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java/jsp学习系列之十四(jsp生成jpeg图片用于投票)——-本文章为东方一蛇转载。转自东方一蛇的网站www.wodejia.net
一、前言
本文原作者为tony wang ，该文章涉及到文件的读写和jpg图片的自动生成。利用jsp+servlet的技术，jsp调用servlet生成图片。
二、首文件index.jsp如下：
冰帆调查
三、写文件write.jsp
四、servlet原代码：voteimage.java :
/* author: tony wang e-mail: lucky_tony@163.net date: 2001-01-01 如果对程序有什么疑问，可以和我联系，另外程序如果有什么bug，麻烦指出！！ */ import java.io.*; import java.util.*; import com.sun.image.codec.jpeg.*; import javax.servlet.*; import javax.servlet.http.*; import java.awt.*; import java.awt.geom.*; import java.awt.image.*; public class voteimage extends httpservlet { private string strfile = null; private color color[]={color.red,color.black,color.orange,color.green}; private int baseang = 30; public void doget(httpservletrequest request,httpservletresponse response) throws servletexception,ioexception { strfile = request.getrealpath(“count.txt“); float[][] xy = new float[4][2]; xy = getnumandpercent(strfile);
int[] ang = new int[4]; ang[0] = (int)(xy[0][1]*360); ang[1] = (int)(xy[1][1]*360); ang[2] = (int)(xy[2][1]*360); ang[3] = 360-ang[0]-ang[1]-ang[2];
response.setheader(“cache-control“,“no-store“); response.setdateheader(“expires“,0); response.setcontenttype(“image/jpeg“); servletoutputstream out=response.getoutputstream(); bufferedimage image=new bufferedimage(150,100,bufferedimage.type_int_rgb); graphics2d g=(graphics2d)image.getgraphics(); g.setrenderinghint(renderinghints.key_antialiasing,renderinghints.value_antialias_on); g.setcolor(color.white); g.fillrect(0,0,150,100); affinetransform at = null; arc2d arc = null; int fromang = baseang;
at = affinetransform.getrotateinstance((-20*java.lang.math.pi)/180,45,37); g.settransform(at);
int r =6; int dx = (int)(r*java.lang.math.cos((baseang+ang[0])/2.0*java.lang.math.pi/180)); int dy = (int)(r*java.lang.math.sin((baseang+ang[0])/2.0*java.lang.math.pi/180)); arc = new arc2d.double(10+dx,24-dy,80,50,fromang,ang[0],arc2d.pie); g.setcolor(color[0]); g.fill(arc); fromang+=ang[0]; for (int i=1;i<4;i++) { g.setcolor(color[i]); arc = new arc2d.double(10,24,80,50,fromang,ang[i],arc2d.pie); g.fill(arc); fromang+=ang[i]; if (fromang>360) { fromang-=360; } }
at = affinetransform.getrotateinstance(0,arc.getcenterx(),arc.getcentery()); g.settransform(at);
for (int i=0;i<4;i++){ g.setcolor(color[i]); g.fillrect(100,15*i+20,10,10); g.drawstring((char)(‘a‘+i)+““,120,15*i+20+8); } jpegimageencoder encoder=jpegcodec.createjpegencoder(out); encoder.encode(image); out.close(); }
public void dopost(httpservletrequest request,httpservletresponse response) throws servletexception,ioexception { doget(request,response); }
public synchronized float[][] getnumandpercent(string sfilename) { float xx[][] = new float[4][2]; int totalnum = 0 ; string strtemp = null; int i = 0; java.io.randomaccessfile rf = null; try { rf = new java.io.randomaccessfile (sfilename,“r“); } catch(exception e) { system.out.println(e); system.exit(0); } for (i=0;i<4;i++) { int m=0; try { strtemp = rf.readline(); } catch (exception e){ strtemp = “0“; }
if (strtemp == null) strtemp = “0“; m = new integer(strtemp).intvalue(); xx[i][0]=m; totalnum += m; } if (totalnum==0) totalnum=1; for ( i=0;i<4;i++){ xx[i][1] = xx[i][0]/totalnum; } return xx; } }
五、在index.jsp目录下建立question.txt和count.txt文件分别用来保存投票的问题和投票的数量，用户投票后，就修改count.txt的值。
为了对原作者表示感谢，这2个文件内容不变化，如下：
question.txt:
yes,i think so!
no,i dont think so!
sorry,i dont know the answer!
count.txt:
12
9
5
9
六、目录结构：
(1)jsp文件和txt文件同一个目录
(2).java文件是servlet目录下
七、测试：
http://[server:port]/dir/index.jsp
