4 basic syntax for JSP

1. JSP annotations

2. JSP Declaration

3. JSP expression

4. JSP Script

JSP Comments:

Comment Format:

<%--Comment Content--%>

Note that the comments of the JSP are not exported to HTML.

JSP declaration:

JSP declarations are used to declare variables and methods. Declaring a method in a JSP declaration looks special, and it seems that you can define a method without defining a class, and that the method seems to exist independently from the class.

In fact, the JSP declaration will be converted into a member variable or method of the corresponding Servlet.

Declaration syntax: (using the <%! ...%> "This format, the first percent sign after a"! ")

<%!//declares an integer variable public int count;//declares a method public String info () {    return "Browse Times:" + count;} %>

　　

JSP expression:

The output expression cannot be followed by a semicolon <%= expression%><%=count++%><%=info ()%>

Open multiple browsers, we will find that the value of the count variable is continuous because the JSP page is compiled into a Servlet instance,
Each Servlet has only one instance in the container; the variable declared in the JSP is a member variable, and the member variable is initialized only when the instance is created.
The value of the variable is persisted until the instance is destroyed.

JSP script:

In general, all executable Java code can be embedded in an HTML page through a JSP script.

For example, output a list

<ul>    <% for    (int i = 0; i < 3; i++) {    %>        <li><%=i%></li>    <%    }    %></ul>

　　

We can look at the compiled Java code:

for (int i = 0; i < 3; i++) {          out.write ("\ n");      Out.write ("        <li>");      Out.print (i);      Out.write ("</li>\n");      Out.write ("    ");}

The above code fragment is located in the Servlet's _jspservice method.

That is, any Java code that we write in the JSP script tag will appear as-is in the Servlet's _jspservice method.

Also, because the Java code within the JSP scripting Syntax (<%.%>) tag will appear inside the method, it means that we cannot use keywords such as public, and if I want to declare it, use the declarative syntax.

Because JSP scripts can place any executable statement, you can take advantage of the Java language's capabilities, such as connecting to a database.

4 basic syntax for JSP