ContainerDetector

ContainerDetector utility class

(See attachments for current snapshot versions)

Small utility class for detecting active Servlet Container without access to a ServletContext instance. Mostly meant for use inside logging / diagnostic code. Note there is no container-neutral way to obtain this information, so it has to be done on try-each-known-case basis.

Currently it supports Tomcat and Glassfish.

Note there are no dependencies on javax.servlet.* packages, so it doesn't fail when they're not present.

There is no logging, as one of its intended uses is inside a logging framework, so introducing logging could require unwanted dependencies or circular nasties.

Plans:

• support Jetty
• add some basic System.out logging controlled by a system property
• support other containers

Example code

import net.lilianne_blaze.debugutils.*;
...
// long, all-inclusive string suitable for logging / diagnostics
String s = ContainerDetector.getContainerInfo().toString();
// "tomcat" or "sun-appserver"; likely to remain contant between releases,
// especially useful combined with one of the following props to check for
// versions with known bugs
String type = ContainerDetector.getContainerInfo().getProperties().get(ContainerInfo.SERVLET_CONTAINER_SHORT_NAME);
// works on Glassfish, Tomcat returns null
String buildVersion = ContainerDetector.getContainerInfo().getProperties().get(ContainerInfo.SERVLET_CONTAINER_BUILD);
// works on Tomcat, Glassfish returns null
String buildDate = ContainerDetector.getContainerInfo().getProperties().get(ContainerInfo.SERVLET_CONTAINER_DATE);

Example output

Tomcat 6.0.16

ServletContext.getServerInfo() = Apache Tomcat/6.0.16

ContainerDetector.getContainerInfo() = Apache Tomcat/6.0.16.0 Jan 28 2008 11:35:29

Additional properties:

• servlet.container.date.asString = Jan 28 2008 11:35:29
• servlet.container.longName = Apache Tomcat
• servlet.container.shortName = tomcat
• servlet.container.version.asString = 6.0.16.0

Glassfish

ServletContext.getServerInfo() = Sun Java System Application Server 9.1.1

ContainerDetector.getContainerInfo() = Sun Java System Application Server 9.1.1 (build b38-fcs)

• servlet.container.build.asString = b38-fcs
• servlet.container.longName = Sun Java System Application Server
• servlet.container.shortName = sun-appserver
• servlet.container.version.asString = 9.1.1

Known issues

Too strict SecurityManagers are very likely to prevent detection.

FAQ

Q: What is the project's main goal?

A: To provide a viable alternative to ServletContext.getServerInfo() which can be accessed at any point, from any class and thread.

Q: And why would such a thing be needed?

A: I started this project to be able to access this data from inside a logging framework, which obviously must be able to initialize long before a ServletContext instance is available. Also, typical getServerInfo implementations tend to return only name and major/minor version, while ContainerDetector makes best effort to get full build version and date where available.

Q: Why there's only basic System.out logging?

A: See the above question. It must work reliably when called from inside a Log4J or Logback code. Anything other than System.out would introduce unwanted dependencies and/or nasty circulars.

Q: Why user is able to set server description string ? I can set "I'n not a java server" :D or something :D Furby

A: To make it more test-friendly. In general I don't believe in protecting users from themselves.

Q: Why both NONE_OR_UNKNOWN and UNKNOWN?

A: UNKNOWN means there is a servlet container. NONE_OR_UNKNOWN means servlet classes are available, but without any guarantees whether they are part of a container or a mock objects framework.

Legalese

It is available under Apache Licence 2.0 and WTFPL, with the following exception: if you choose to use any non-final version (i.e. one that is marked as "snapshot", "rc" or "beta") please (i.e. it is a request, not a legal requirement) repack it to another package using JarJar or similar software. See JarJar homepage, JarJar: solves class loading conflicts