EL XI built-in objects

This is a built-in objects can directly use it, do not need to go to the statement.

1, reads the page context:

(1) pageContext objects:

Gets a URL and URI:

<body>
URI:${pageContext.request.requestURI};<br>
URL:${pageContext.request.requestURL};<br>
</body>

application:

Gets the name of the dynamic web application:

<body>
${pageContext.request.contextPath}

</body>

Operating results for the name of the web application.

<center>
    <h3>注册</h3>
    <form action="${pageContext.request.contextPath}/el.jsp" method="post">
        用户名:<input type="text" name="account" size="12"><br><br>
        密码:<input type="password" name="password" size="12">
        <input type="submit" value="注册">
        <input type="reset" value="取消">
    </form>
</center>

Put it into action, even if the project name is changed, is still able to function properly.

Which pageContext.request to get the request object.

2, four domains (not an object):

（2）pageContext域，(3)request域，(4)session域，(5)application域：pageScrop、requestScrop、sessionScrop、applicationScrop。

3, read client form or query string parameters:

(6) param: get a single parameter:

Gets the data:

<body bgcolor="aqua">
<center>
    <h3>注册</h3>
    <form action="${pageContext.request.contextPath}/el.jsp" method="post">
        用户名:<input type="text" name="account" size="12"><br><br>
        密码:<input type="password" name="password" size="12">
        <input type="submit" value="注册">
        <input type="reset" value="取消">
    </form>
</center>

<body> 
account name: $ {param.account} 
Password: $ {param.password}
 </ body>

(7) paramValues get form data.

4: the read request request header:

(8) header: acquiring a single data:

</head>
<body bgcolor="#7fffd4">
${header["User-Agent"]}<br>
${header.Host}
</body>

(9) headerValues: acquiring a plurality of data.

5: reading (10) Cookie:

(1) create a JSP to create a Cookie:

<body>
<%
Cookie cookie=new Cookie("name","zhai");
response.addCookie(cookie);
%>
</body>

(2) obtain information in the Cookie:

${cookie.name.value}

6, reads initialization parameters:

(1) first initialization data arranged in 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">
    <context-param>
        <param-name>zhai</param-name>
        <param-value>1997</param-value>
    </context-param>
</web-app>

(2) to obtain:

<body bgcolor="#7fffd4">
${initParam.zhai}
</body>

EL XI built-in objects

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