I
was looking for whether there is any way to make our jsp thread
safe.
I
came across something like You just need to set an attribute to tell
the container whether your jsp is thread safe or not.
<%@
page isThreadSafe="false" %>
By
Default this attribute is true.
If
we use this page attribute in jsp,only one thing changes in the
generated servlet code.
Now
servlet class implements SingleThreadModel Interface.
As
of Java Servlet API 2.4
interface SingleThreadModel
Ensures
that servlets handle only one request at a time. This interface has
no methods.If a servlet implements this interface, you are guaranteed that no two threads will execute concurrently in the servlet's
service method.
The servlet container can make this guarantee by synchronizing access
to a single instance of the servlet, or by maintaining a pool of
servlet instances and dispatching each new request to a free servlet.
Syntax
of isThreadSafe attribute is: <%@ page isThreadSafe="true|false"
%>
If
this attribute is true which is default value,then container may send
multiple concurrent requests simultaneously by starting a thread each
time and if it false,Container will only send one request at a time
and in the order they were received.
Whether
your jsp is thread safe or not,depends totally on the way it was
implemented.
Normally
jsps are thread safe because your run of the JSP does not hold any
member variables.
But
if you use <%! %>,this will place the code at the class level
not in the service method.
Now
this introduction makes jsp unsafe.