巴巴运动网商品交易系统对图片的存放、下载以及压缩管理

本文参考传智播客巴巴运动网视频教程

 

构建保存图片的路径：

 

String pathdir = "/images/product/"+ productTypeId+ "/"+ productId+ "/prototype";//构建文件保存的目录

 

为什么要有那么多个目录，因为java本身不会去获取图片，而是调用了操作系统的一些接口来获取图片，如果一个目录下图片太多的话，操作系统获取图片的速度会变慢 ，所以巴巴运动网在构建图片路径的时候搞了多个目录，分散保存图片。

 

有了这个pathdir就可以得到图片保存目录的真实路径：

 

String realpathdir = request.getSession().getServletContext().getRealPath(pathdir);

 

获取了图片的真实路径后，就可以开始保存图片了：

 

File savedir = new File(realpathdir);
File file = saveFile(savedir, filename, imagefile.getFileData());	

imagefile为struts的FormFile类的对象， filename为文件名，这两个属性都可以从前台获取过来。以下是saveFile方法的代码：

/**
	 * 保存文件
	 * @param savedir 存放目录
	 * @param fileName 文件名称
	 * @param data 保存的内容
	 * @return 保存的文件
	 * @throws Exception
	 */
	public static File saveFile(File savedir, String fileName, byte[] data) throws Exception{
		if(!savedir.exists()) savedir.mkdirs();//如果目录不存在就创建
		File file = new File(savedir, fileName);
		FileOutputStream fileoutstream = new FileOutputStream(file);
		fileoutstream.write(data);
		fileoutstream.close();
		return file;
	}

 

保存完图片后还要保存一张图片的缩略图，宽度为140px

String pathdir140 = "/images/product/"+ productTypeId+ "/"+ productId+ "/140x";//140宽度的图片保存目录
String realpathdir140 = request.getSession().getServletContext().getRealPath(pathdir140);
File savedir140 = new File(realpathdir140);
if(!savedir140.exists()) savedir140.mkdirs();//如果目录不存在就创建
File file140 = new File(realpathdir140, filename);
ImageSizer.resize(file, file140, 140, ext);

 这里我们用到了一个从网上下的用于压缩图片的ImageSizer工具类的静态方法，resize方法传进去的四个参数分别代表原始图片对象，需要被压缩的图片对象，压缩宽度的大小，图片后缀名。这个工具类只能压缩jpg, png, gif(非动画)三种格式，如果想压缩更多的格式需要付费。以下是该工具类：

/**
 * 图像压缩工具
 * @author [e-mail]
 *
 */
public class ImageSizer {
    public static final MediaTracker tracker = new MediaTracker(new Component() {
        private static final long serialVersionUID = 1234162663955668507L;} 
    );
    /**
     * @param originalFile 原图像
     * @param resizedFile 压缩后的图像
     * @param width 图像宽
     * @param format 图片格式 jpg, png, gif(非动画)
     * @throws IOException
     */
    public static void resize(File originalFile, File resizedFile, int width, String format) throws IOException {
        if(format!=null && "gif".equals(format.toLowerCase())){
        	resize(originalFile, resizedFile, width, 1);
        	return;
        }
        FileInputStream fis = new FileInputStream(originalFile);
        ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        int readLength = -1;
        int bufferSize = 1024;
        byte bytes[] = new byte[bufferSize];
        while ((readLength = fis.read(bytes, 0, bufferSize)) != -1) {
            byteStream.write(bytes, 0, readLength);
        }
        byte[] in = byteStream.toByteArray();
        fis.close();
        byteStream.close();
        
    	Image inputImage = Toolkit.getDefaultToolkit().createImage( in );
        waitForImage( inputImage );
        int imageWidth = inputImage.getWidth( null );
        if ( imageWidth < 1 ) 
           throw new IllegalArgumentException( "image width " + imageWidth + " is out of range" );
        int imageHeight = inputImage.getHeight( null );
        if ( imageHeight < 1 ) 
           throw new IllegalArgumentException( "image height " + imageHeight + " is out of range" );
        
        // Create output image.
        int height = -1;
        double scaleW = (double) imageWidth / (double) width;
        double scaleY = (double) imageHeight / (double) height;
        if (scaleW >= 0 && scaleY >=0) {
            if (scaleW > scaleY) {
                height = -1;
            } else {
                width = -1;
            }
        }
        Image outputImage = inputImage.getScaledInstance( width, height, java.awt.Image.SCALE_DEFAULT);
        checkImage( outputImage );        
        encode(new FileOutputStream(resizedFile), outputImage, format);        
    }    

