Tomcat to Azure Spring Apps

Migration

Remove the connection to the web server, if present

Disable the connection if Tomcat is connected to a static web server, commonly Apache via mod jk, so that Tomcat operates as a standalone server and generates web redirects from the primary server as required. Think about moving static site content to Azure Storage using the Azure CDN. See Hosting Static Websites in Azure Storage and Quickstart for further details. Connect an Azure Storage account to an Azure CDN account.

Update to Tomcat 9

If the Tomcat version your existing application uses is older than 9, upgrade to Tomcat 9 and ensure it functions properly.

Switch to Maven or Gradle

Maven or Gradle is required by Spring Boot and Spring Cloud for build and dependency management. Before continuing, change to the most recent Maven version if your application uses another build or dependency management system. Although Gradle is also supported, we'll be using Maven for the duration of this session. If you choose to use Gradle, modify the instructions as necessary.

Migrate to Spring Boot

An overview of the code modifications and migrations required to move a Tomcat application to Spring Boot and then to Azure Spring Apps can be found in the table below. If any element from the Legacy column is used in the program, it should be swapped out for its minimum or ideal equivalent from the Minimum or Recommended columns.

1. Include these libraries as dependents in your POM file if your application depends on libraries injected via JNDI resources (such as JDBC drivers). Before removing the libraries from the Tomcat server (usually located in the tomcat/lib directory), ensure the application is functioning properly.

2. Include the parent POM for Spring Boot in your POM file.

3. Your POM file should now include a dependency for the Spring Boot Tomcat starter:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

4. Spring data sources should take the role of Tomcat data sources. Set up Spring DataSources for each database the application uses. Change any code that runs direct SQL queries to utilize JdbcTemplate. For more information on further data access features, such as transaction management and CRUD tooling, go to the Spring Framework and Spring Data documentation.

5. Having servlet implementations inside an embedded servlet container is technically conceivable, but we do not advise it. Instead, use Spring Rest controllers in place of servlet implementations. Replace any non-Spring MVC frameworks that are used in your application with Spring MVC. For further information, refer to the Spring MVC annotated controller reference.

6. Spring beans should be used to recreate all other JNDI requirements. In favor of Spring-idiomatic techniques, use Spring JMS for messaging, for example.

7. Spring Security should take the place of Tomcat Realms. Consider utilizing the Spring Boot Starter for Active Directory with Azure Active Directory to manage authorizations.

8. Reproduce the web.xml-configured Servlet filters using Spring beans or classpath scanning.

9. Static content or JavaScript files should be relocated from the application's source code to src/main/resources if it contains or refers to such content. Update the source code to remove any references to the local file system after relocating the files. To access such files, use the ClassPathResource class from Spring.

Create an Azure Spring Apps instance

Create one if an Azure Spring Apps instance doesn't currently exist in your Azure subscription. Create an application there after that.

Ensure console logging and configure diagnostic settings

Ensure your logging is set up so that all output goes to the console rather than files.

Add a diagnostic setting to an application once it has been published to Azure Spring Apps so that logged events can be used, for instance, through Azure Monitor Log Analytics.

Configure persistent storage

You must set up persistent storage to take the place of the local file system if any portion of your program reads from or writes to the local file system.

Any temporary files should be written to the /tmp directory. You can obtain this directory independently of the OS using System.getProperty ("java.io.tmpdir"). A second option is a java.nio.

Migrate all certificates to KeyVault

You must move certificates to Azure KeyVault and modify the application code to access certificates in KeyVault because Azure Spring Apps does not offer access to the JRE Keystore.

Remove application performance management (APM) integrations

Remove all connections to APM tools and agents. See the Post-migration section for details on setting up performance management using Azure Monitor.

Disable metrics clients, and endpoints in the application

Eliminate any metrics clients in use and any exposed metrics endpoints from your applications.

