利用独立的servlet在页面显示图片

        web页面上的图片显示可以指定了一个url, 直接访问后台的一个servlet. 在后台数据库可以专门建一个图片库. 以下是一个简单的示例.在这里采用了imageJ-v1.37项目(网址: http://rsb.info.nih.gov/ij/ ) 进行图片处理.

 

1, ImageViewServlet 

java 代码

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());//设置contentType
                ImageUtil.outLogo(images,out,200,100);//显示200*100的缩略图
                response.getOutputStream().flush();
            } catch (Exception e) {
                e.printStackTrace();
            }finally{
                if(out!=null){
                    out.close();
                }
            }
        }else if(){
            ... ...
        }
    }
}

 2, ImageUtil

java 代码

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 , 页面上直接使用img标签指定src即可