1. JSP concept
JSP full name: Java Server Pages (dynamic web development technology, also called JAVA server page), which is essentially a simplified Servlet design. It embeds the JAVA language in the traditional HTML language to form a JSP file, and its suffix is in the form of .jsp.
2, JSP page composition
JSP pages consist of static content (HTML), script programs, JSP declarations, expressions, comments, directives, etc.
2.1 Static content: It is the static text of the JSP page content, which is HTML text.
2.2 Script: It can contain arbitrary Java statements, variables, methods, expressions. Its grammatical format is to embed the Java statement segment into <% %>,
For example: <% System.out.println(100/0) ; %> Don't forget the semicolon after the statement segment.
2.3 JSP declaration: A declaration statement can declare one or more variables, and the method is used by the following Java code. In JSP, it must be declared before use.
For example: < % !int i=1; %> , < % ! %> is equivalent to defining a global variable. An exclamation mark is equivalent to defining a global variable. <%%> is equivalent to defining a local variable.
2.4 Expression: The format is as follows:
<%=expression body%>, for example: <%=page.toString%>, do not add a semicolon at the end of the expression.
2.5 Comment: <% --Comment--%>, the comment format in HTML is: <% !--Comment--%>
2.6 Instructions: Instructions in JSP are used to set relevant properties of the entire page. The syntax format is: <% directive attribute = "value"%>
1. <% @ page ...%> defines the dependency properties of the page, such as scripting language, error page, and cache requirements.
2. <% @include...%> includes other files
3. <% @taglib...%> introduces the definition of the tag library, which can be a custom tag.