    /** Checks the given image for valid width and height. */
    private static void checkImage( Image image ) {
       waitForImage( image );
       int imageWidth = image.getWidth( null );
       if ( imageWidth < 1 ) 
          throw new IllegalArgumentException( "image width " + imageWidth + " is out of range" );
       int imageHeight = image.getHeight( null );
       if ( imageHeight < 1 ) 
          throw new IllegalArgumentException( "image height " + imageHeight + " is out of range" );
    }

    /** Waits for given image to load. Use before querying image height/width/colors. */
    private static void waitForImage( Image image ) {
       try {
          tracker.addImage( image, 0 );
          tracker.waitForID( 0 );
          tracker.removeImage(image, 0);
       } catch( InterruptedException e ) { e.printStackTrace(); }
    } 

    /** Encodes the given image at the given quality to the output stream. */
    private static void encode( OutputStream outputStream, Image outputImage, String format ) 
       throws java.io.IOException {
       int outputWidth  = outputImage.getWidth( null );
       if ( outputWidth < 1 ) 
          throw new IllegalArgumentException( "output image width " + outputWidth + " is out of range" );
       int outputHeight = outputImage.getHeight( null );
       if ( outputHeight < 1 ) 
          throw new IllegalArgumentException( "output image height " + outputHeight + " is out of range" );

       // Get a buffered image from the image.
       BufferedImage bi = new BufferedImage( outputWidth, outputHeight,
          BufferedImage.TYPE_INT_RGB );                                                   
       Graphics2D biContext = bi.createGraphics();
       biContext.drawImage( outputImage, 0, 0, null );
       ImageIO.write(bi, format, outputStream);
       outputStream.flush();      
    } 
    
	/**
	 * 缩放gif图片
	 * @param originalFile 原图片
	 * @param resizedFile 缩放后的图片
	 * @param newWidth 宽度
	 * @param quality 缩放比例 (等比例)
	 * @throws IOException
	 */
    private static void resize(File originalFile, File resizedFile, int newWidth, float quality) throws IOException {
        if (quality < 0 || quality > 1) {
            throw new IllegalArgumentException("Quality has to be between 0 and 1");
        } 
        ImageIcon ii = new ImageIcon(originalFile.getCanonicalPath());
        Image i = ii.getImage();
        Image resizedImage = null; 
        int iWidth = i.getWidth(null);
        int iHeight = i.getHeight(null); 
        if (iWidth > iHeight) {
            resizedImage = i.getScaledInstance(newWidth, (newWidth * iHeight) / iWidth, Image.SCALE_SMOOTH);
        } else {
            resizedImage = i.getScaledInstance((newWidth * iWidth) / iHeight, newWidth, Image.SCALE_SMOOTH);
        } 
        // This code ensures that all the pixels in the image are loaded.
        Image temp = new ImageIcon(resizedImage).getImage(); 
        // Create the buffered image.
        BufferedImage bufferedImage = new BufferedImage(temp.getWidth(null), temp.getHeight(null),
                                                        BufferedImage.TYPE_INT_RGB); 
        // Copy image to buffered image.
        Graphics g = bufferedImage.createGraphics(); 
        // Clear background and paint the image.
        g.setColor(Color.white);
        g.fillRect(0, 0, temp.getWidth(null), temp.getHeight(null));
        g.drawImage(temp, 0, 0, null);
        g.dispose(); 
        // Soften.
        float softenFactor = 0.05f;
        float[] softenArray = {0, softenFactor, 0, softenFactor, 1-(softenFactor*4), softenFactor, 0, softenFactor, 0};
        Kernel kernel = new Kernel(3, 3, softenArray);
        ConvolveOp cOp = new ConvolveOp(kernel, ConvolveOp.EDGE_NO_OP, null);
        bufferedImage = cOp.filter(bufferedImage, null); 
        // Write the jpeg to a file.
        FileOutputStream out = new FileOutputStream(resizedFile);        
        // Encodes image as a JPEG data stream
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); 
        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bufferedImage); 
        param.setQuality(quality, true); 
        encoder.setJPEGEncodeParam(param);
        encoder.encode(bufferedImage);
    }
}

 

允许用户上传文件，那么我们一定要注意安全，如果用户上传了一个jsp文件，而这个文件的上传路径敲好能被用户访问到，那么用户可能会在这个jsp文件里面做一个对网站其他文件的文件操作，可以将文件保存到web-inf下面，如果用户需要下载，我们就写一个servlet读取这个文件，以流的方式返回给用户。