SimpleCaptcha based verification code open source project - introduction to kaptcha verification code component

Kaptcha is an open source project based on SimpleCaptcha's verification code.

Kaptcha is more convenient to use, just add the jar package dependency and simply configure it to use. All kaptcha configurations can be done via web.xml. If Spring MVC is used in your project, there is another way to do this.

First, a simple jsp-servlet project 1. Add jar package dependencies

If you use maven to centrally manage jar packages, add dependency to the project's pom.xml

Xml code

"! -- kaptcha --"

Dependency

"groupId" com.google.code.kaptcha"/groupId"

"arTIfacTId" kaptcha "/arTIfacTId"

"version" 2.3.2 "/version"

/dependency

"! -- kaptcha --"

Dependency

"groupId" com.google.code.kaptcha"/groupId"

"artifactId" kaptcha "/artifactId"

"version" 2.3.2 "/version"

/dependency

If it is a non-maven managed project, download the kaptcha jar package directly on the official website and add it to the project lib library.

2. Configure web.xml

As mentioned above, kaptcha is configured in web.xml. We must configure kaptcha servlet in web.xml, as follows:

Xml code

Servlet

"servlet-name" Kaptcha "/servlet-name"

Servlet-class com.google.code.kaptcha.servlet.KaptchaServlet/servlet-class

/servlet

Servlet-mapping

"servlet-name" Kaptcha "/servlet-name"

"url-pattern"/kaptcha.jpg "/url-pattern"

/servlet-mapping

Servlet

"servlet-name" Kaptcha "/servlet-name"

Servlet-class com.google.code.kaptcha.servlet.KaptchaServlet/servlet-class

/servlet

Servlet-mapping

"servlet-name" Kaptcha "/servlet-name"

"url-pattern"/kaptcha.jpg "/url-pattern"

/servlet-mapping

The url-pattern of the servlet can be customized.

All of kaptcha's parameters have a default configuration, and if we don't display the configuration, the default configuration will be taken.

If you want to display the configuration kaptcha, when configuring the Servlet corresponding to kaptcha, add the parameter configuration of the response in init-param. An example is as follows:

Xml code

Servlet

"servlet-name" Kaptcha "/servlet-name"

Servlet-class com.google.code.kaptcha.servlet.KaptchaServlet/servlet-class

Init-param

"param-name" kaptcha.image.width "/param-name"

Param-value 200/param-value

Description Width in pixels of the kaptcha image. "/description"

"/init-param"

Init-param

"param-name" kaptcha.image.height "/param-name"

Param-value 50/param-value

Description "Height in pixels of the kaptcha image." /description

"/init-param"

Init-param

"param-name" kaptcha.textproducer.char.length "/param-name"

"param-value" 4 "/param-value"

"Description" The number of characters to display. "/description"

"/init-param"

Init-param

"param-name" kaptcha.noise.impl "/param-name"

"param-value" com.google.code.kaptcha.impl.NoNoise "/param-value"

Description "The noise producer. "/description"

"/init-param"

/servlet

Servlet

"servlet-name" Kaptcha "/servlet-name"

Servlet-class com.google.code.kaptcha.servlet.KaptchaServlet/servlet-class

Init-param

"param-name" kaptcha.image.width "/param-name"

Param-value 200/param-value

Description Width in pixels of the kaptcha image. "/description"

"/init-param"

Init-param

"param-name" kaptcha.image.height "/param-name"

Param-value 50/param-value

Description "Height in pixels of the kaptcha image." /description

"/init-param"

Init-param

"param-name" kaptcha.textproducer.char.length "/param-name"

"param-value" 4 "/param-value"

"Description" The number of characters to display. "/description"

"/init-param"

Init-param

"param-name" kaptcha.noise.impl "/param-name"

"param-value" com.google.code.kaptcha.impl.NoNoise "/param-value"

Description "The noise producer. "/description"

"/init-param"

/servlet

3. Page call

Html code

Formaction=“submit.action”

Inputtype=“text”name=”kaptcha”value=””/”imgsrc=“kaptcha.jpg”/

/form

"form action="submit.action"

"input type="text" name=“kaptcha” value=”” /”img src=“kaptcha.jpg” /》

/form

4. Verify the code in the submit action method

Java code

/ / From the session to extract the verification code text value generated by the servlet

String kaptchaExpected = (String)request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);

/ / Get the verification code entered on the user page

String kaptchaReceived = request.getParameter("kaptcha");

/ / Verify that the verification code is correct

If (kaptchaReceived == null || !kaptchaReceived.equalsIgnoreCase(kaptchaExpected)){

setError("kaptcha", "Invalid validation code.");

}

/ / From the session to extract the verification code text value generated by the servlet

String kaptchaExpected = (String)request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);

/ / Get the verification code entered on the user page

String kaptchaReceived = request.getParameter("kaptcha");

/ / Verify that the verification code is correct

If (kaptchaReceived == null || !kaptchaReceived.equalsIgnoreCase(kaptchaExpected)){

setError("kaptcha", "Invalid validation code.");

}

Note: Make sure the JDK is set to -Djava.awt.headless=true

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