在网站制作中通常需要上传附件，而对于附件我们往往希望在其名称前面有类似于Windows系统中的类型图标，那么怎么根据附件的类型来显示不同的图标呢？目前有两种解决方案：
第一种：将所有类型文件的图标图片放置到项目中，然后通过分析文件的扩展名来调用相应的图片，这种方式比较简单常见，但是我们往往无法弄到所有文件类型的图标，而且也不能排除意外情况的出现，这里就不在介绍了；
第二种：通过java调用系统的文件类型图标然后显示出来，好处是可以显示跟操作系统中一模一样的图标，但是要复杂一些，下面详细介绍。
1、JSP
Java代码
<img src="fileAction!dispalyIcon?dirName=<%=request.getAttribute("fileName").toString()%>" style="width:16px;height:16px;"/>
2、fileAction
Java代码
@Component("fileAction")
public class FileAction extends ActionSupport {
private String dirName;
public String getDirName() {
return dirName;
}
public void setDirName(String dirName) {
this.dirName = dirName;
}
public void dispalyIcon() {
HttpServletResponse response = ServletActionContext.getResponse();
response.setContentType("image/png");
try {
OutputStream sos = response.getOutputStream();
BufferedImage myImage = CommonTool.getImageByFileTyle(dirName);
ImageIO.write(myImage, "png", sos);
sos.flush();
sos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
3、CommonTool
Java代码
public class CommonTool {
public static BufferedImage getImageByFileTyle(String filename)
throws FileNotFoundException {
File file = null;
String extension = filename.substring(filename.lastIndexOf("."))
.toLowerCase();
try {
file = File.createTempFile("icon", extension);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return toBufferedImage(toImage(toIcon(file)));
}
public static Icon toIcon(File file) throws FileNotFoundException {
ShellFolder shellFolder = ShellFolder.getShellFolder(file);
Icon icon = new ImageIcon(shellFolder.getIcon(true));
return icon;
}
public static Image toImage(Icon icon) {
if (icon instanceof ImageIcon) {
return ((ImageIcon) icon).getImage();
} else {
int w = icon.getIconWidth();
int h = icon.getIconHeight();
GraphicsEnvironment ge = GraphicsEnvironment
.getLocalGraphicsEnvironment();
GraphicsDevice gd = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gd.getDefaultConfiguration();
BufferedImage image = gc.createCompatibleImage(w, h);
Graphics2D g = image.createGraphics();
icon.paintIcon(null, g, 0, 0);
g.dispose();
return image;
}
}
private static boolean hasAlpha(Image image) {
// If buffered image, the color model is readily available
if (image instanceof BufferedImage) {
BufferedImage bimage = (BufferedImage) image;
return bimage.getColorModel().hasAlpha();
}
// Use a pixel grabber to retrieve the image's color model;
// grabbing a single pixel is usually sufficient
PixelGrabber pg = new PixelGrabber(image, 0, 0, 1, 1, false);
try {
pg.grabPixels();
} catch (InterruptedException e) {
}
// Get the image's color model
ColorModel cm = pg.getColorModel();
return cm.hasAlpha();
}
// This method returns a buffered image with the contents of an image
public static BufferedImage toBufferedImage(Image image) {
if (image instanceof BufferedImage) {
return (BufferedImage) image;
}
// This code ensures that all the pixels in the image are loaded
image = new ImageIcon(image).getImage();
// Determine if the image has transparent pixels; for this method's
// implementation, see Determining If an Image Has Transparent Pixels
boolean hasAlpha = hasAlpha(image);
// Create a buffered image with a format that's compatible with the
// screen
BufferedImage bimage = null;
GraphicsEnvironment ge = GraphicsEnvironment
.getLocalGraphicsEnvironment();
try {
// Determine the type of transparency of the new buffered image
int transparency = Transparency.OPAQUE;
if (hasAlpha) {
transparency = Transparency.BITMASK;
}
// Create the buffered image
GraphicsDevice gs = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gs.getDefaultConfiguration();
bimage = gc.createCompatibleImage(image.getWidth(null), image
.getHeight(null), transparency);
} catch (HeadlessException e) {
// The system does not have a screen
}
if (bimage == null) {
// Create a buffered image using the default color model
int type = BufferedImage.TYPE_INT_RGB;
if (hasAlpha) {
type = BufferedImage.TYPE_INT_ARGB;
}
bimage = new BufferedImage(image.getWidth(null), image
.getHeight(null), type);
}
// Copy image to buffered image
Graphics g = bimage.createGraphics();
// Paint the image onto the buffered image
g.drawImage(image, 0, 0, null);
g.dispose();
return bimage;
}
}
4、struts.xml
Java代码
<action name="fileAction" class="com.render.action.cyl.FileAction">
<result name="input">login.jsp</result>
</action>
