PiT 25.0: Fixing Elemental.json Breakage In Vaadin Apps

When upgrading to PiT 25.0, Vaadin developers have encountered an issue where the absence of elemental.json as a transitive dependency breaks their applications. This article delves into the problem, its causes, and provides two potential solutions: either adding the missing third-party dependency or migrating to Jackson. Understanding the root cause and implementing one of these fixes will ensure a smooth transition to PiT 25.0 and maintain the stability of your Vaadin applications. This issue primarily affects projects that rely on functionalities previously provided by the elemental.json library through Vaadin's transitive dependencies. Without it, certain operations related to JSON processing will fail, leading to application errors and unexpected behavior. Let's explore how to address this issue effectively.

Understanding the Issue

The core of the problem lies in the fact that Vaadin no longer automatically includes the elemental.json library as a transitive dependency in PiT 25.0. In previous versions, developers could rely on Vaadin to bring in this library implicitly, allowing them to use its functionalities without explicitly declaring it in their project's dependencies. However, this has changed, and projects now need to either declare the dependency directly or migrate to an alternative library like Jackson. The absence of elemental.json can manifest in various ways, such as compilation errors, runtime exceptions, or unexpected behavior in parts of the application that rely on JSON processing. Therefore, it's crucial to identify whether your project is affected and to take the necessary steps to resolve the issue. Analyzing your project's code and dependencies is the first step in determining whether you need to take action. If you find that your application uses classes or methods from the elemental.json library, you will need to implement one of the solutions discussed below.

Solution 1: Adding the 3rd Party Dependency

The most straightforward solution is to explicitly add elemental.json as a third-party dependency to your project. This involves modifying your project's build configuration file (e.g., pom.xml for Maven or build.gradle for Gradle) to include the necessary dependency declaration. By adding the dependency, you ensure that the elemental.json library is available at compile-time and runtime, resolving the missing dependency issue. This approach is particularly suitable for projects that heavily rely on elemental.json and prefer to continue using it without significant code changes. To add the dependency, you will need to find the correct dependency coordinates for elemental.json from a Maven repository or similar source. Once you have the coordinates, add them to your project's build file, and rebuild the project to download and include the library. Here’s how you can add the dependency using Maven:

<dependency>
    <groupId>com.google.elemental</groupId>
    <artifactId>elemental-json</artifactId>
    <version>PUT_THE_VERSION_HERE</version>
</dependency>

And here’s how to add it using Gradle:

dependencies {
    implementation 'com.google.elemental:elemental-json:PUT_THE_VERSION_HERE'
}

Remember to replace PUT_THE_VERSION_HERE with the actual version number of the elemental-json library. After adding the dependency, ensure that you rebuild your project and test the functionality that relies on elemental.json to verify that the issue is resolved. This approach ensures that your application continues to function as expected with minimal code changes.

Solution 2: Migrating to Jackson

Alternatively, you can migrate your code to use Jackson, a popular and robust JSON processing library. This approach involves replacing all usages of elemental.json with equivalent Jackson functionalities. While this requires more effort and code changes, it can be a worthwhile investment in the long run, as Jackson is widely used and well-supported. Migrating to Jackson can also provide performance benefits and access to a broader range of JSON processing features. This solution is ideal for projects that are willing to invest the time and effort to modernize their codebase and take advantage of the features offered by Jackson. To migrate to Jackson, you will need to add the Jackson dependency to your project and then systematically replace all usages of elemental.json with Jackson equivalents. This may involve changing how you parse JSON, how you create JSON objects, and how you serialize and deserialize data. The specific changes required will depend on how your project currently uses elemental.json. Here’s how you can add the Jackson dependency using Maven:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>PUT_THE_VERSION_HERE</version>
</dependency>

And here’s how to add it using Gradle:

dependencies {
    implementation 'com.fasterxml.jackson.core:jackson-databind:PUT_THE_VERSION_HERE'
}

Again, replace PUT_THE_VERSION_HERE with the actual version number of the jackson-databind library. After adding the dependency, you will need to refactor your code to use Jackson's API for JSON processing. This may involve using classes like ObjectMapper to parse and generate JSON, and using annotations to control how objects are serialized and deserialized. This migration can be a significant undertaking, but it can also result in a more maintainable and performant codebase.

Step-by-Step Migration Guide to Jackson

Migrating from elemental.json to Jackson involves several steps. Here's a detailed guide to help you through the process:

1. Add Jackson Dependency: Include the Jackson library in your project's dependencies. Use the Maven or Gradle snippets provided earlier, ensuring you have the correct version specified.

2. Identify elemental.json Usages: Search your codebase for all instances where elemental.json classes and methods are used. This will give you a clear picture of the scope of the migration.

3. Replace JSON Parsing: Replace elemental.json's JSON parsing with Jackson's ObjectMapper. For example:

   // Old: elemental.json
   import elemental.json.Json;
   import elemental.json.JsonObject;
   JsonObject jsonObject = Json.parse(