Head First Servlets & JSP learning note Seventh--as a JSP

<%@.%> This is an instruction .

<%@ page ... import= "java.util.Date"%> This is the page directive , import is a property of the page directive

<%.%> This is scriptlet, Inside is pure Java code, need semicolon end

<% = ...%> this is an expression , the expression does not end with a semicolon; You must never use a method with a return type of void as an expression

The JSP is transformed by the Web container and a servlet is generated:

The contents of the scriptlet and expressions in the JSP are placed in the servlet's service () method, and therefore are local variables.

so , how do you declare the member variables and methods of the Servlet class? The answer is:JSP declaration

<%! ...%> this is the JSP declaration. For example <%! int count = 0;%>

The JSP declaration uses an exclamation point, followed by a semicolon ending.

To configure the servlet initialization parameters for the JSP:

1 <Web-app>2     <servlet>3         <Servlet-name>Mytestinit</Servlet-name>4         <Jsp-file>/testinit.jsp</Jsp-file> //This is different from the regular servlet 5         <Init-param>6             <Param-name>Email</Param-name>7             <Param-value>[Email protected]</Param-value>8         </Init-param>9     </servlet>Ten      One     <servlet-mapping>//When you define a servlet for a JSP, you must also define a servlet mapping for the JSP page A         <Servlet-name>Mytestinit</Servlet-name> -         <Url-pattern>/testinit.jsp</Url-pattern> -     </servlet-mapping> the </Web-app>

Overwrite the Jspinit () method: (This method is called by the servlet's init () method)

1  Public void Jspinit () {  //Use JSP declaration to overwrite Jspinit () method  2     servletconfig SCG =  Getservletconfig (); 3     String emailaddr = scg.getinitparameter ("email"); 4     5     ServletContext SCT = getservletcontext (); 6     Sct.setattribute ("Mail", emailaddr); 7 }

JSP adds a scope to the page scope:

The standard servlet scopes are three: request, session, application (context) scope;

JSP added page scope (PageContext)

In a JSP, you use 4 implicit objects to get and set properties: servlet in

	jsp (Implicit object)	jsp (Implicit object)
Request scope (Request)	Request.set Attribute ("foo", Object);	request.setattribute ("foo", Object);	request.getattribute ("foo");
Session scope (session)	request.getsession (). SetAttribute ("foo", Object);	session.setattribute ("foo", Object);	session.getattribute ("foo");
Apply scope (context)	getservletcontext (). SetAttribute ("foo", Object);	application.setattribute ("foo", Object);	application.getattribute ("foo");
page scope (pagecontext)	Not applicable	pagecontext.setattribute ("foo", Object);	pagecontext.getattribute ("foo");

JSPs can also be used by PageContext to get the properties of any scope, and to set the properties of any scope:

1. Set a session-scoped property: <% pagecontext.setattribute ("foo", Object, Pagecontext.session_scope); %>

2. Set an Application scope property: <% pagecontext.setattribute ("foo", Object, Pagecontext.application_scope); %>

3. Get an Application scope property: <% pagecontext.getattribute ("foo", Pagecontext.application_scope); %>

There are three types of directives:

Page directive, taglib directive, include directive

Disable script elements in JSP: (only this method)

1 <Web-app>2     <Jsp-config>3         <Jsp-property-group>4             <Url-pattern>*.jsp</Url-pattern>5             <Scripting-invalid> //This tag lets JSP prohibit the use of script elements 6 true7             </Scripting-invalid>8         </Jsp-property-group>9     </Jsp-config>Ten </Web-app>

Ignore El in JSP:

method One : Specify in Web. xml:

1 <Web-app>2     <Jsp-config>3         <Jsp-property-group>4             <Url-pattern>*.jsp</Url-pattern>5             <el-ignored> //This flag indicates that the EL is ignored 6 true7             </el-ignored>8         </Jsp-property-group>9     </Jsp-config>Ten </Web-app>

method Two : or through the page directive:

<%@ page iselignored= "true"%>

Actions-standard and non-standard actions:

1 <  page= "wickedfooter.jsp"/>  //Standard action 　　 2<  var= "rate"  value= "/>" //non-standard action 

Head First Servlets & JSP learning note Seventh--as a JSP