spring mvc 使用kaptcha配置生成验证码实例

<dependency>
  <groupid>com.google.code.kaptcha</groupid>
  <artifactid>kaptcha</artifactid>
  <version>2.3</version>
  <classifier>jdk15</classifier>
</dependency>

<bean id="verifycodeproducer" class="com.google.code.kaptcha.impl.defaultkaptcha">
    <property name="config">
      <bean class="com.google.code.kaptcha.util.config">
        <constructor-arg>
          <props>
            <prop key="kaptcha.border">yes</prop>
            <prop key="kaptcha.border.color">105,179,90</prop>
            <prop key="kaptcha.border.thickness">1</prop>

            <prop key="kaptcha.noise.color">blue</prop>

            <prop key="kaptcha.image.width">150</prop>
            <prop key="kaptcha.image.height">50</prop>

            <prop key="kaptcha.session.key">verifycode</prop>

            <!-- <prop key="kaptcha.textproducer.char.string">0123456789abcdefghijklmnopqrst!@#$%^*</prop> -->
            <prop key="kaptcha.textproducer.char.length">4</prop>
            <prop key="kaptcha.textproducer.char.space">4</prop>


            <prop key="kaptcha.textproducer.font.size">30</prop>
            <prop key="kaptcha.textproducer.font.color">blue</prop>

          </props>
        </constructor-arg>
      </bean>
    </property>
  </bean>

@controller
public class commoncontroller {

  @autowired
  private producer verifycodeproducer;

  @requestmapping(path = "/getverifycodeimage", method = requestmethod.get)
  public void getverifycodeimage(httpservletrequest request, httpservletresponse response) {
    httpsession session = request.getsession();

    responseutils.nocache(response);
    response.setcontenttype("image/jpeg");

    string captext = verifycodeproducer.createtext();
    session.setattribute(constants.session_key_verify_code, captext);

    bufferedimage bi = verifycodeproducer.createimage(captext);
    servletoutputstream out = null;
    try {
      out = response.getoutputstream();
      imageio.write(bi, "jpg", out);
      out.flush();
    } catch (exception ex) {
      logger.error("failed to produce the verify code image: ", ex);
      throw new serverinternalexception("cannot produce the verify code image.");
    } finally {
      ioutils.closequietly(out);
    }
  }
}

<div class="form-group has-feedback">
  <span class="glyphicon glyphicon-barcode form-control-feedback"></span> 
  <input id="verifycode" name="verifycode" type="text" maxlength="4" class="form-control" placeholder="<spring:message code='login.label.code' />" />
  <div style="height: 1px"></div>
  <img src="${pagecontext.request.contextpath}/getverifycodeimage" id="verifycodeimage" style="margin-bottom: -3px" /> 
  <a href="#" rel="external nofollow" onclick="changeverifycode()"><spring:message code='login.code.tip' /></a>
</div>

function changeverifycode() {
  $('#verifycodeimage').hide().attr('src', '${pagecontext.request.contextpath}/getverifycodeimage?' + math.floor(math.random()*100) ).fadein(); 
  event.cancelbubble=true; 
}