ssh generates a random number captcha operation step

1. login.jsp page program

 
<script type="text/javascript"> 
function changeValidateCode(obj) { 
// Gets the current time as a parameter  
var timenow = new Date().getTime(); 
// Each request requires 1 Two different arguments, otherwise the same captcha might be returned  
// This has to do with the browser's caching mechanism. You can also set the page to not be cached so that you don't have to use this parameter.  
obj.src="rand.action?d="+timenow; 
} 
</script> 

Add the following sentence to the form:

 
<s:text name="random"></s:text> : <s:textfield name="rand" size="5"></s:textfield><img src="rand.action" onclick="changeValidateCode(this)" title=" Click the image to refresh the captcha "/> 

2. RandomNumUtil.java class file for generating captcha

 
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();// Initialization property  
} 
/* 
*  achieve RandomNumUtil The instance  
*/ 
public static RandomNumUtil Instance(){ 
return new RandomNumUtil(); 
} 
/* 
*  Get the captcha image  
*/ 
public ByteArrayInputStream getImage(){ 
return this.image; 
} 
/* 
*  Get the captcha of the image  
*/ 
public String getString(){ 
return this.str; 
} 
private void init() { 
//  Create an image in memory  
int width=85, height=20; 
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); 
//  Get graphic context  
Graphics g = image.getGraphics(); 
//  Generate random class  
Random random = new Random(); 
//  Setting the background color  
g.setColor(getRandColor(200,250)); 
g.fillRect(0, 0, width, height); 
//  Set the font  
g.setFont(new Font("Times New Roman",Font.PLAIN,18)); 
//  Randomly generated 155 Interference line, so that the authentication code in the image is not easily 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 the randomly generated authentication code (6 A digital ) 
String sRand=""; 
for (int i=0;i<6;i++){ 
String rand=String.valueOf(random.nextInt(10)); 
sRand+=rand; 
//  Displays the authentication code in the image  
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110))); 
//  Call the function out of the same color, perhaps because the seed is too close, so can only be generated directly  
g.drawString(rand,13*i+6,16); 
} 
// Assign captcha  
this.str=sRand; 
// The image effect  
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: "+e.toString()); 
} 
this.image=input;/*  Assignment image  */ 
} 
/* 
*  Get a random color for a 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 that generates captcha

 
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());// Gets a picture with a random string  
ActionContext.getContext().getSession().put("random", rdnu.getString());// Get a random string and put it in HttpSession 
return SUCCESS; 
} 
public void setInputStream(ByteArrayInputStream inputStream) { 
this.inputStream = inputStream; 
} 
public ByteArrayInputStream getInputStream() { 
return inputStream; 
} 
} 

4. LoginAction.java verification code action

 
private String rand; // In the form rand 
public String getRand() { 
return rand; 
} 
public void setRand(String rand) { 
this.rand = rand; 
} 
// from session Remove the RandomAction.java  The captcha generated in random 
String arandom=(String)(ActionContext.getContext().getSession().get("random")); 
// So here's how session Save the captcha string in compare to 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. Configure the struts.xml file

 
<!-- Random Verification code  --> 
<action name="rand" class="com.mxl.rand.RandomAction"> 
<result type="stream"> 
<param name="contentType">image/jpeg</param> 
<param name="inputName">inputStream</param> 
</result> 
</action> 

6. Picture demonstration of generated verification code (implemented six-digit verification code)
Description:
If you want to modify the number of captcha generated, you need to modify the following:
Point 1:
int width=85, height=20; int width=85, height=20;
Point 2: 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