Tag Archives: java

[2021 kcdc] Enterprise Cloud Patterns for Java Devs

Posted on by
Reply

This post is my live blog from KCDC. For more, see the 2021 KCDC live blog TOC

Speaker: Pratik Patel (Azul)

Twitter @prpatel

————————-

Philosophy

  • Monoliths are not elastic. Cloud is
  • Doesn’t waste money
  • Must design for elasticity
  • We learn to avoid premature optimization/keep it simple stupid. In the cloud, we have to do some optimization
  • Need to design for horizontal scaling (adding more servers/virtual servers)
  • Need entire architecture to be elastic. Else have created a bottleneck
  • Think about cosT, adapabiity/agil/security, time to market

Cloud native review

  • Containerized
  • Dynamically orchestrated (actively schedule containers to optimize resource utiilization)
  • Microservices oriented (try to avoid dependencies between microservices – not possible to avoid, but minimize)

Types of Patterns

  • Design and implementation – covered today
  • Performance and scalabity
  • Data management
  • Availability and reliabliliy

Ambassador Pattern

  • For transitioning legacy apps – could be monolith or SOAP or Java EE or Spring Boot or whatever to microservices
  • The Ambassador is a proxy. It adds monitoring, retry and a protocol adapter (hide SOAP/RMI from clients) and delegates to the legacy app.
  • This lets the callers all the Ambassador and get these cloud capabilities.
  • Implemented as a sidecar (does extra stuff)
  • Use Spring RestTemplate (now called WebClient) or Microprofile Rest client 2.0
  • For end user/callers

Anti-corruption pattern

  • Also for transitioning legacy apps
  • Callers is another service (microservice, cloud function, event driven api)
  • Does more than ambassador.
  • Facade/adapter pattern
  • Firewalls legacy apps
  • Useful for migrating large glegacy app
  • Protocol adapers
  • Legacy unchangeable APIs
  • Compartmentalize legacy app to protect requests coming in and rest of system in case something gos wrong
  • Spring Reg Template or Microprofile Rest client 2.0
  • Must define specific endpoints

Gateway aggregation pattern

  • For when app needs to call multiple services (ex: auth, media)
  • Calls multiple services and returns the results of multiple services to caller in one shot
  • Groups related services into one API call
  • Avoids death star anti-pattern when everything cals everything else
  • Client calls gateway not services directly
  • MUst think about how to handle failures in downstream services
  • Use SprIng AsyncRestTemplate (or web client) or GraphQL (Sprin, Microproile or SmallRye) – note that graphql introduces dependencies. Good to return a bunch of related data.

Back end for front end (BFF)

  • For flexibiity and performance
  • Adapter by client type (ex: mobile, web mobile, web desktop)
  • Returns data in way most practical and efficient for that client
  • Calls microservice and/or legacy app
  • Can be an implementation of a gateway aggregation pattern
  • Make sure not premature optimzation
  • Data can be shaped and size for specific needs
  • Improved performance
  • Could introduce code duplication
  • Are front and back end devs on same team.
  • Sprint AsyncRet Tmplate or Microprofile CompetableFuture or RestClientBuilder
  • Can be different URLs by service type – ex: mobile url (or header sniffing in API gateway)

Gateway Routing

  • Commonly used/misused
  • Calls proper service based on URL
  • Helps minimize change to clients
  • Reducing coupling directly to services
  • Tradeoffs: latency, bottleneck
  • Spring RestController or Microprofile JAXRS. Or cloud pattforms APAI gateway

URLs

https://docs.microsoft.com/en-us/azure/architecture/patterns/

https://aws.amazon.com/architecture/

My take

This was very fast moving, but I found it understandable. I learned a lot. I liked Pratik’s hand drawings of the patterns. It was also interesting that most people were using AWS at a primarily .NET conference

why java records aren’t quite immutable

Posted on by
8

A new type called a “record” was previewed in Java 14 and released in Java 16. One of the benefits is that it creates immutable objects. Kind of.

An immutable record

This is record is an immutable object. Since it is a record, it is automatically final and has no setters. All is good.

public record Book (String title, int numPages) { }

A mutable record

There there is this record. Do you see why it is mutable?

public record Book (String title, int numPages, List<String> chapters) { }

The problem is that records use shallow immutability. The caller can’t change the “chapters” object to a different reference. The caller can change the values in the “chapters” to their heart’s content. That means this object is still mutable.

Here’s an example showing that the code prints [1, 2, 3] and therefore changes the list of chapters.

List<String> chapters = new ArrayList<>();
chapters.add("1");

Book book = new Book("Breaking and entering", 289, chapters);

chapters.add("2");
book.chapters().add("3");
System.out.println(book.chapters());

Making the record actually be immutable

It’s pretty easy to make the Book record actually be immutable. In fact, it only requires three extra lines! Records have a compact constructor which takes care of the setting fields for you. However, you can choose to change that behavior. In this example, I rely on the default set of “title” and “numPages”. However, for “chapters”, I choose to make an immutable copy to prevent changing the list.

public record Book (String title, int numPages, List<String> chapters) {

    public Book {
        chapters = List.copyOf(chapters);
    }
}

Now the test program fails with an UnsupportedOperationException. Much better. A real immutable record.

Happy Book Birthday! OCP Java 11 Practice Tests Now Shipping!

Posted on by
Reply

Jeanne and I are ecstatic to announce our new book, OCP Java 11 Practice Tests, is now shipping! It’s the first book in print custom written for the new 1Z0-819 Java 11 Certification Exam as well as the 1Z0-817 Java 11 Upgrade Exam.

Want to become Java 11 Certified but not sure where to start? Purchase our new Java 11 Practice Tests book along with our Java 11 Complete Study Guide, now available as The Java 11 Complete Certification Kit. While Oracle restructured the 1Z0-815 and 1Z0-816 Exams into the 1Z0-819 Exam, the material is almost identical (see this post for more details), making the Java 11 Complete Study Guide along with our new Java 11 Practice Tests Book the best source of material for learning everything you need to become a Java 11 Certified Professional!

Like our previous books, we will post any updates or notes on this blog’s Java 11 Practice Tests Book page.

A special thanks to all of our friends and family that helped write this book in the midst of the global pandemic. It’s been a challenging year and we couldn’t have done it without your support!