How comment a JSP expression?

Pure JSP comments look like this:

<%-- Comment --%>

So if you want to retain the "=".you could do something like:

<%--= map.size() --%>

The key thing is that <%= defines the beginning of an expression, in which you can't leave the body empty, but you could do something like this instead if the pure JSP comment doesn't appeal to you:

<% /*= map.size()*/ %>

Code Conventions for the JavaServer Pages Technology Version 1.x Language has details about the different commenting options available to you (but has a complete lack of link targets, so I can't link you directly to the relevant section - boo!)

There are multiple way to comment in a JSP file.

1.  <%-- comment --%>

A JSP comment. Ignored by the JSP engine. Not visible in client machine (Browser source code).

2.  <!-- comment -->

An HTML comment. Ignored by the browser. It is visible in client machine (Browser source code) as a comment.

3. <% my code //my comment %>

Java Single line comment. Ignored by the Compiler. Not visible in client machine (Browser source code).

4.   <% my code /**
         my comment  **/  
       %>

Java Multi line comment. Ignored by the compiler. Not visible in client machine (Browser source code).

But one should use only comment type 1 and 2 because java documentation suggested. these two comment types (1 & 2) are designed for JSP.