Introduction to JSP

My first JSP file is a very simple JSP file, as shown below:

<% @ Pageimport = "java. util. Date" %> <% @ Page language = "java" contentType = "text/html; charset = UTF-8" PageEncoding = "UTF-8" %> JSP <% = "Hello" %>

I am using the Tomcat7.0 server. After being loaded to Eclipse, I will compile the JSP file above and compile the JSP file into

Servlet java files, such:

Package org. apache. jsp; Import javax. servlet .*; Import javax. servlet. http .*; Import javax. servlet. jsp .*; Import java. util. Date; Public final class index_jsp extends org. apache. jasper. runtime. HttpJspBase Implements org. apache. jasper. runtime. JspSourceDependent { Private static final javax. servlet. jsp. JspFactory _ jspxFactory = Javax. servlet. jsp. JspFactory. getdefafactory Factory (); Private static java. util. Map _ Jspx_dependants; Private javax. el. ExpressionFactory _ el_expressionfactory; Private org. apache. tomcat. InstanceManager _ jsp_instancemanager; Public java. util. Map GetDependants (){ Return _ jspx_dependants; } Public void _ jspInit (){ _ El_expressionfactory = _ jspxFactory. getJspApplicationContext (getServletConfig (). getServletContext (). getExpressionFactory (); _ Jsp_instancemanager = org. apache. jasper. runtime. InstanceManagerFactory. getInstanceManager (getServletConfig ()); } Public void _ jspDestroy (){ } Public void _ jspService (final javax. servlet. http. HttpServletRequest request, final javax. servlet. http. HttpServletResponse response) Throws java. io. IOException, javax. servlet. ServletException { Final javax. servlet. jsp. PageContext pageContext; Javax. servlet. http. HttpSession session = null; Final javax. servlet. ServletContext application; Final javax. servlet. ServletConfig config; Javax. servlet. jsp. JspWriter out = null; Final java. lang. Object page = this; Javax. servlet. jsp. JspWriter _ jspx_out = null; Javax. servlet. jsp. PageContext _ jspx_page_context = null; Try { Response. setContentType ("text/html; charset = UTF-8 "); PageContext = _ jspxFactory. getPageContext (this, request, response, Null, true, 8192, true ); _ Jspx_page_context = pageContext; Application = pageContext. getServletContext (); Config = pageContext. getServletConfig (); Session = pageContext. getSession (); Out = pageContext. getOut (); _ Jspx_out = out; Out. write ("\ r \ n "); Out. write ("\ r \ n "); Out. write ("\ R \ n "); Out. write ("\ R \ n "); Out. write ("\ R \ n "); Out. write (" \ R \ n "); Out. write ("JSP\ R \ n "); Out. write ("\ R \ n "); Out. write ("\ R \ n "); Out. print ("hello "); Out. write ("\ r \ n "); Out. write ("\ R \ n "); Out. write (""); } Catch (java. lang. Throwable t ){ If (! (T instanceof javax. servlet. jsp. SkipPageException )){ Out = _ jspx_out; If (out! = Null & out. getBufferSize ()! = 0) Try {out. clearBuffer ();} catch (java. io. IOException e ){} If (_ jspx_page_context! = Null) _ jspx_page_context.handlePageException (t ); Else throw new ServletException (t ); } } Finally { _ JspxFactory. releasePageContext (_ jspx_page_context ); } } }

We can see that the JSP file is indeed compiled into a java file on the backend server. We only pay attention to the content we write on the JSP page, but do not pay attention to the parsing of html tags.

// The JSP file will be compiled into a class named index_jsp by the jsp file name (My jsp file name is index. jsp)

Public final class index_jsp extends org. apache. jasper. runtime. HttpJspBase

Implements org. apache. jasper. runtime. JspSourceDependent {

// A parser that generates a JSP file in factory Mode

Private static final javax. servlet. jsp. JspFactory _ jspxFactory =

Javax. servlet. jsp. JspFactory. getdefafactory Factory ();

// Call the initialization method to obtain JSP parameters through global context

Public void _ jspInit (){

_ El_expressionfactory = _ jspxFactory. getJspApplicationContext (getServletConfig (). getServletContext (). getExpressionFactory ();

_ Jsp_instancemanager = org. apache. jasper. runtime. InstanceManagerFactory. getInstanceManager (getServletConfig ());

}

// The thread will be destroyed after compilation.

Public void _ jspDestroy (){

}

// The core is the complete parsing of JSP files.

Response. setContentType ("text/html; charset = UTF-8 ");

PageContext = _ jspxFactory. getPageContext (this, request, response,

Null, true, 8192, true );

_ Jspx_page_context = pageContext;

Application = pageContext. getServletContext ();

Config = pageContext. getServletConfig ();

Session = pageContext. getSession ();

Out = pageContext. getOut ();

_ Jspx_out = out;

// The parsed content

Out. write ("\ r \ n ");

Out. write ("\ r \ n ");

Out. write ("\ R \ n ");

Out. write ("\ R \ n ");

Out. write ("\ R \ n ");

Out. write (" \ R \ n ");

Out. write ("JSP\ R \ n ");

Out. write ("\ R \ n ");

Out. write ("\ R \ n ");

Out. print ("hello ");

Out. write ("\ r \ n ");

Out. write ("\ R \ n ");

Out. write ("");