???? 在web系統中,驗證碼的應用基本上隨處可見.驗證碼可以防止他人惡意攻擊和垃圾注冊,可以說已成了web開發中必不可少的環節.遺憾的是,驗證碼在jsp,jsf的組件庫, 至少是一些標準的組件庫中并沒有出現.本文分別介紹如何在jsp和jsf中使用驗證碼和我的一些小經驗,呵呵.
???? 在jsp中,我們使用apache的taglibs-image(http://jakarta.apache.org/taglibs/sandbox/doc/image-doc/intro.html),可以簡便的配置自己的驗證碼.而由于在jsf中,無法和其他jsp標簽庫混用(至少不能和上述標簽庫混用),我們則用Java2D自己繪制驗證碼圖.
?
1. 在jsp中使用taglibs-image部署驗證碼
??? taglibs-image可以通過標簽自動將一段文字和背景圖片生成新的圖片,文字的布局,顏色,字體等等都可以自我定制,因此拿來做驗證碼是非常的簡單
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?? 其中最開始百分號內的java代碼是為了生成驗證碼,然后保存在session中.同時驗證碼和背景圖片生成新的驗證圖.用戶根據此圖輸入驗證碼.在服務器方,只用把用戶提交表單中的驗證碼內容取出和session中保存的驗證碼對比,就可以判斷正確性咯
?????????????
2.JSF
?? jsf中無法使用上述標簽(會無法渲染出來), 因此,我們自己實現一個生成驗證圖的類,再通過jsf的<h:graphicImage>標簽得以顯示.
? 生成驗證碼的java類如下:
package?org.myibm.beans;
import?java.awt.Color;
import?java.awt.Font;
import?java.awt.Graphics;
import?java.awt.image.BufferedImage;
import?java.io.File;
import?java.io.IOException;
import?java.util.Random;
import?javax.imageio.ImageIO;
/**?*//**
?*?用來自動生成驗證圖和驗證碼,驗證圖是背景圖加上干擾點加上驗證碼
?*?
?*?@author?td
?*?
?*/
public?final?class?CodeImageGenerator?
{
????private?final?static?int?DEF_WIDTH?=?60;
????private?final?static?int?DEF_HEIGHT?=?20;
????private?final?static?String?BASE_PATH?=?"validate-images";
????/**?*//**
?????*?驗證碼
?????*/
????private?String?code?=?"";
????/**?*//**
?????*?驗證圖的地址
?????*/
????private?String?path;
????private?int?width;
????private?int?height;
????private?BufferedImage?image;
????/**?*//**
?????*?驗證圖對應的File對象
?????*/
????private?File?target;
????public?CodeImageGenerator()?{
????????this(DEF_WIDTH,?DEF_HEIGHT);
????}
????public?CodeImageGenerator(int?width,?int?height)?{
????????this.width?=?width;
????????this.height?=?height;
????????generateCodeImage();
????}
????/**?*//**
?????*?生成驗證碼和驗證圖
?????*
?????*/
????private?void?generateCodeImage()?{
????????//?create?the?image
????????image?=?new?BufferedImage(width,?height,?BufferedImage.TYPE_INT_RGB);
????????Graphics?g?=?image.getGraphics();
????????//?set?the?background?color
????????g.setColor(new?Color(0xDCDCDC));
????????g.fillRect(0,?0,?width,?height);
????????//?draw?the?border
????????g.setColor(Color.black);
????????g.drawRect(0,?0,?width?-?1,?height?-?1);
????????//?set?the?font
????????g.setFont(new?Font("Times?New?Roman",?Font.PLAIN,?18));
????????//?create?a?random?instance?to?generate?the?codes
????????Random?random?=?new?Random();
????????//?make?some?confusion
????????for?(int?i?=?0;?i?<?50;?i++)?{
????????????int?x?=?random.nextInt(width);
????????????int?y?=?random.nextInt(height);
????????????g.drawOval(x,?y,?0,?0);
????????}?//?generate?a?random?code
????????for?(int?i?=?0;?i?<?4;?i++)?{
????????????String?rand?=?String.valueOf(random.nextInt(10));
????????????code?+=?rand;
????????????g.drawString(rand,?13?*?i?+?6,?16);
????????}
????????g.dispose();
????????try?{
????????????File?dir?=?new?File("K:/Tomcat?5.5/webapps/nirvana/validate-images");
????????????String?s?=?new?Double(Math.random()?*?995596390219L).toString();
????????????File?imgFile?=?new?File(dir,?s?+?".jpeg");
????????????if?(!imgFile.exists())
????????????????imgFile.createNewFile();
????????????target?=?imgFile;
