JSP technology

JSP
What is? jsp: It is built on servlet Dynamic web page development technology based on standard .

jsp = java + html + jsp Something about yourself . To write jsp After the document jsp Generate java file , Translate it into class file , There is tomcat Server's work Directory .

JSP notes ：
1.html notes ： It exists everywhere .
2.java notes ： A single , Multiple lines , Documentation Comments . It exists jsp page , Also exist java In the document , Corresponding generated html The file disappears .
3. jsp notes ： <%-- jsp notes –>. There is only jsp page , Generating the corresponding java When you file , It disappears automatically .
page Instructions
page The purpose of the command is to set and jsp Page related information , For example, setting up jsp Page code ,jsp The default language of the page, etc .
Basic grammar ：<%@ page attribute =“ Property value ” attribute =“ Property value ” attribute =“ Property value ” %>

stay jsp Pages usually need to display information from other pages , So you can go through this include Command to include other pages .
Basic grammar ：<%@ include file=“ Of contained files url” %>

Create two jsp page ： date.jsp page ,include.jsp page .
Use jsp Of include The inclusion of an instruction implementation , Also known as static inclusion , The characteristics of static inclusion ：
1. Put the content of multiple pages , Merge output , For example date.jsp and include.jsp Content merge output .
2. Multiple pages will generate one java file , After compiling , Corresponding to one class file .

Implicit objects
Implicit objects are jsp Inside the page ,jsp Provides some objects , You don't have to create it yourself , Objects that can be used directly .
jsp Nine common implicit objects ：
1.request: HttpServletRequest, Request object , It's also a domain object , Scope a request
2.response:HttpServletResponse, The response object
3.session: HttpSession , Conversation object , It's also a domain object , Scope a conversation
4.application:ServletContext, Context object , It's also a domain object , The whole project
5.config:ServletConfig, Configuration object
out:JspWriter, Actually sum PrintWriter It's about the same .
page:Object , On behalf of the current jsp Page objects for
pageContext:PageContext ,jsp Containers
6.exception:Throwable, Exception object , Used to capture exception information . Be careful ： Only current jsp Page has isErrorPage="true" When this property , Can be used exception object .
7.out object ：out Object to output content to the web page , And finally through reponse Buffer for output .
8.pageContext object ： The first function ： Get the other eight implicit objects
9.exception object ： It's used to capture exception information .

jsp:include Action elements ：
Dynamic inclusion
Dynamic inclusion ： Put the content of other resources page , Merge to the current page to be included , Last output .
Basic grammar ：<jsp:include page=“ Of the included page url” flush=“true perhaps false”>jsp:include
Dynamic inclusion features ： The content of multiple pages is merged and output , Multiple jsp Page generation multiple java file , Compile into multiple class file
Static inclusion features ： The content of multiple pages is merged and output , Multiple jsp The page eventually generates a java file , Compile one class file .
Request forwarding
Its function is to forward requests , The effect is equivalent to RequestDispathcer Object's forward Method .
Basic grammar ：<jsp:forward page=“ Forward page's url Address ”></jsp:forward>
Forward page's url Address ： You don't need to carry the project name , Because forwarding is an internal behavior of the server .