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                        /Java實現驗證碼制作

校驗驗證碼是否正確的頁面一片空白，無法顯示校驗結果true

check.jsp

<%--
??Created?by?IntelliJ?IDEA.
??User:?ASUS
??Date:?2019/9/11
??Time:?14:53
??To?change?this?template?use?File?|?Settings?|?File?Templates.
--%>
<%@?page?contentType="text/html;charset=UTF-8"?language="java"?%>
<html>
<head>
????<title>校驗頁</title>
</head>
<body>
<%
????String?k?=?(String)session.getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
????String?str?=?request.getParameter("r");
????if(k.equals(str)){
????????System.out.println("true");
????????System.out.println(k+"..."+str);
????}
%>

</body>
</html>

index.jsp

<%--
??Created?by?IntelliJ?IDEA.
??User:?ASUS
??Date:?2019/9/11
??Time:?14:42
??To?change?this?template?use?File?|?Settings?|?File?Templates.
--%>
<%@?page?contentType="text/html;charset=UTF-8"?language="java"?%>
<html>
??<head>
????<title>驗證碼</title>
??</head>
??<body>
??<form?action="/check.jsp"??method="post">
??<img?src="/randomcode.jpg">
??<input?type="text"?name="r">
??<input?type="submit">
??</form>
??</body>
</html>

web.xml

<?xml?version="1.0"?encoding="UTF-8"?>
<web-app?xmlns="http://xmlns.jcp.org/xml/ns/javaee"
?????????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
?????????xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee?http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
?????????version="4.0">
????<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>/randomcode.jpg</url-pattern>
????</servlet-mapping>

</web-app>