JSP page directive
The page directive defines attributes that apply to an entire JSP page.
Syntax of JSP page directive
<%@ page attribute="value" %>
Attributes of JSP page directive
o import o contentType
o extends o info o buffer
o language o isELIgnored
o isThreadSafe
o autoFlush
o session
o pageEncoding
o errorPage
o isErrorPage
1)import
The import attribute is used to import class,interface or all the members of a package.It is similar to import keyword in jav class or interface
Example of import attribute
<html>
<body>
<%@ page import="java.util.Date" %>
Today is: <%= new Date() %>
</body>
</html>
2)contentType
The contentType attribute defines the MIME(Multipurpose Internet Mail Extension) type of the HTTP response.The default value is "text/html;charset=ISO-8859-1"
Example of contentType attribute
<html>
<body>
<%@ page contentType=application/msword %>
Today is: <%= new java.util.Date() %>
</body>
</html>
3)extends
The extends attribute defines the parent class that will be inherited by the generated servlet. It is rarely used.
4)info
This attribute simply sets the information of the JSP page is retrieved later by using getServletInfo() method of the Servlet interface.
Example of info attribute
<html>
<body>
<%@ page info="composed by Sonoo Jaiswal" %>
Today is: <%= new java.util.Date() %>
</body>
</html>
The web container will create a method getServletInfo() in the resulting servlet.For example:
public String getServletInfo() { return "composed by Sonoo Jaiswal";
}
5)buffer
The buffer attribute sets the buffer size in kilobytes to handle output generated by the JSP page.The default size of the buffer is 8Kb
Example of buffer attribute
<html>
<body>
<%@ page buffer="16kb" %>
Today is: <%= new java.util.Date() %>
</body>
</html>
6)language
The language attribute specifies the scripting language used in the JSP page. The default value is "java".
7)isELIgnored
We can ignore the Expression Language (EL) in JSP by the isELIgnored attribute. By default, its value is false i.e. Expression Language is enabled by default. We see Expression Language later.
<%@ page isELIgnored="true" %>//Now EL will be ignored
8)isThreadSafe
Servlet and JSP both are multithreaded.
value of isThreadSafe attribute like:
<%@ page isThreadSafe="false" %>
The web container in such a case, will generate the servlet as:
public class SimplePage_jsp extends HttpJspBase implements SingleThreadModel{ ....... }
9)errorPage
The errorPage attribute is used to define the error page, if exception occurs in the current page, it will be redirected to the error page.
Example of errorPage attribute
//index.jsp
<html>
<body>
<%@ page errorPage="myerrorpage.jsp" %>
<%= 100/0 %>
</body>
</html>
10)isErrorPage
The isErrorPage attribute is used to declare that the current page is the error page.
Note: The exception object can only be used in the error page.
Example of isErrorPage attribute
//myerrorpage.jsp
<html>
<body>
<%@ page isErrorPage="true" %>
Sorry an exception occured!<br/>
The exception is: <%= exception %>
</body></html>
Jsp Include Directive
The include directive is used to include the contents of any resource it may be jsp file, html file or text file. The include directive includes the original content of the included resource at page translation time (the jsp page is translated only once so it will be better to include static resource).
Advantage of Include directive
Code Reusability
Syntax of include directive
<%@ include file="resourceName" %>
Example of include directive
In this example, we are including the content of the header.html file. To run this example you must create an header.html file.
<html>
<body>
<%@ include file="header.html" %>
Today is: <%= java.util.Calendar.getInstance().getTime() %>
</body></html>
JSP Taglib directive
The JSP taglib directive is used to define a tag library that defines many tags. We use the TLD (Tag Library Descriptor) file to define the tags. In the custom tag section we will use this tag so it will be better to learn it in custom tag.
Syntax JSP Taglib directive
<%@ taglib uri="uriofthetaglibrary" prefix="prefixoftaglibrary" %>
Example of JSP Taglib directive
In this example, we are using our tag named currentDate. To use this tag we must specify the taglib directive so the container may get information about the tag.
<html>
<body>
<%@ taglib uri="http://www.javatpoint.com/tags" prefix="mytag" %>
<mytag:currentDate/>
</body></html>
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