Operation steps of generating random number verification code by SSH

Time:2021-4-16

1、 login.jsp Page program

Copy codeThe code is as follows:
<script type=”text/javascript”>
function changeValidateCode(obj) {
//Get the current time as a parameter, no specific significance
var timenow = new Date().getTime();
//Each request requires a different parameter, otherwise the same verification code may be returned
//This has something to do with the browser’s caching mechanism. You can also set the page not to cache, so that you don’t need this parameter.
obj.src=”rand.action?d=”+timenow;
}
</script>

Add the following sentence to the form:

Copy codeThe code is as follows:
<s:text name=”random”></s:text>:<s:textfield name=”rand” size=”5″></s:textfield><img src=” rand.action “Onclick =” changevalidatecode (this) “title =” click on the image to refresh the verification code “/ >”

2、 RandomNumUtil.java Class file for generating captcha

Copy codeThe code is as follows:
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;
public class RandomNumUtil {
Private bytearrayinputstream image; / / image
Private string str; / / verification code
private RandomNumUtil(){
Init(); / / initialize properties
}
/*
*Get randomnumutil instance
*/
public static RandomNumUtil Instance(){
return new RandomNumUtil();
}
/*
*Get captcha image
*/
public ByteArrayInputStream getImage(){
return this.image;
}
/*
*Get the captcha of the picture
*/
public String getString(){
return this.str;
}
private void init() {
//Creating images in memory
int width=85, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
//Get graphic context
Graphics g = image.getGraphics();
//Generating random classes
Random random = new Random();
//Set background color
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
//Set font
g.setFont(new Font(“Times New Roman”,Font.PLAIN,18));
//155 interference lines are generated randomly, so that the authentication code in the image is not easy to be detected by other programs
g.setColor(getRandColor(160,200));
for (int i=0;i<155;i++)
{
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x,y,x+xl,y+yl);
}
//Take randomly generated authentication code (6 digits)
String sRand=””;
for (int i=0;i<6;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
//Display the authentication code in the image
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
//The color of the call function is the same, probably because the seed is too close, so it can only be generated directly
g.drawString(rand,13*i+6,16);
}
//Assignment verification code
this.str=sRand;
//Image validation
g.dispose();
ByteArrayInputStream input=null;
ByteArrayOutputStream output = new ByteArrayOutputStream();
try{
ImageOutputStream imageOut = ImageIO.createImageOutputStream(output);
ImageIO.write(image, “JPEG”, imageOut);
imageOut.close();
input = new ByteArrayInputStream(output.toByteArray());
}catch(Exception e){
System.out.println (“error in captcha image generation: + e.tostring());
}
this.image=input ; / * assignment image*/
}
/*
*Get random color in given range
*/
private Color getRandColor(int fc,int bc){
Random random = new Random();
if(fc>255) fc=255;
if(bc>255) bc=255;
int r=fc+random.nextInt(bc-fc);
int g=fc+random.nextInt(bc-fc);
int b=fc+random.nextInt(bc-fc);
return new Color(r,g,b);
}
}

3、 RandomAction.java Action program for generating verification code

Copy codeThe code is as follows:
import java.io.ByteArrayInputStream;
import com.mxl.util.RandomNumUtil;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class RandomAction extends ActionSupport{
private ByteArrayInputStream inputStream;
public String execute() throws Exception{
RandomNumUtil rdnu=RandomNumUtil.Instance();
this.setInputStream ( rdnu.getImage ()); / / get a picture with a random string
ActionContext.getContext ().getSession().put(“random”, rdnu.getString ()); / / get the random string and put it into httpsession
return SUCCESS;
}
public void setInputStream(ByteArrayInputStream inputStream) {
this.inputStream = inputStream;
}
public ByteArrayInputStream getInputStream() {
return inputStream;
}
}

4、 LoginAction.java Action of verification code

Copy codeThe code is as follows:
Private string Rand; / / Rand in the form
public String getRand() {
return rand;
}
public void setRand(String rand) {
this.rand = rand;
}
//Remove from session RandomAction.java The verification code random generated in
String arandom=(String)(ActionContext.getContext().getSession().get(“random”));
//The following is to compare the captcha string saved in session with the captcha string entered by the customer
if(arandom.equals(this.getRand())) {
ActionContext.getContext().getSession().put(“user”, this.getUsername());
return SUCCESS;
}
else {
return ERROR;
}

5. Configuration struts.xml file

Copy codeThe code is as follows:
<! — random captcha — >
<action name=”rand”>
<result type=”stream”>
<param name=”contentType”>image/jpeg</param>
<param name=”inputName”>inputStream</param>
</result>
</action>

6. Generated captcha image demo (6-digit captcha)
explain:
If you want to modify the number of generated captcha, you need to modify the following:
First point:
int width=85, height=20; int width=85, height=20;
Second point: for (int i = 0; I < 6; I + +) for (int i = 0; I < 6; I + +)
Change the number 6 to the number you want to generate

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