,就能非常方便地得到文件名和文件内容:
java 代码
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public ModelAndView handleRequest(HttpServletRequest request,
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HttpServletResponse response) throws Exception {
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// 转型为MultipartHttpRequest:
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MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
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// 获得文件:
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MultipartFile file = multipartRequest.getFile(" file ");
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// 获得文件名:
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String filename = file.getOriginalFilename();
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// 获得输入流:
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InputStream input = file.getInputStream();
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// 写入文件
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// 或者:
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File source = new File(localfileName.toString());
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multipartFile.transferTo(source);
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}
生成缩略图 (目录)
当用户上传了图片后,必须生成缩略图以便用户能快速浏览。我们不需借助第三方软件,JDK标准库就包含了图像处理的API。我们把一张图片按比例缩放到120X120大小,以下是关键代码:
java 代码
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public static void createPreviewImage(String srcFile, String destFile) {
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try {
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File fi = new File(srcFile); // src
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File fo = new File(destFile); // dest
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BufferedImage bis = ImageIO.read(fi);
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int w = bis.getWidth();
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int h = bis.getHeight();
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double scale = (double) w / h;
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int nw = IMAGE_SIZE; // final int IMAGE_SIZE = 120;
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int nh = (nw * h) / w;
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if (nh > IMAGE_SIZE) {
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nh = IMAGE_SIZE;
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nw = (nh * w) / h;
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}
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double sx = (double) nw / w;
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double sy = (double) nh / h;
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transform.setToScale(sx, sy);
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AffineTransformOp ato = new AffineTransformOp(transform, null);
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BufferedImage bid = new BufferedImage(nw, nh,
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BufferedImage.TYPE_3BYTE_BGR);
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ato.filter(bis, bid);
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ImageIO.write(bid, " jpeg ", fo);
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} catch (Exception e) {
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e.printStackTrace();
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throw new RuntimeException(
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" Failed in create preview image. Error: "
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+ e.getMessage());
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}
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}
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