JAVA/JSP學習系列之十二(JSP產生jpeg圖片用於投票)

最後更新：2018-12-03 來源：互聯網

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一、前言

　　本文原作者為Tony Wang ，該文章涉及到檔案的讀寫和jpg圖片的自動產生。利用jsp+servlet的技術，jsp調用servlet產生圖片。

二、首檔案index.jsp如下：

<%--

Author: Tony Wang

E-mail: lucky_tony@163.net

Date: 2001-01-01

如果對程式有什麼疑問，可以和我聯絡，另外程式如果有什麼bug，麻煩指出！！

--%>

<%@ page contentType="text/html;charSet=gb2312"%>
<%
response.setHeader("Cache-Control","no-store");
response.setDateHeader("Expires",0);
%>
<%!
public String[] getQuestion(String s)
{
String[] strQ = new String[4];
String strTemp = null;
int i;
java.io.RandomAccessFile rf = null;
try {
rf = new java.io.RandomAccessFile(s,"r");
} catch(Exception e)
{
System.out.println(e);
System.exit(0);
}
for(i=0;i<4;i++)
{
try {
strTemp = rf.readLine();
} catch(Exception e) {
strTemp = "None Question";
}
if(strTemp==null)strTemp = "None Question";
strQ[i] = strTemp;
}
return strQ;
}

<%
String s = null;
String[] question = new String[4];

s = request.getRealPath("question.txt");
question = getQuestion(s);
%>

<body>
<table width="180" border="1" bordercolor="#999999">
<tr>
<td align=center>冰帆調查</td>
</tr>
<form name=frm method=post action=write.jsp>
<tr>
<td>
<%
String ss = null;
for (int i=0;i<4;i++)
{
ss = "<input type=/"radio/" name=/"choice/" value=" + i+">"+

(char)('A'+i)+"、"+ question[i]+"<br>";
out.println(ss);
}
%>
</td>
</tr>
<tr>
<td align=center><input type=submit value="我投一票"></td>
</tr>
<tr>
<td align=center><img src="/vote/servlet/VoteImage" width=150

height=100></td>
</tr>
</form>
</table>
</body>
</html>

三、寫檔案write.jsp

<%--
Author: Tony Wang
E-mail: lucky_tony@163.net
Date: 2001-01-01
如果對程式有什麼疑問，可以和我聯絡，
另外程式如果有什麼bug，麻煩指出！！
--%>
<%!
public int[] getNumber(String s)
{
int[] mCount = new int[4];
String strTemp = null;
int i;
java.io.RandomAccessFile rf = null;
try {
rf = new java.io.RandomAccessFile(s,"r");
} catch(Exception e)
{
System.out.println(e);
System.exit(0);
}
for(i=0;i<4;i++)
{
try {
strTemp = rf.readLine();
} catch(Exception e) {
strTemp = "0";
}
if(strTemp==null)strTemp = "0";
mCount[i] = new Integer(strTemp).intValue();
}
return mCount;
}

public void setNumber(String s,int[] x)
{
try {
java.io.PrintWriter pw = new java.io.PrintWriter(new java.io.

FileOutputStream(s));
for (int i=0;i<4;i++){
pw.println(x[i]+"");
}
pw.close();
} catch(Exception e) {
System.out.println("Write file error:"+e.getMessage());
}
}
%>

<%
String tmp = null;
int choice = -1;
int[] count = new int[4];
tmp = request.getParameter("choice");
if (tmp==null){
} else {
choice = new Integer(tmp).intValue();
}
/////////////
String s = request.getRealPath("count.txt");
if(choice>=0){
count = getNumber(s);
count[choice]++;
setNumber(s,count);
}

response.sendRedirect("index.jsp");
%>
四、servlet原代碼：VoteImage.java :

/*
Author: Tony Wang
E-mail: lucky_tony@163.net
Date: 2001-01-01
如果對程式有什麼疑問，可以和我聯絡，
另外程式如果有什麼bug，麻煩指出！！
*/
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目錄下建立question.txt和count.txt檔案分別用來儲存投

票的問題和投票的數量，使用者投票後，就修改count.txt的值。

為了對原作者表示感謝，這2個檔案內容不變化，如下：

question.txt:

Yes,I think so!

No,I dont think so!

Sorry,I dont know the answer!

count.txt:

六、目錄結構：

(1)jsp檔案和txt檔案同一個目錄

(2).java檔案是servlet目錄下

七、測試：

http://[server:port]/dir/index.jsp

本文章原先以中文撰寫並發佈於 aliyun.com，亦設英文版本，僅作資訊用途。本網站不對文章的準確性，完整性或可靠性或其任何翻譯作出任何明示或暗示的陳述或保證。如對該文章有任何疑慮或投訴，請傳送電郵至 info-contact@alibabacloud.com 並提供相關疑慮或投訴的詳細說明。職員會於 5 個工作天內與您聯絡，一經驗證之後，即會刪除該侵權內容。

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