DZone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
Please enter at least three characters to search
Refcards Trend Reports
Events Video Library
Refcards
Trend Reports

Events

View Events Video Library

Zones

Culture and Methodologies Agile Career Development Methodologies Team Management
Data Engineering AI/ML Big Data Data Databases IoT
Software Design and Architecture Cloud Architecture Containers Integration Microservices Performance Security
Coding Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Culture and Methodologies
Agile Career Development Methodologies Team Management
Data Engineering
AI/ML Big Data Data Databases IoT
Software Design and Architecture
Cloud Architecture Containers Integration Microservices Performance Security
Coding
Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance
Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks

Because the DevOps movement has redefined engineering responsibilities, SREs now have to become stewards of observability strategy.

Apache Cassandra combines the benefits of major NoSQL databases to support data management needs not covered by traditional RDBMS vendors.

The software you build is only as secure as the code that powers it. Learn how malicious code creeps into your software supply chain.

Generative AI has transformed nearly every industry. How can you leverage GenAI to improve your productivity and efficiency?

Related

  • How to Introduce a New API Quickly Using Micronaut
  • Building a Real-Time Audio Transcription System With OpenAI’s Realtime API
  • Efficient API Communication With Spring WebClient
  • Implementing API Design First in .NET for Efficient Development, Testing, and CI/CD

Trending

  • GitHub Copilot's New AI Coding Agent Saves Developers Time – And Requires Their Oversight
  • The Future of Java and AI: Coding in 2025
  • Scaling Microservices With Docker and Kubernetes on Production
  • Event Driven Architecture (EDA) - Optimizer or Complicator
  1. DZone
  2. Data Engineering
  3. Databases
  4. How and Why to Serialize Lambdas

How and Why to Serialize Lambdas

Serializing lambdas can be useful in a number of use cases such as persisting configuration, or as a visitor pattern to remote resources.

By 
Peter Lawrey user avatar
Peter Lawrey
·
Jul. 27, 15 · Tutorial
Likes (7)
Comment
Save
Tweet
Share
33.3K Views

Join the DZone community and get the full member experience.

Join For Free

Serializing lambdas can be useful in a number of use cases such as persisting configuration, or as a visitor pattern to remote resources.

Remote Visitors

For example, say I want to access a resource on a remote Map. I can use get/put, but say I just want to return a field from the value of a Map: I can pass a lambda as a visitor to extract the information I want.


MapView userMap = 

     Chassis.acquireMap("users", String.class, UserInfo.class);

userMap.put("userid", new UserInfo("User's Name"));

// print out changes
userInfo.registerSubscriber(System.out::println);



// obtain just the fullName without downloading the whole object

String name= userMap.applyToKey("userid", u -> u.fullName);



// increment a counter atomically and trigger

// an updated event printed with the subscriber.

userMap.asyncUpdateKey("userid", ui -> { 

     ui.usageCounter++; 

     return ui;

});



// increment a counter and return the userid

int count = userMap.syncUpdateKey("userid", 

      ui -> { ui.usageCounter++; return ui;}, 

      ui -> ui.usageCounter);


As you can see, it is easy to add various simple functions, or call a method to perform the action you need.  The only problem is that lambdas by default are not serializable.

Serializable Lambdas

A simple way to make a lambda serializable is to add a cast of & Serializable to a variable referring to an implementation of the lambda.


Function<UserInfo, String> fullNameFunc = (Function<UserInfo,String> & Serializable) ui -> ui.fullName;
String fullName = userInfo.applyToKey("userid", fullNameFunc);


As you can see this introduces a lot of boiler plate.  A key reason to use lambdas is to avoid boiler plate code so what is the alternative?


Making Lambdas Serializable in Your API

Unfortunately the standard APIs cannot be changed or sub-classes to add this but if you have your own API, you can use a Serializable interface.


@FunctionalInterface

public interface SerializableFunction<I, O>extends Function<I, O>, Serializable {

}


This interface can be used as a parameter type.


default <R> R applyToKey(K key, @NotNull SerializableFunction<E, R> function) {
    return function.apply(get(key));
}


The user of your API doesn't have to explicitly say that the lambda is serializable.


// obtain just the fullName without downloading the whole object

String name= userMap.applyToKey("userid", u -> u.fullName);


The remote implementation serializes the lambda, executes it on the server and returns the result.


Similarly, there is methods for applying a lambda to the map as a whole.


Query and Subscription

To support queries, you can't use the built in stream() API if you want to implictly add Serializable. However, you can create one which is as similar as possible.


Map> collect = userMap.entrySet().query()
    .filter(e -> e.getKey().matches("u*d"))
    .map(e -> e.getValue())
    .collect(Collectors.groupingBy(u -> u.usageCounter));


or as a filtered subscription.


// print userid which have a usageCounter > 10 each time it is incremented.        userMap.entrySet().query()
        .filter(e -> e.getValue().usageCounter > 10)
        .map(e -> e.getKey())
        .subscribe(System.out::println);


What makes this different from the regular stream API, is the data could be distributed across many servers and you get a call back when that changes on any server. Only the data you are interested in is sent across the network as the filter and map is being applied on the server.

Java Serialization

Java Serialization is a good generalised, backwardly compatible serialization library. Two of the most common problems that alternatives try to solve is performance and cross platform serialization.


In the example above, fullNameFunc serializes to over 700 bytes and there is very limited options to optimise this to either reduce the size of the message or the amount of garbage it produces.  By comparison, a straight forward binary YAML serialization uses 348, with more options to optimise the serialization.


This raises the problem of how to serialize a lambda using an alternative, or cross platform or faster serialization format.

Alternative Serialization

You can hook into the current serialization mechanism. This is not supported, and it could change at any time but there is not other supported way to do this.


Nevertheless you can do this"


Method writeReplace = lambda.getClass()

                                  .getDeclaredMethod("writeReplace");

writeReplace.setAccessible(true);

SerializedLambda sl = (SerializedLambda) writeReplace.invoke(lambda);


This gives you an object you can inspect to extract the contents of the lambda.  Either to see what method it calls, or to serialize it.  On the deserialization side, you can recreate this object and can readResolve on that object.


Standard API

Currently, there is no standard API for introspection of a lambda.  This is done deliberately so that in future the implementation can be changed, although there is no public JEP to do so.  However, like Unsafe which is internal API, I look forward to the day when we can use a standard API rather than having to dig into the internals of the JVM to implement solutions.


Conclusions

With some changes to your API you can make serializing lambdas largely transparent to the developer.  This makes implementing simple distributed systems easier to use while giving you options to optimise how this is done.


API Serialization

Published at DZone with permission of Peter Lawrey, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Related

  • How to Introduce a New API Quickly Using Micronaut
  • Building a Real-Time Audio Transcription System With OpenAI’s Realtime API
  • Efficient API Communication With Spring WebClient
  • Implementing API Design First in .NET for Efficient Development, Testing, and CI/CD

Partner Resources

×

Comments
Oops! Something Went Wrong

The likes didn't load as expected. Please refresh the page and try again.

ABOUT US

  • About DZone
  • Support and feedback
  • Community research
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • Become a Contributor
  • Core Program
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 3343 Perimeter Hill Drive
  • Suite 100
  • Nashville, TN 37211
  • support@dzone.com

Let's be friends:

Likes
There are no likes...yet! 👀
Be the first to like this post!
It looks like you're not logged in.
Sign in to see who liked this post!