Java实现登录验证码

登录验证码

servlet

/*

• 从请求中获取数据,获取验证码的session的值转为string类型,      
• 销毁,防止返回后验证码不刷新,重新验证成功      
• 判断验证码是否相同(忽略大小写)  
• 相同:创建user对象调用service层的方法验证返回结果是否为空      
   为空:创建session:储存错误信息,转发,登录页面显示登录名或密码错误    
   不为空:创建session:储存用户名,转发,到登录成功页面      
• 不相同:创建session:储存错误信息,登录页面显示验证码错误(判断如果session为null不显示) 

public class servlet extends httpservlet {  
protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {      
login login = new service.impl.login();   
string username =request.getparameter("username");  
string password = request.getparameter("password");   
string code = request.getparameter("code");        
object checkcode1 = request.getsession().getattribute("checkcode");
string checkcode = (string) checkcode1;        
request.getsession().removeattribute("checkcode");       
 if (checkcode!=null&&code.equalsignorecase(checkcode)){      
user u=new user();            
u.setusername(username);            
u.setpassword(password);    
user user = login.login(u);   
if (user!=null){                request.getsession().setattribute("username",username)         
request.getrequestdispatcher("success.jsp").forward(request,response);      
}else{                request.getsession().setattribute("userfail","用户名或密码错误");               
 request.getrequestdispatcher("index.jsp").forward(request,response);       
}        }else{            request.getsession().setattribute("codefail","验证码错误");    
request.getrequestdispatcher("index.jsp").forward(request,response);        
}                   
}

checkcodeservlet

public class checkcodeservlet extends httpservlet {    protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {       
//定义验证码框的长宽      
int width = 100;     
int height = 50;    
//创建image对象       
bufferedimage image = new bufferedimage(width, height, bufferedimage.type_int_rgb);    
//创建画笔对象    
graphics graphics = image.getgraphics();     
//设置画笔颜色      
graphics.setcolor(color.white);       
//填充背景      
graphics.fillrect(0, 0, width, height);        
//重新设定画笔颜色        graphics.setcolor(color.blue);     
//画验证码的边框      
graphics.drawrect(0, 0, width - 1, height - 1);    
//将验证码所要显示的内容组成字符串       
string s = "qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnm1234567890";   
//创建随机数对象        
random random = new random();      
//创建颜色数组       
color[] colors = {color.red, color.black, color.magenta, color.yellow, color.green};   
//创建builder对象用于组合验证码       
stringbuilder builder = new stringbuilder();    
//for循环画验证码    
for (int i = 1; i <= 4; i++) {         
//每个字母换一个颜色            graphics.setcolor(colors[new random().nextint(colors.length)]);     
//随机生成字符串下标          
int index = random.nextint(s.length());  
//通过字符串下标拿到字符        
char c = s.charat(index);       
//组合字符串          
builder.append(c);     
//设置验证码的字体       
graphics.setfont(new font("comic sans ms", font.bold, 20));       
//验证码所要摆放的位置     
graphics.drawstring(c + "", width / 5 * i, height / 2);       
}       
//将验证码转为string类型      
string s1 = builder.tostring();     
//存放在session中        request.getsession().setattribute("checkcode", s1);        //for循环画干扰线  
for (int i = 0; i < 30; i++) {         
//设置干扰线颜色         
graphics.setcolor(colors[new random().nextint(colors.length)]);   
//设置干扰线坐标           
int x = random.nextint(width);    
int y = random.nextint(height);     
int x1 = random.nextint(30);       
int y1 = random.nextint(30);     
int sin = random.nextboolean() ? 1 : -1;      
int cos = random.nextboolean() ? 1 : -1;            graphics.drawline(x, y, x + x1 * sin, y + y1 * cos);        }      
//输出验证码框    
imageio.write(image, "jpg", response.getoutputstream());  
}