simplecaptchaservlet.java

一个为 Java/J2EE生成的最简化CAPTCHA的框架

package nl.captcha.servlet;

import static nl.captcha.Captcha.NAME;

import java.awt.Color;
import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import nl.captcha.Captcha;
import nl.captcha.backgrounds.FlatColorBackgroundProducer;
import nl.captcha.gimpy.ShearGimpyRenderer;
import nl.captcha.noise.StraightLineNoiseProducer;


/**
 * Generates, displays, and stores in session a 200x50 CAPTCHA image with sheared black text, 
 * a solid dark grey background, and a straight, slanted red line through the text.
 * 
 * @author <a href="mailto:[e-mail]">James Childers</a>
 */
public class SimpleCaptchaServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private static final int IMG_WIDTH = 200;
    private static final int IMG_HEIGHT = 50;

    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

        Captcha captcha = new Captcha.Builder(IMG_WIDTH, IMG_HEIGHT)
        	.addText()
            .addBackground(new FlatColorBackgroundProducer(Color.WHITE))
            .gimp(new ShearGimpyRenderer())
            .addNoise(new StraightLineNoiseProducer())
            .build();

        CaptchaServletUtil.writeImage(resp, captcha.getImage());
        req.getSession().setAttribute(NAME, captcha);
    }
}