Servlets javaservlet会话维护
我已经开发了用于生成验证码和添加会话名称的servletServlets javaservlet会话维护,servlets,httpsession,Servlets,Httpsession,我已经开发了用于生成验证码和添加会话名称的servlet import javax.servlet.*; import java.io.*; import java.awt.*; import java.util.Random; import java.awt.image.*; import javax.imageio.*; import javax.servlet.http.*; public class capta extends HttpServlet { final int L
import javax.servlet.*;
import java.io.*;
import java.awt.*;
import java.util.Random;
import java.awt.image.*;
import javax.imageio.*;
import javax.servlet.http.*;
public class capta extends HttpServlet
{
final int LEN=10;
BufferedImage image;
Random rnd;
public void doGet(HttpServletRequest req,HttpServletResponse rep)
{
try
{
image = new BufferedImage(200, 80, BufferedImage.TYPE_INT_RGB);
rnd=new Random();
rep.setContentType("image/jpeg");
String random_String=getRandomNumbers();
HttpSession ses=req.getSession();
ses.setAttribute("code",random_String);
Graphics g = image.getGraphics();
g.setFont(new Font("Maiandra GD",1,30));
g.setColor(Color.blue);
g.drawString(random_String,3,50);
g.dispose();
/// it was here
ImageIO.write(image, "jpg", rep.getOutputStream());
}
catch(Exception e)
{
}
}
private String getRandomNumbers()
{
StringBuffer str=new StringBuffer();
for(int i=1;i<=9;i++)
{
str.append(new Integer(rnd.nextInt(9)).toString());
}
return str.toString();
}
public void doPost(HttpServletRequest req,HttpServletResponse rep)throws ServletException , IOException
{
doGet(req,rep);
}
}
生成Capta代码
import javax.servlet.*;
import java.io.*;
import java.awt.*;
import java.util.Random;
import java.awt.image.*;
import javax.imageio.*;
import javax.servlet.http.*;
public class capta extends HttpServlet
{
final int LEN=10;
BufferedImage image;
Random rnd;
public void doGet(HttpServletRequest req,HttpServletResponse rep)
{
try
{
image = new BufferedImage(200, 80, BufferedImage.TYPE_INT_RGB);
rnd=new Random();
rep.setContentType("image/jpeg");
String random_String=getRandomNumbers();
HttpSession ses=req.getSession();
ses.setAttribute("code",random_String);
Graphics g = image.getGraphics();
g.setFont(new Font("Maiandra GD",1,30));
g.setColor(Color.blue);
g.drawString(random_String,3,50);
g.dispose();
/// it was here
ImageIO.write(image, "jpg", rep.getOutputStream());
}
catch(Exception e)
{
}
}
private String getRandomNumbers()
{
StringBuffer str=new StringBuffer();
for(int i=1;i<=9;i++)
{
str.append(new Integer(rnd.nextInt(9)).toString());
}
return str.toString();
}
public void doPost(HttpServletRequest req,HttpServletResponse rep)throws ServletException , IOException
{
doGet(req,rep);
}
}
import javax.servlet.*;
导入java.io.*;
导入java.awt.*;
导入java.util.Random;
导入java.awt.image.*;
导入javax.imageio.*;
导入javax.servlet.http.*;
公共类capta扩展HttpServlet
{
最终整数长度=10;
缓冲图像;
随机rnd;
公共无效数据集(HttpServletRequest-req、HttpServletResponse-rep)
{
尝试
{
图像=新的BuffereImage(200,80,BuffereImage.TYPE_INT_RGB);
rnd=新随机数();
rep.setContentType(“图像/jpeg”);
String random_String=getRandomNumbers();
HttpSession ses=req.getSession();
ses.setAttribute(“代码”,随机字符串);
Graphics g=image.getGraphics();
g、 setFont(新字体(“Maiandra GD”,1,30));
g、 setColor(Color.blue);
g、 抽绳(随机抽绳,3,50);
g、 处置();
///就在这里
write(image,“jpg”,rep.getOutputStream());
}
捕获(例外e)
{
}
}
私有字符串getRandomNumbers()
{
StringBuffer str=新的StringBuffer();
对于(int i=1;i您的程序流是错误的,会话值为null,因为在调用capta servlet之前就调用了capta\u测试servlet
看看这个简单的教程。希望它能帮助你走上正确的道路
将随机数生成逻辑放入capta_testservlet中,并将该数字放入会话。由于您正在呈现HTML,因此页面加载后会像这样调用captaservlet,并且不会使会话无效
随机数生成器
import javax.servlet.*;
import java.io.*;
import javax.servlet.http.*;
public class capta_test extends HttpServlet
{
public void doGet(HttpServletRequest req,HttpServletResponse rep)
{
PrintWriter out=null;
try
{
String original=getRandomNumbers();
HttpSession ses=req.getSession(false);
ses.setAttribute("code",random_String);
String input=req.getParameter("txt_capta");
out=rep.getWriter();
rep.setContentType("text/html");
out.println("<html><head><title>Capta Test</title></head>");
out.println("<body>");
out.println("<h1> Capta is Generated </h1>");
out.println("<img src=\"http://localhost:8080/mahesh/capta\" />");
out.println("<h1>Original Value "+original+"</h1>");
out.println("</body>");
out.println("</html>");
}
catch(Exception e)
{
}
}
public void doPost(HttpServletRequest req,HttpServletResponse rep)throws ServletException , IOException
{
doGet(req,rep);
}
private String getRandomNumbers()
{
Random rnd=new Random();
StringBuffer str=new StringBuffer();
for(int i=1;i<=9;i++)
{
str.append(new Integer(rnd.nextInt(9)).toString());
}
return str.toString();
}
}
为什么您认为/期望验证码图像servlet在验证码测试HTML servlet之前运行?浏览器在获取验证码图像servlet的URL之前,如何在验证码测试HTML servlet生成的HTML输出中的
元素中点击验证码图像servlet?请尝试逻辑思考。顺便说一句,这是一个相当糟糕的问题r captcha algo。除了数字,整个captcha都是静态的。编写一个小型OCR程序来查找数字并集成到一个机器人中非常容易。@BalusC我知道了,但我如何首先运行servlet,即生成图像。@BalusC:我开发servlet是为了学习。。
import javax.servlet.*;
import java.io.*;
import java.awt.*;
import java.util.Random;
import java.awt.image.*;
import javax.imageio.*;
import javax.servlet.http.*;
public class capta extends HttpServlet
{
final int LEN=10;
BufferedImage image;
public void doGet(HttpServletRequest req,HttpServletResponse rep)
{
try
{
HttpSession ses=req.getSession(false);
String random_String=(String)ses.getAttribute("code");
image = new BufferedImage(200, 80, BufferedImage.TYPE_INT_RGB);
rep.setContentType("image/jpeg");
Graphics g = image.getGraphics();
g.setFont(new Font("Maiandra GD",1,30));
g.setColor(Color.blue);
g.drawString(random_String,3,50);
g.dispose();
/// it was here
ImageIO.write(image, "jpg", rep.getOutputStream());
}
catch(Exception e)
{
}
}
public void doPost(HttpServletRequest req,HttpServletResponse rep)throws ServletException , IOException
{
doGet(req,rep);
}
}