Here is a small checklist about how to migrate a legacy migration and to ensure its success.
This article is part of my work to explain my knowledge about Software migration in the company Byoskill.
This article is part of my working notes on the subject of "How to migrate Web applications running on JBoss AS 5 to the version 7".
I will go straight to the details though here is some lines about JBoss Server.
From Wikipedia : JBoss Application Server(Now called Wildfly) is an application server authored by JBoss, now developed by Red Hat. WildFly is written in Java, and implements the Java Platform, Enterprise Edition (Java EE) specification. It runs on multiple platforms.
On 20 November 2014, JBoss Application Server was renamed Wildfly.
The product history according Wikipedia is :
The JBoss AS community project has been renamed to the WildFly community project wildfly.org
According this JBoss 5 to 7 in 11 steps, the benefits are :
Processing time decreased by 25% without any code change. Development speed increased in my opinion (it is really hard to measure it) by 50% and we are much more productive (faster server restarts). Memory footprint lowered from 1GB to 512MB. Finally automatic application redeployment finally works! However there is always a price to pay – the migration took us 4 weeks (2 sprints).
Thanks to the presentation from Roberto Cortez, we have a clear picture of the migration.
JBOSS 5 Architecture
JBOSS 7 Architecture
When the PAAS or the Web application server have to be upgraded, several regressions may happen. The team has to pay attention to :
Server functionalities and integration : between the versions, some functionalities and integrations provided by the server may have evolved, be fixed or simply disappeared.
Server configuration : The way the server has been configured, using scripts, GUI, may have changed, forcing the team to change their configuration files and finding the corresponding new way of doing it.
Server deployment configuration : Your deployment model configuration may have to be upgraded : single node, clustered mode, disaster recovery, high availability, reverse-proxying may behave differently in the new versions.
Application deployment configuration : the way to deploy your web applications may have changed in the new versions (GUI mode to script mode…)
Server API Regressions : usually Web Application servers are implementing a specific JEE API version, Servlet API and so on. These API may have changed causing regressions in your applications.
Application regressions : JBoss is including many components extending the JEE with BPM, Persistence, implementation. It is really important to track your dependencies (using Tattletale or mvn dependencies:tree) and interview your team about possible hacks and fixes to overcome the limits of JEE 5. This kind of workaround is difficult to migrate.
Training and risk management : This kind of migration contains its part of risks and changes. Both can create frictions inside your team of between the IT Team and your Dev teams. To ease the migration, don’t forget to dedicate some time to your teams into training to learn the new features of JAS 7. You will also have to adapt your project management to freeze for a while the features until the migration has been done.
This section is providing a checklist to help developers and managers to evaluate the migration risk of their applications.
Here is a list of common issues during the migration of applications with JBOSS AS.
4.2. Debug Migration Issues 4.2.1. Debug and Resolve Migration Issues 4.2.2. Debug and Resolve ClassNotFoundExceptions and NoClassDefFoundErrors 4.2.3. Find the JBoss Module Dependency 4.2.4. Find the JAR in the Previous Install 4.2.5. Debug and Resolve ClassCastExceptions 4.2.6. Debug and Resolve DuplicateServiceExceptions 4.2.7. Debug and Resolve JBoss Seam Debug Page Errors
There is a deadlock when using EJB remoting over SSL. This deadlock is present even in EAP 6.2. We’re now at the point when we have quite a patch set of features backported from WildFly to AS 7.
JMS : JBoss Messaging server has been deprecated and the compatibility with a JBOSS AS 5 server is really tough to maintain. Some solutions exists as explained below in the article.
Here is a summary of the evolutions between the JBoss AS version 5 and the version 6.
Here is the compiled list of modifications including the minor version fixes.
In JBoss Enterprise Application Platform 5, the class loading architecture was hierarchical. In JBoss Enterprise Application Platform 6, class loading is based on JBoss Modules. This offers true application isolation, hides server implementation classes, and only loads the classes your application needs. Class loading is concurrent for better performance. Applications written for JBoss Enterprise Application Platform 5 must be modified to specify module dependencies and in some cases, repackage archives.
[Server functionality, Server deployment configuration] Domain Management : In JBoss Enterprise Application Platform 6, the server can be run as a standalone server or in a managed domain.
[Application Deployment] Deployment Configuration : Standalone Servers and Managed Domains : Boss Enterprise Application Platform 5 used profile based deployment configuration. These profiles were located in the EAP_HOME/server/ directory. Applications often contained multiple configuration files for security, database, resource adapter, and other configurations. In JBoss Enterprise Application Platform 6, deployment configuration is done using one file. JBoss Enterprise Application Platform 5 configuration files must be migrated to the new single configuration file.
[Server functionality, Application deployment configuration] Ordering of deployments : Application Platform 5 applications that consist of multiple modules deployed as EARs and use legacy JNDI lookups instead of CDI injection or resource-ref entries may require configuration changes.
