Java Fundamentals Chapter 14th (servlet declaration cycle, Servlet provides data to JSP, servlet jump JSP, JSP writes Java code)

One, servlet declaration cycle

The 1.Servlet declaration cycle is generally divided into four steps: Load, instantiate, service, destroy.

2. Instantiation is performed only once throughout the life cycle.

Second, JSP

1.Servlet providing data to the JSP

Request.setattribute (,);

Example: Request.setattribute ("Key", "Hello");

2.Servlet Jump JSP

(1) Same request method: Request.getrequestdispatcher ("/path"). Forward (request, response);

The request jump can only be requested in the same way.

(2) Different request method: Response.sendredirect ("path");

The address bar will change after execution.

Write Java code in 3.jsp

(1) <%=%>

Can only write expressions, variable values

Example: <%= 1 + 1%>

<%= Request.getattribute ("Hello")%>

(2) <%

code block;

%>

Example: <%

String value = (string) request.getattribute ();

%>

4.HttpSession session = Request.getsession ();

Session.setattribute (,);

Can be under the same request, or under different requests, but in the same browser window.

Example: String value = (string) session.getattribute ("");

5.servletContext sc = Session.getservletcontext ();

Sc.setattribute (,);

You can also be under different browsers under the same request and at different requests.

String value = (string) application.getattribute ("");

Java Fundamentals Chapter 14th (servlet declaration cycle, Servlet provides data to JSP, servlet jump JSP, Java code written in JSP)