????????????ImageIO.write(image,?"JPEG",?imgFile);
????????????path?=?"/"?+?BASE_PATH?+?"/"?+?s?+?".jpeg";
????????????System.err.println(path);
????????}?catch?(IOException?e)?{
????????????//?TODO?Auto-generated?catch?block
????????????e.printStackTrace();
????????}
????}
????public?BufferedImage?getImage()?{
????????return?image;
????}
????public?String?getCode()?{
????????if?(code?==?null)
????????????code?=?"";
????????return?code;
????}
????public?static?void?main(String[]?args)?throws?Exception?{
????????//?File?imgFile?=?new?File("codeImage.jpeg");
????????//?CodeImageGenerator?cig?=?new?CodeImageGenerator();
????????//?ImageIO.write(cig.getImage(),?"JPEG",?imgFile);
????}
????public?String?getPath()?{
????????return?path;
????}
????public?void?setPath(String?path)?{
????????this.path?=?path;
????}
????/**?*//**
?????*?當這個對象被回收時,同時銷毀其對應的驗證圖
?????*/
????@Override
????protected?void?finalize()?throws?Throwable?{
????????//?TODO?Auto-generated?method?stub
????????//?System.err.println("finalize");
????????if?(target.exists())
????????????target.delete();
????????super.finalize();
????}
????public?File?getTarget()?{
????????return?target;
????}
????public?void?setTarget(File?target)?{
????????this.target?=?target;
????}
}
要說明幾點的事,這個類會把生成的驗證圖放在制定文件夾下,未免得文件越來越多,應該當驗證圖不再使用時將之刪除.所以此類重寫了Object的finalize()方法,當此類被垃圾回收器回收時,同時也刪除其對應的驗證圖.
這樣,就可以利用java的垃圾回收器輕松為我們刪除不用的文件.
另外,在頁面對應的managed-bean中,我們還要添加如何得到驗證碼和驗證圖的方法
private?CodeImageGenerator?validator;
????
????private?String?validate_code;
????
????public?CodeImageGenerator?getValidator()?{
????????if(validator!=null){
????????????validator.getTarget().delete();
????????????validator=null;
????????}
????????validator=new?CodeImageGenerator();
????????System.out.println(validator.getCode());
????????return?validator;
????}
????public?void?setValidator(CodeImageGenerator?validator)?{
????????this.validator?=?validator;
????} 其中validate-code對應用戶輸入的驗證碼信息
因為每次刷新頁面都需要得到不同的驗證碼,所以在getValidator()方法時,每次需要返回一個新的CodeImageGenerator.同時,你可能等不及垃圾回收器幫你刪除文件,因此,可以在這里同時刪除老的驗證圖.
另外,在注冊時我們還需要做一下判斷:
public?String?register()?{
????????//?System.out.println("haha");
????????if(!validator.getCode().equals(validate_code)){
????????????FacesMessage?message?=?new?FacesMessage(
????????????????????FacesMessage.SEVERITY_ERROR,?"驗證碼錯誤",
????????????????????"驗證碼錯誤");
????????????FacesContext.getCurrentInstance().addMessage(null,?message);
????????????FacesContext?fcg?=?FacesContext.getCurrentInstance();
????????????((LoginBean)?fcg.getApplication().getVariableResolver()
????????????????????.resolveVariable(fcg,?"loginBean")).setReg(true);
????????????System.out.println(validator.getCode());
????????????System.out.println(validate_code);
????????????return?null;
????????}
..
} 最后,我們需要在頁面中添加對應的標簽
????????????????????????<h:outputText?value="驗證碼(*)："?styleClass="label"></h:outputText>
????????????????????????<h:message?for="vcode"?styleClass="error"></h:message>
????????????????????????<h:inputText?id="vcode"?required="true"?value="#{myPageBean.validate_code}"></h:inputText>
????????????????????????<h:graphicImage?value="#{myPageBean.validator.path}"></h:graphicImage>
這樣, 我們就在jsf中實現了自己的驗證碼部署^_^