[Server functionality, Application deployment configuration] Directory Structure and Scripts : As previously mentioned, JBoss Enterprise Application Platform 6 no longer uses profile based deployment configuration, so there is no EAP_HOME/server/ directory.
[Server application, Application deployment configuration, Application regression JNDI Lookups JBoss Enterprise Application Platform 6 now uses standardized portable JNDI namespaces.
[Server functionality, Server configuration, Application configuration, Application code] : Changing logging dependencies
[Server API, Application configuration regressions] Resource adapter configuration : In previous versions of the application server, the resource adapter configuration was defined in a file with a suffix of *-ds.xml. In JBoss Enterprise Application Platform 6, a resource adapter is configured in the server configuration file.
[Server libraries] Technologies upgrade : JDK 6, JSF 2, Bean Validation (JSR-303), CDI, EJB 3 (1.1.13)
VFS Library update
[Server functionalities] new server functionalities : Mod_cluster, JBoss Embedded AS
[Application deployment] The legacy pooled invoker has been removed. Applications using the pooled invoker should switch to the JBoss Remoting-based unified invoker, which has been the default detached invoker since 4.2.
Here is the compiled list of modifications including the minor version fixes.
Unlike previous releases, with AS 7.1, remote access requires secure authentication by default. This includes both managment (native, jmx, etc) and various remote application protocols (ejb, jndi, jms, etc); Added SSL support for the Remoting interfaces.
[Application configuration deployment] Management API improvements : All configuration attributes are updatable via the CLI. Direct edits to the XML are not necessary.
[Server functionality] Various Administration Console Improvements and Management changes
[Server API] Remote Connectivity Added support for remote EJB, JNDI and JMX invocation over JBoss Remoting 3, IIOP, Remote JMS. Three modes for accessing remote EE components using JNDI (Client, Traditional Remote, and Delegated).
[Server deployment model] Clustering Enhancements : Standalone Servers and Managed Domains : Numerours fixes in HTTP Session Replication, Clustered Web SSO, EJB Stateful Session Bean Replication, EJB load-balancing and failove, JPA XPC propagation
[Server functionality] CLI Regressions jboss-admin.sh renamed to jboss-cli.sh, data-source add" "--pool-name" argument seems to have changed to "–name".
[Server libraries] Technologies upgrade :
Upgrade Google Guava to 11.0.2
[Server functionalities] new server functionalities : Mod_cluster, JBoss Embedded AS
[Application deployment] The legacy pooled invoker has been removed. Applications using the pooled invoker should switch to the JBoss Remoting-based unified invoker, which has been the default detached invoker since 4.2.
[Server functionalities] new server functionalities : Mod_cluster, JBoss Embedded AS
[Application deployment] The legacy pooled invoker has been removed. Applications using the pooled invoker should switch to the JBoss Remoting-based unified invoker, which has been the default detached invoker since 4.2.
According link, we thought it would be really hard to connect with JMS server based on JBoss 5. It turned out that you have 2 options and both work fine:
Repackaging Dependencies and fix the EAR Layout: link
Install and configure the JDBC Driver link
Update the Resource Adapter Configuration
Configure the datasource for Hibernate and JPA : If your application uses JPA and currently bundles the Hibernate JARs, you may want to use the Hibernate that is included with JBoss Enterprise Application Platform 6.
In WildFly 8, a resource adapter is configured in the server configuration file. If you are running in domain mode, the configuration file is the domain/configuration/domain.xml file. If you are running in standalone mode, you will configure the resource adapter in the standalone/configuration/standalone.xml file.
More details there How to migrate from AS5 or AS6 to Wildfly
Here is the list of tasks implying some rewriting inside your application code.
Migration JEE 5 to JEE 6
Upgrade to JPA 2.0
Update your SOAP Implementations using JBossWS-CXF
Upgrade Hibernate from 3 to 4
Replacing JBOSS Cache by Infinispan Cache
Configure JAX-RS / Resteasy changes
Fix Hibernate’s sequencer
Replace JBOSS AOP Interceptors : JBoss AOP was used by the EJB container. However, in AS 7, the EJB container uses a new mechanism. If your application uses JBoss AOP, you need modify your application code as follows.
Migrating JNDI : Migrating JNDI namespaces
Update the datasources : link
Rewriting of your RMI Code : oss 5 and 7 are totally different and this kind of communication will not work.
Using CDI instead of plain old Singletons
Here is a list of useful tools to assist you in your migration.
IronJacamar : to update your datasource configuration
Tattletale : to find the application dependencies
Gilder : An application for migrating the configuration of JBoss AS 5-based servers to JBoss AS 7-based servers.
Tools and tooling to migrate to JBOSSS 6 : Link
Upgrades to newer versions of WildFly or JBoss EAP may be handled using the JBoss Windup migration tool. JBoss Windup migration tool
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