javaweb利用servlet实现图片验证码
验证码是登录验证的技术,可以一定程度防止恶意脚本刷网站,造成服务器压力。
具体实现思想很简单:
首先利用servlet产生一个随机的验证码, 保存在session中, 然后将它画作图片,输出到浏览器 在登录时对输入的验证码判断即可。
**注意事项:
1.由于struts2会过滤所有action,
在对servlet配置时,不能配置为与action类似的名称,需要为name.ssss;ssss可以是其他,不能是action.
2.对验证码图片的点击刷新,由于直接使用onclick事件对图片的src刷新,是行不通的,
因为浏览器会认为即使你刷新,他也只是将已经生成的图片再一次发送给你,看起来验证码是没有变得。
那么你就需要一个变化的参数跟着src后即可,例如随机数(不好,随后体验,在访问量一定程度后就无法了,因为重叠程度大,不一定会刷新),时间戳等,就好了
**
代码:
参生验证码图片的servlet
步骤
// 图片格式
// 设置浏览器不要缓存此图片
// 创建内存图像并获得图形上下文(BufferedImage)
// 画图片
//输出图片
{ServletOutputStream sos = resp.getOutputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(image, “JPEG”, baos);
byte[] buffer = baos.toByteArray();
resp.setContentLength(buffer.length);
sos.write(buffer);
baos.close();
sos.close();}
package servlet.checkcode;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.ByteArrayOutputStream;import java.io.IOException;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;@WebServlet(name = "code", value = "/code.servlet")public class Code extends HttpServlet {/*** @author joker 验证码servlet*/private static final long serialVersionUID = -1139461793398415115L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// TODO 自动生成的方法存根this.doPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// TODO 自动生成的方法存根HttpSession session=req.getSession(true);resp.setContentType("image/jpeg");// 图片格式// 设置浏览器不要缓存此图片resp.setHeader("Pragma", "No-cache");resp.setHeader("Cache-Control", "no-cache");resp.setDateHeader("Expires", 0);// 创建内存图像并获得图形上下文int width = 85;int height = 30;BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);Graphics graphics = image.getGraphics();// 验证码String table = "0123456789QWERTYUIOPASDFGHJKLZXCVBNMzxcvbnmasdfghjklqwertyuiop";char code[] = new char[4];for (int i = 0; i < 4; i++) {int rand = (int) (Math.random() * (table.length() - 1));code[i] = table.charAt(rand);}// 画背景graphics.setColor(Color.getHSBColor(211, 211, 211));graphics.fillRect(0, 0, width, height);graphics.setColor(Color.BLACK);graphics.setFont(new Font("", 1, 20));graphics.drawLine(0, 17, width, 23);if (code[0] <= 69) {graphics.setColor(Color.BLUE);graphics.drawLine(0, 8, width, 28);} else if (code[2] >= 90) {graphics.setColor(Color.RED);graphics.drawLine(0, 28, width, 15);}else if (code[3] >= 111) {graphics.setColor(Color.black);graphics.drawLine(0, 28, width, 15);}// 画验证码graphics.drawString("" + code[0], 2, 20);graphics.setColor(Color.YELLOW);graphics.drawString(" " + code[1], 20, 23);graphics.setColor(Color.RED);graphics.drawString(" " + code[2], 40, 20);graphics.setColor(Color.BLACK);graphics.drawString(" " + code[3], 60, 25);// 将图像传到客户端ServletOutputStream sos = resp.getOutputStream();ByteArrayOutputStream baos = new ByteArrayOutputStream();ImageIO.write(image, "JPEG", baos);byte[] buffer = baos.toByteArray();resp.setContentLength(buffer.length);sos.write(buffer);baos.close();sos.close();// 验证session.setAttribute("truecode", ""+code[0]+code[1]+code[2]+code[3]);}@Overridepublic void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException {// TODO 自动生成的方法存根super.service(arg0, arg1);}}
前端:
<s:textfield name=“code” title=“请输入验证码”></s:textfield>
登录验证的action:
package controller.login;import org.apache.struts2.ServletActionContext;import com.opensymphony.xwork2.ActionSupport;import model.linkdbm.JDBC_DBM;public class Login_db extends ActionSupport {/*** @author joker* * action* 验证登录*/private static final long serialVersionUID = 6346619400337792820L;public String user;public String pass;public String code;//验证码public String getCode() {return code;}public void setCode(String code) {this.code = code;}public String getUser() {return user;}public void setUser(String user) {this.user = user;}public String getPass() {return pass;}public void setPass(String pass) {this.pass = pass;}public String execute() throws Exception {String truecode=(String) ServletActionContext.getRequest().getSession().getAttribute("truecode");//登录验证码验证if(!code.equals(truecode)) {this.addFieldError("user", "输入的验证码有误!!!");return INPUT;}boolean oginflag=true;if (loginflag) {this.addFieldError("user", "登录成功");return SUCCESS;} else {this.addFieldError("user", "账号或密码错误!!!");return INPUT;}}@Overridepublic void validate() {// TODO 自动生成的方法存根if (user == null || user.trim().equals("")) {this.addFieldError("user", "用户名不能为空");return;}if (pass == null || pass.trim().equals("")) {this.addFieldError("pass", "密码不能为空");}}}
如果觉得《javaweb利用servlet与struts2实现可点击刷新的基础图片验证码》对你有帮助,请点赞、收藏,并留下你的观点哦!