我已经从JBoss 4升级到了5，根据经验，以下是最重要的注意事项：

• JBoss 5 (and 6 and 7) are not as forgiving as JBoss 4 with XML files. You must make sure that all your deployment descriptor XML files are valid. You may be using DTDs in some files - I recommend upgrading these to use XML schema instead.
• Some libraries may cause incompatibilities. This can be particularly true if you access web services and/or do XML parsing
• If you precompile your JSPs in JBoss 4, you probably won t be able to in JBoss 6/7.
• JBoss 4 and 5 use different message queue implementations. If you have any message queues or topics defined you will need to redefine them.
• JBoss TreeCache is no longer used. If you use this for caching purposes, you will need to change to use the new JBoss cache instead.
• JBoss 5 security is different. If your remote clients require secured access to JBoss, you will need to configure them differently.

一些有用的资源包括：

https://dzone.com/articles/migrating-jboss-4-jboss-5 http://venugopaal.wordpress.com/2009/02/02/jboss405-to-jboss-5ga

JBoss 6官方只针对Java EE Web概要文件进行了认证，因此如果您使用EJB 2.x等“遗留”功能，它们在未来可能不会得到支持。根据应用程序的生命周期，这可能是问题，也可能不是问题。JBoss6目前完全支持EJB2.1，但它还没有通过认证。

我还发现JBoss5处理内存的能力比JBoss4强得多。使用JBoss4，我看到的PermGen错误比使用JBoss5多得多。

我只能从JBoss 5.1.0的生产经验和对版本6的一些调查中说起

JBoss 5是Java EE 5以及JBoss 6和7是Java EE 6。API功能的差异在这些规范中得到了最好的证明。JBoss 6的保质期可能很短；它是仅针对Java EE 6 web配置文件进行了认证，错误修复针对版本7（在撰写本文时为第三个测试版）。

我想你会在JBoss社区论坛上得到更好的答案。

我们从JBoss AS 5升级到JBoss AS7，并着眼于WildFly AS 8.1。现在我们不能迁移到8，因为没有MQ系列JMS 2 RAR。

一些差异：

• The configuration is so much better and simpler. It s no longer spread over 20 XML files in which you configure aspects in XML files. Instead everything is one central place. All ports are configured in one central place, there is no longer an XSL file that transforms server.xml. You can make sense of the configuration file without knowing the implementation details of classes. It s hard to appreciate this if you ve never configured a JBoss 5.x.
• The class loading model looks sane and you get a lot of control through jboss-deployment-structure.xml
• The centralized logging (Slf4j, JUL, JCL, Log4j, …) is really nice.
• The EJB client library looks much more cleaned up. It s down to 10 JARs from 20, half of them are even OSGi bundles (our client is an Eclipse RCP application).
• The EJB client maven dependency mess is gone, instead you now get a BOM POM.
• You get a BOM POM for the server APIs.
• Faster start up and less memory usage. We deploy 80 EJBs and the MQ Series RAR in 6 seconds without much tuning. Our live dataset is somewhere above 200 MB.
• The deployments folder is empty by default
• The (lack of) quality of XNIO is scary. In 7.x it s only used for EJB remoting and we hit several show stopper bugs (deadlocks, double free, socket handle leaks, …). In 8.x it is used for servlets as well instead of Tomcat. There are still a lot of very basic servlet bugs being fixed in undertow.

我们在应用程序中所做的更改：

• change JNDI names to EE 6 standardized names
• migrate from JBoss Cache to Infinispan (part of our code has been migrated to the flat API, some parts still use the tree API)
• security is slightly less flexible (you can no longer fix authenticated and unauthenticated calls)
• some horrible code that relied on details of remote JNDI
• the configuration of the EJB client is different
• all of you scripts for installing, deploying, starting, stopping, …
• ExternalContext is gone, we had to replace it with a different approach
• we replaced MBeans in SARs with @StartUp EJBs
• some ugly hacks for Cocoon

AS7.x系列有很多错误，只有EAP系列才提供修复。如果你想使用7.x而不是8.x，我们强烈建议你购买EAP 6。

这里有一个关于JBoss AS7妥协和未来的有趣线程，还提到了AS5和AS6的问题：

http://community.jboss.org/message/613171

Just wanted to bring this to anyone s attention who might be facing PermGen bloat issue after upgrading to the latest. The JBoss-6 Microcontainer tries to scan for Jboss specific annotations by loading the classes from all the JARs in the class-path on startup. This causes the PermGen bloating as it starts to load all the unwanted classes. To reduce the amount of scanning, the Microcontainer provides another descriptor hook, by means of jboss-scanning.xml. Add this jboss-scanning.xml to the WEB-INF inside WARs and ass jboss-scanning.xml to the META-INF inside EARs.

<scanning xmlns="urn:jboss:scanning:1.0">

    <!-- Purpose: Disable scanning for annotations in contained deployment. -->

</scanning>