利用獨立的servlet在頁面顯示圖片

web頁面上的圖片顯示可以指定了一個url, 直接訪問後臺的一個servlet. 在後臺數據庫可以專門建一個圖片庫. 以下是一個簡單的示例.在這裏採用了imageJ-v1.37項目(網址: http://rsb.info.nih.gov/ij/ ) 進行圖片處理.

 

1, ImageViewServlet 

package com.hank.web.servlet; import java.io.IOException; import java.io.OutputStream; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.context.ApplicationContext; import org.springframework.web.context.support.WebApplicationContextUtils; import com.hank.model.ConAttachs; import com.hank.service.ConAttachsManager; import com.hank.util.ImageUtil; /** * @author hank * @date 2007-9-12 03:49:57 * @version */ public class ImageViewServlet extends HttpServlet { private static final long serialVersionUID = 714920135153152003L; protected final transient Log log = LogFactory.getLog(getClass()); @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { execute(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { execute(request, response); } public void execute(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { String[] infos = request.getPathInfo().split("/"); String name=infos[1]; String id=infos[2].substring(0, infos[2].lastIndexOf('.')); OutputStream out = response.getOutputStream(); ApplicationContext ctx = WebApplicationContextUtils.getWebApplicationContext(getServletContext()); if (name.equals("conAttach")){ ConAttachsManager mgr = (ConAttachsManager)ctx.getBean("conAttachsManager"); ConAttachs conAttachs = mgr.getConAttachsByContextId(id); if(conAttachs.getFType().intValue()==1){ return; } byte[] images = conAttachs.getContextFile(); try { response.setContentType(conAttachs.getFhttpContent());//設置contentType ImageUtil.outLogo(images,out,200,100);//顯示200*100的縮略圖 response.getOutputStream().flush(); } catch (Exception e) { e.printStackTrace(); }finally{ if(out!=null){ out.close(); } } }else if(){ ... ... } } }

 

2, ImageUtil

package com.hank.util; import ij.ImagePlus; import ij.io.Opener; import ij.process.Blitter; import ij.process.ImageProcessor; import java.awt.Graphics; import java.awt.Image; import java.awt.image.BufferedImage; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import java.io.PrintWriter; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.sun.image.codec.jpeg.ImageFormatException; import com.sun.image.codec.jpeg.JPEGCodec; import com.sun.image.codec.jpeg.JPEGImageEncoder; /** * @author hank * @date 2007-9-12 03:14:21 * @version */ public class ImageUtil { protected final transient Log log = LogFactory.getLog(getClass()); public static void outLogo(byte[] source,OutputStream out,int dwidth,int dheight) throws Exception{ BufferedInputStream stream = new BufferedInputStream((new ByteArrayInputStream(source)),8092);//控制流速 Image src = javax.imageio.ImageIO.read(stream); int width=src.getWidth(null); int height=src.getHeight(null); int towidth,toheight; if (width>dwidth || height>dheight){ if (((float)width/dwidth)>=((float)height/dheight)){ towidth = dwidth; toheight = (height*dwidth)/width; }else{ toheight = dheight; towidth = (width* dheight)/height; } }else{ towidth= width; toheight=height; } BufferedImage tag = new BufferedImage(towidth,toheight,BufferedImage.TYPE_INT_RGB); tag.getGraphics().drawImage(src,0,0,towidth,toheight,null); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); encoder.encode(tag); } }

 

3, 在web.xml中配置 servlet

 

4, 頁面上直接使用img標籤指定src即可