Deploy the application

Each migrated microservice should be deployed per Quickstart's instructions, excluding the Spring Cloud Config and Registry servers. Your first application should be deployed to Azure Spring Apps.

Post-migration

Once your migration is complete, ensure your application functions as you anticipate. Using the following suggestions, you may then make your application more cloud-native.

• Consider activating Spring Cloud Registry support for your application. By doing this, other deployed Spring apps and clients can dynamically discover your application. To use the Spring Client Load balancer, change any application clients. This enables the client to discover a functioning instance if another instance of the program becomes corrupted or unresponsive by obtaining the addresses of all currently executing instances.
   
• Consider adding a Spring Cloud Gateway instance as an alternative to making your application public. Each application installed in your Azure Spring Apps instance has a single endpoint, thanks to Spring Cloud Gateway. Ensure your freshly deployed application receives traffic from any deployed Spring Cloud Gateways.
   
• To centrally manage and version-control the settings for all of your Spring Cloud applications, take into account adding a Spring Cloud Config Server. First, set up an Azure Spring Apps instance to leverage the newly created Git repository by creating one yourself.
   
• For automatic, dependable deployments, take into account building a deployment pipeline. There are instructions available for Jenkins, GitHub Actions, and Azure Pipelines.
   

• To test code changes in production before making them accessible to some or all of your end-users, think about using staging deployments.
   
• When connecting your application to supported Azure databases, consider adding service bindings. Thanks to these service bindings, you wouldn't have to give your Spring Cloud applications any connection details, such as credentials.
   
• To track the interactions and performance of your applications, think about utilizing Azure Application Insights.
   
• To swiftly identify and respond to abnormal conditions, consider implementing Azure Monitor alert rules and action groups. See Tutorial: Monitor Spring Cloud resources with alerts and action groups for further details.
   
• For reduced latency, increased dependability, and fault tolerance, think about replicating the Azure Spring Apps deployment in a different region. Use Azure Front Door to add SSL offloading and a Web Application Firewall with DDoS protection, or Azure Traffic Manager to load balance installations.
   
• Consider adding an Azure Application Gateway to offer SSL offloading and a Web Application Firewall with DDoS protection if geo-replication is not required.

Frequently Asked Questions

What do you mean by Tomcat on Azure?

The Apache Software Foundation (ASF) created the Java Servlet Container, Tomcat, which is open-source. An extremely well-liked open-source relational database management system is MySQL.

How is Apache Tomcat put to use?

One of Tomcat's connectors receives a request from a client. Tomcat routes this request to the proper Engine for processing. The range of Tomcat's search for the right Engine is constrained because these Engines are included within other elements like hosts and servers.

Can Apache and Tomcat run together?

Running Apache and Tomcat on the same computer is no problem. It's pretty common to run Tomcat on port 8080, run Apache on port 80/443, and use mod_proxy to allow Apache to serve apps hosted by Tomcat.

Can I utilize the Azure App service with Tomcat clustering?

The Azure App Service does not allow Tomcat clustering. Instead of requiring Tomcat-specific capabilities, you can configure and manage scalability and load balancing with Azure App Service. To make the session state accessible across replicas, you can store it in a different place.

How does the Tomcat server work?

A web container called Tomcat manages your servlets and their mappings. Tomcat checks the URL mappings after any request for a servlet is made to apache, and the result is generated in a way browsers can understand.

Conclusion

In this article, we have understood the Tomcat to Azure Spring Apps. We hope this blog will help you understand the concept of Tomcat Azure, and if you want to learn more about Azure, check out our other blogs on the AWS vs azure vs google cloud, Microsoft Azure, Azure Service Fabric, and Microsoft Azure certification.

Refer to our guided paths on Coding Ninjas Studio to learn about Data Structure and Algorithms, Competitive Programming, JavaScript, etc. Enroll in our courses and refer to our mock test available. Have a look at the interview experiences and interview bundle for placement preparations.

Happy Coding!