用servlet生成一个图片时报错

以下是servlet的代码：
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import java.io.*;
import java.awt.*;
import java.awt.image.*;
import java.net.URL;import javax.servlet.*;
import javax.servlet.http.*;
import javax.imageio.ImageIO;
import com.sun.image.codec.jpeg.*;public class CreateImageServlet extends HttpServlet {    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        response.setContentType("image/jpeg");
        /*
         * public ServletOutputStream getOutputStream() ：
         * 返回一个适合在响应中写入二进制数据的ServletOutputStream类
         * public abstract class ServletOutputStream（）：
         * 提供一个向客户端发送二进制数据的输出流
        */
        createImage(response.getOutputStream());
    }
    
    //生成图像的方法
    private void createImage(OutputStream out) throws IOException{        BufferedImage bi2 = ImageIO.read(new URL("D:\\Documents and Settings\\My Pictures\\piao.jpg"));        
        // encode:
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi2);
        param.setQuality(1.0f, false);
        encoder.setJPEGEncodeParam(param);
        try {
            encoder.encode(bi2);
        }
        catch(IOException ioe) {
            ioe.printStackTrace();
        }
    }
}
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以下是报错内容：
Servlet.service() for servlet CreateImageServlet threw exception
java.net.MalformedURLException: unknown protocol: d
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at image_edit.CreateImageServlet.createImage(CreateImageServlet.java:50)
at image_edit.CreateImageServlet.doGet(CreateImageServlet.java:25)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)