How to find servlet API version for glassfish server?

Question

While coding a servlet I found a method that says

Since:
    Servlet 3.1

I guess that if I have the autohint from NetBeans to use it is bec

Answer 1

Look at Java EE version. Servlet (and JSP, JSF, EJB, JPA, etc) version goes hand in hand with Java EE version.

• Java EE 8 = Servlet 4.0
• Java EE 7 = Servlet 3.1
• Java EE 6 = Servlet 3.0
• Java EE 5 = Servlet 2.5
• J2EE 1.4 = Servlet 2.4
• J2EE 1.3 = Servlet 2.3
• J2EE 1.2 = Servlet 2.2

Look at the server homepage/documentation how it presents itself. For GlassFish, that is currently (with 4.1):

World's first Java EE 7 Application Server

So, it's Servlet 3.1.

But, with a big but, that's one thing. The second thing is, the webapp's web.xml version also plays a role. Not everyone knows that.

If your webapp's web.xml is declared conform Servlet 3.1 like below,

<?xml version="1.0" encoding="UTF-8"?>
<web-app 
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    version="3.1">

    <!-- Config here. -->
</web-app>

then your webapp will also really run in Servlet 3.1 modus.

However, if it's declared conform Servlet 3.0 like below or even older,

<?xml version="1.0" encoding="UTF-8"?>
<web-app 
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">

    <!-- Config here. -->
</web-app>

then your webapp will run in Servlet 3.0 compatibility modus, even when deployed to a Servlet 3.1 compatible container! The above influences the ServletContext#getMajorVersion() and getMinorVersion(), so they actually say nothing about the container, but only about the webapp itself.

If your webapp's web.xml contains a <!DOCTYPE>, regardless of the DTD and the version, then it will run in Servlet 2.3 compatibility modus, even when there's a newer XSD declared!

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "java.sun.com/dtd/web-app_2_3.dtd">
<web-app 
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    version="3.1">

    <!-- This is WRONG! The DOCTYPE must be removed! -->
</web-app>

Answer 2

First, take a look to Comparing GlassFish Open Source Edition versions 2.x and 3.0.x. Also in your servlet you can add

HttpSession session = request.getSession();
int majorVersion = session.getServletContext().getMajorVersion();
int minorVersion = session.getServletContext().getMinorVersion();