What attributes and methods are available for page directives in JSP pages?

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What attributes and methods are available for page directives in JSP pages?

The following author will describe the various attributes of the page directive in JSP, as follows:

The purpose of the page directive

 page directive: used to set various properties of the jsp page no matter where the page directive appears in the jsp page, it acts on the entire jsp page. Usually wePut the page directive at the head of the page

Common attributes of the page directive

<%@page[language="java"][extends="package.class"][import="{package.clas|package.*},..."][contenType="TYPE;charset=CHARSET"][session="True|False"][buffer="none|8kb|sizekb"][autoFlush="True|False"][isThreadSafe="True|False"][info="text"][isErrorPage="True|False"]%>

[language="java"]

Declare the kind of scripting language the JSP page belongs to
java by default

[extends="package.class"]

Set the superclass of the servlet generated by the JSP page. This attribute is generally reserved for developers or providers.
This attribute should be avoided unless referring to a class provided by the server provider specifically for this purpose.

[import="{package.clas|package.*},..."]

Use the import attribute of the page directive to specify the package that the servlet that the JSP page converts into should import
In JSP, the package is absolutely required

Notes:When no package is used, the system considers that the referenced class is in the same package as the current classBy default, servlets import some server-specific packages, for example: java.lang.* javax.servlet.* javax.servlet.jsp.* javax.servlet.http.* is imported at compile timeno need to specifyexample:<%@ page import="package.class" %><%@ page import="package.class1, ..., package.classN" %><%@ page import="java.uti1.*, com.java265.*" %>

[contenType="TYPE;charset=CHARSET"]

The contentType attribute sets the Content-Type response header, indicating the MIME type of the document to be sent to the client program.
The default MIME type is text/html, and the default character set is ISO-8859-1
Example: Modify the contentType:

<%@ page contentType="text/html" %>;Change character set:<%@ page pageEncoding="GBK" %>;Change content type and character set:<%@ page contentType="text/html; charset=utf-8" %>

[session="True|False"]

Set whether the page participates in the HTTP session.The default value is true
If there is an existing session, the predefined variable session (of type HttpSession) should be bound to the existing session;
Otherwise, create a new session and bind it to session
A value of false means no session is created automatically
Access to the variable session causes an error when the JSP page is converted to a servlet
Note that session="false" does not disable session tracking
It just prevents the JSP pageCreate new sessions for users who don't already have sessions

[buffer="none|8kb|sizekb"]

The size of the buffer is used by the out object to cache the executed JSP output to the client browser
none means that there is no cache, and it is directly output to the client browser
The user can specify the buffer'ssize to specify the size of the cache processing, the default value is 8kb

[autoFlush="True|False"]

Controls whether the output buffer should be automatically emptied when the buffer is full (default true)
or throw an exception if the buffer overflows (autoFlush="false")
in buffer="none", the false value is not valid.

[isThreadSafe="True|False"]

Set whether the JSP file is multi-threaded
When this property is set to True, a JSP can handle multiple user requests at the same time. The default value is True.

[info="text"]

Defines a string that can be obtained by the getServletInfo method in the servlet
When the JSP is executed, it is used to describe the relevant information of the current JSP file.

[isErrorPage="True|False"]

Whether to use exception object
Example

<%@pagelanguage="java"import="java.util.*"session="true"contentType="text/html;charset=utf-8"buffer="32kb"%>
JSP page directive