Patchca是Piotr Piastucki写的一个java验证码，打包成jar文件发布，patchca简单但功能强大。

pom.xml注入依赖

      <!-- https://mvnrepository.com/artifact/com.github.bingoohuang/patchca -->
        <dependency>
            <groupId>com.github.bingoohuang</groupId>
            <artifactId>patchca</artifactId>
            <version>0.0.1</version>
        </dependency>

CaptchaWordFactory.java

public class CaptchaWordFactory extends RandomWordFactory {

    private String defaultValue = "";

    private boolean isDefaultState = false; // 默认为非固定值状态

    public CaptchaWordFactory() {

        // 文本范围和长度
        characters = "abcdefskmnwx23456789";
        minLength = 4;
        maxLength = 4;
    }

    public CaptchaWordFactory(String defaultValue) {

        this.defaultValue = defaultValue;
        this.isDefaultState = true; //开启绑定值状态 
    }

    public WordBean getNextWord() {


        if(isDefaultState) {
            return new WordBean("","","");
        } else {
            return super.getNextWord();
        }
    }
}

CaptchaService.java

public class CaptchaService extends AbstractCaptchaService {

    private static final Random random = new Random();

    /**
     * 不可定制的验证码服务(默认)
     */
    public CaptchaService() {

        // 文本内容
        wordFactory = new CaptchaWordFactory();

        // 字体
        fontFactory = new RandomFontFactory();

        // 效果
        textRenderer = new BestFitTextRenderer();

        // 背景
        backgroundFactory = new SingleColorBackgroundFactory();

        // 字体颜色
        colorFactory = new SingleColorFactory(new Color(25, 60, 170));

        // 样式(曲线波纹加干扰线)
        //0到4 之间生产随机数
        int i = random.nextInt(5) ;
        switch (i) {
            case 0:
                filterFactory = new CurvesRippleFilterFactory(colorFactory);
                break;
            case 1:
                filterFactory = new DoubleRippleFilterFactory();
                break;
            case 2:
                filterFactory = new WobbleRippleFilterFactory();
                break;
            case 3:
                filterFactory = new DiffuseRippleFilterFactory();
                break;
            case 4:
                filterFactory = new MarbleRippleFilterFactory();
                break;
        }

        // 图片宽高
        width = 150;
        height = 50;
    }

    /**
     * 可以定制的验证码服务(宽度和高度)
     * @param width
     * @param height
     */
    public CaptchaService(int width, int height) {

        // 文本内容
        wordFactory = new CaptchaWordFactory();

        // 字体
        fontFactory = new RandomFontFactory();

        // 效果
        textRenderer = new BestFitTextRenderer();

        // 背景
        backgroundFactory = new SingleColorBackgroundFactory();

        // 字体颜色
        colorFactory = new SingleColorFactory(new Color(25, 60, 170));

        // 样式(曲线波纹加干扰线)
        filterFactory = new CurvesRippleFilterFactory(colorFactory);

        // 图片宽高
        this.width = width;
        this.height = height;
    }

    /**
     * 可以定制的验证码服务(默认值,宽度和高度)
     * @param defaultValue
     * @param width
     * @param height
     */
    public CaptchaService(String defaultValue, int width, int height) {

        // 文本内容
        wordFactory = new CaptchaWordFactory(defaultValue);

        // 字体
        fontFactory = new RandomFontFactory();

        // 效果
        textRenderer = new BestFitTextRenderer();

        // 背景
        backgroundFactory = new SingleColorBackgroundFactory();

        // 字体颜色
        colorFactory = new SingleColorFactory(new Color(25, 60, 170));

        // 样式(曲线波纹加干扰线)
        filterFactory = new CurvesRippleFilterFactory(colorFactory);

        // 图片宽高
        this.width = width;
        this.height = height;
    }
}

利用Controller接收前段Http请求并且以图片资源作响应

CaptchaController.java

@Controller
public class CaptchaController implements Serializable {



    @RequestMapping("/generateCaptcha")
    public void getCaptchaController(HttpServletRequest req, HttpServletResponse res) throws IOException
    {

        // 设置两个响应头
        //返回值类型时 png格式的图片
        res.setContentType("image/png");
        //验证码不要进行缓存
        res.setHeader("cache", "no-cache");

        OutputStream os = res.getOutputStream();

        // 值随机,宽度110px,高度40px
        //可以根据需要修改 参数设置定制化的化的验证码
        CaptchaService captchaService = new CaptchaService(110, 40);

        //生产验证码图片  通过outputStream的方式进行发送
        String captcha = EncoderHelper.getChallangeAndWriteImage(captchaService, "png", os);
        os.flush();

        if(os != null) {
            os.close();
            os = null;
        }
        //将图像的验证码存贮在session 在账号验证时对其进行验证
        req.getSession().setAttribute("captcha", captcha);
    }
    }

jsp部分加入图片标签：

 <tr height="70">
                    <td>验证码</td>
                    <td>
                    <input id="captcha" class="easyui-textbox" name="captcha" class="l_user" />
                    <img id="img" src="generateCaptcha" title="点击刷新" width="60px" height="50px" style="vertical-align:middle;cursor:pointer;" onclick="refreshCode()"/>
                        <span id="errorMsg" style="color:red;margin-left:10px;"></span>
                    </td>
                </tr>

js设置函数用于刷新验证码：

function refreshCode()
{
    var t = (new Date()).getTime();
    var code = "generateCaptcha?k=" + t;
    $("#img").prop("src", code);

}

最终效果：