1、Servlet   代码

public class ZoomImgServlet extends HttpServlet implements Servlet {

public void init(ServletConfig conf)throws ServletException {}
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        int width=352,height=233;//这是设置图片显示的宽和高
        String srcImgPath=“http://pic.to8to.com/attch/day_160218/20160218_d968438a2434b62ba59dH7q5KEzTS6OH.png”;
        resp.setDateHeader("Expires", 0L);
        resp.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
        resp.addHeader("Cache-Control", "post-check=0, pre-check=0");
        resp.setHeader("Pragma", "no-cache");// 设置响应头信息，不缓存此内容
        resp.setContentType("image/jpeg");
        URL url = new URL(srcImgPath);  
        //打开链接  
        HttpURLConnection conn = (HttpURLConnection)url.openConnection();  
        //设置请求方式为"GET"  
        conn.setRequestMethod("GET");  
        //超时响应时间为5秒  
        conn.setConnectTimeout(5 * 1000);  
        InputStream inStream = conn.getInputStream();
        byte[] data = null;
        ServletOutputStream out=null;
        try {
            data = readInputStream(inStream);
            ByteArrayInputStream bin = new ByteArrayInputStream(data);  
            Image srcImg = ImageIO.read(bin);  
            BufferedImage buffImg = null;  
            buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);  
            buffImg.getGraphics().drawImage(srcImg.getScaledInstance(width, height, Image.SCALE_SMOOTH), 0,0, null);  
            out = resp.getOutputStream();
            ImageIO.write(buffImg, "PNG", out);
            out.flush();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            out.close();
        }
    }
    
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        super.doGet(req, resp);
    }
    
    
     private static byte[] readInputStream(InputStream inStream) throws Exception{  
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();  
        //创建一个Buffer字符串  
        byte[] buffer = new byte[1024];  
        //每次读取的字符串长度，如果为-1，代表全部读取完毕  
        int len = 0;  
        //使用一个输入流从buffer里把数据读取出来  
        while( (len=inStream.read(buffer)) != -1 ){  
            //用输出流往buffer里写入数据，中间参数代表从哪个位置开始读，len代表读取的长度  
            outStream.write(buffer, 0, len);
        }
        //关闭输入流  
        inStream.close();  
        //把outStream里的数据写入内存  
        return outStream.toByteArray();  
    }  
}

2、web.xml 配置

<servlet>
    <servlet-name>zoomImgServlet</servlet-name>
    <servlet-class>com.test.servlet.ZoomImgServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>zoomImgServlet</servlet-name>
    <url-pattern>/zoomImg.jpg</url-pattern>
  </servlet-mapping>

3、页面调用

<img src="${path}/zoomImg.jpg" />