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JSP references a servlet-generated verification code demo _JSP programming

Source: Internet
Author: User
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This demo code consists mainly of the following three parts:
1.checkcode.java: Used to generate verification code
2.checkCodeServler
3.check.jsp Verification

Here's what the Checkcode.java:

Copy Code code as follows:

Used to get four-bit random numbers
Private char maptable[] = {' 0 ', ' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ', ' 6 ', ' 7 ', ' 8 ', ' 9 '};

Generates a CAPTCHA and returns a randomly generated number
Public String getensure (int width, int height, outputstream os) {
if (width <= 0)
width = 60;
if (height <= 0)
height = 20;

BufferedImage image = new BufferedImage (width, height,bufferedimage.type_int_rgb);

Get Graphics context
Graphics g = image.getgraphics ();

Set Background color
G.setcolor (New Color (0xDCCCCC));
G.fillrect (0, 0, width, height);

Draw a border
G.setcolor (Color.Black);
G.drawrect (0, 0, width-1, height-1);

Take a randomly generated authentication code
String strensure = "";

4 represents 4-bit captcha
for (int i = 0; i < 4; ++i) {
Strensure + = maptable[(int) (Maptable.length * Math.random ())];
}

Display the authentication code in the image
G.setcolor (color.red);
G.setfont (New Font ("Atlantic Inline", Font.plain, 14));

The exact coordinates of the painting
String str = strensure.substring (0, 1);
g.DrawString (str, 8, 14);
str = strensure.substring (1, 2);
g.DrawString (str, 20, 15);
str = strensure.substring (2, 3);
g.DrawString (str, 35, 18);
str = strensure.substring (3, 4);
g.DrawString (str, 45, 15);

Releasing the graphics context
G.dispose ();

try{
Output image to Page
Imageio.write (Image, "JPEG", OS);
catch (IOException e) {
Return "";
}

return strensure; Returns the generated random number
}

And again, the Checkcodeservlet content.

Copy Code code as follows:

public void doget (HttpServletRequest request, httpservletresponse response)
Throws Servletexception, IOException {
DoPost (request, response);
}

public void DoPost (HttpServletRequest request, httpservletresponse response)
Throws Servletexception, IOException {
Disable caching, each time you access this page, regenerate
Response.setheader ("Pragma", "No-cache");
Response.setheader ("Cache-control", "No-cache");
Response.setdateheader ("Expires", 0);

To generate an instance object for a validation code
Checkcode ie = new Checkcode ();

The method inside the call returns the string in the generated verification code
String str = ie.getensure (0,0,response.getoutputstream ());

Gets the session and saves the string in session, making the basis for the back contrast
HttpSession session = Request.getsession ();
Session.setattribute ("Strensure", str);

}

And then Web.xml's configuration of the servlet

Copy Code code as follows:

<servlet>
<servlet-name>CheckServlet</servlet-name>
<servlet-class>com.blog.servlet.CheckServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CheckServlet</servlet-name>
<url-pattern>/check</url-pattern>
</servlet-mapping>

Finally, a reference to the JSP page

Copy Code code as follows:

      <title> Verification Code </title>
    <script type= "Text/javascript" language= "JavaScript" >
    //re-obtain validation characters
    function changeimage ()
    {
    Click to trigger the picture overload event to complete the replacement of the picture verification Code
        document.getElementById ("Imgrandom"). src = document.getElementById ("Imgrandom"). src + '? ';
   }
</script>

 
  <body>
     &nbs p;    
          <a href= " Javascript:changeimage (); " > See?</a>
  </body>

In the JSP page, just point the img src attribute to the servlet that generated the captcha, and point to the URL of the Servle map in WEB.XMLT.

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Related Keywords:
jsp vs servlet jsp servlet tutorial jsp sample code references jsp projects with source code verification code php lyft verification code
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