Migrate from EventStore to KurrentDB Java Client

Following the Event Store rebrand to Kurrent, all client libraries have been updated with new package names and improved APIs. This guide shows you how to automatically migrate your Java application from com.eventstore.db-client-java to the new io.kurrent.kurrentdb-client.

Why Migrate?

Latest features and improvements: The KurrentDB client includes performance enhancements and new capabilities
Automated migration: Use OpenRewrite to handle the migration automatically with minimal manual effort

Prerequisites

Java 8 or above
Maven or Gradle build tool
Existing application using com.eventstore.db-client-java dependency

What Gets Updated

This migration will automatically update:

Dependencies: com.eventstore:db-client-java → io.kurrent:kurrentdb-client
Package imports: com.eventstore.dbclient → io.kurrent.dbclient
Class names: EventStoreDBClient → KurrentDBClient
Connection strings: esdb:// → kurrent://
Method names: expectedRevision() → streamRevision()

Step 1: Create Migration Recipe

Create a file named rewrite.yml in the root directory of your Java project:

Click to show rewrite.yml contents

---
type: specs.openrewrite.org/v1beta/recipe
name: io.kurrent.java.UpgradeClient
displayName: Migrate to Kurrent Client
description: >
  Migrate applications to the latest KurrentDB from EventStoreDB client. This recipe will modify an
  application's pom files, migrate to the new names of classes, update package information and change the connection strings.
tags:
  - KurrentDB
  - Kurrent

# Update dependencies
recipeList:
  - org.openrewrite.java.dependencies.ChangeDependency:
      oldGroupId: com.eventstore
      oldArtifactId: db-client-java
      newGroupId: io.kurrent
      newArtifactId: kurrentdb-client
      newVersion: 1.0.2

# Update class names
  - org.openrewrite.java.ChangeType:
      oldFullyQualifiedTypeName: com.eventstore.dbclient.EventStoreDBClientBase
      newFullyQualifiedTypeName: io.kurrent.dbclient.KurrentDBClientBase
  - org.openrewrite.java.ChangeType:
      oldFullyQualifiedTypeName: com.eventstore.dbclient.EventStoreDBClient
      newFullyQualifiedTypeName: io.kurrent.dbclient.KurrentDBClient
  - org.openrewrite.java.ChangeType:
      oldFullyQualifiedTypeName: com.eventstore.dbclient.EventStoreDBClientSettings
      newFullyQualifiedTypeName: io.kurrent.dbclient.KurrentDBClientSettings
  - org.openrewrite.java.ChangeType:
      oldFullyQualifiedTypeName: com.eventstore.dbclient.EventStoreDBConnectionString
      newFullyQualifiedTypeName: io.kurrent.dbclient.KurrentDBConnectionString
  - org.openrewrite.java.ChangeType:
      oldFullyQualifiedTypeName: com.eventstore.dbclient.EventStoreDBProjectionManagementClient
      newFullyQualifiedTypeName: io.kurrent.dbclient.KurrentDBProjectionManagementClient
  - org.openrewrite.java.ChangeType:
      oldFullyQualifiedTypeName: com.eventstore.dbclient.EventStoreDBPersistentSubscriptionsClient
      newFullyQualifiedTypeName: io.kurrent.dbclient.KurrentDBPersistentSubscriptionsClient
  - org.openrewrite.java.ChangeType:
      oldFullyQualifiedTypeName: com.eventstore.dbclient.ExpectedRevision
      newFullyQualifiedTypeName: io.kurrent.dbclient.StreamState

# Update package names
  - org.openrewrite.java.ChangePackage:
      oldPackageName: com.eventstore.dbclient
      newPackageName: io.kurrent.dbclient

# Update method names and connection strings
  - org.openrewrite.text.FindAndReplace:
      find: expectedRevision(
      replace: streamRevision(
      caseSensitive: true
  - org.openrewrite.text.FindAndReplace:
      find: esdb://
      replace: kurrent://
      caseSensitive: true
  - org.openrewrite.text.FindAndReplace:
      find: esdb+discover://
      replace: kurrent+discover://
      caseSensitive: true
---

Step 2: Run the Migration

Choose the command based on your build tool:

Maven

# Run the migration (this will scan and update your code automatically)
./mvnw -U org.openrewrite.maven:rewrite-maven-plugin:run \
  -Drewrite.activeRecipes=io.kurrent.java.UpgradeClient \
  -Drewrite.recipeArtifactCoordinates=org.openrewrite.recipe:rewrite-java-dependencies:1.29.0,org.openrewrite.recipe:rewrite-migrate-java:3.3.0

If you're not using the Maven wrapper, replace ./mvnw with mvn.

Gradle

First, create an init.gradle file with the following contents:

initscript {
    repositories {
        maven { url "https://plugins.gradle.org/m2" }
    }
    dependencies {
        classpath("org.openrewrite:plugin:latest.release")
    }
}

rootProject {
    plugins.apply(org.openrewrite.gradle.RewritePlugin)
    dependencies {
        rewrite("org.openrewrite.recipe:rewrite-java-dependencies:latest.release")
        rewrite("org.openrewrite.recipe:rewrite-migrate-java:latest.release")
    }

    afterEvaluate {
        if (repositories.isEmpty()) {
            repositories {
                mavenCentral()
            }
        }
    }
}

Then run:

# Run the migration
gradle rewriteRun --init-script init.gradle -Drewrite.activeRecipe=io.kurrent.java.UpgradeClient

Step 3: Review Changes

The migration will show output similar to this:

[INFO] Using active recipe(s) [io.kurrent.java.UpgradeClient]
[WARNING] Changes have been made to pom.xml by:
[WARNING]     org.openrewrite.java.dependencies.ChangeDependency: {oldGroupId=com.eventstore, oldArtifactId=db-client-java, newGroupId=io.kurrent, newArtifactId=kurrentdb-client, newVersion=1.0.2}
[WARNING] Changes have been made to LoanApplicationDemo/Java/src/main/java/com/example/CreditController.java by:
[WARNING]     org.openrewrite.java.ChangeType: {oldFullyQualifiedTypeName=com.eventstore.dbclient.EventStoreDBClient, newFullyQualifiedTypeName=io.kurrent.dbclient.KurrentDBClient}
...
[WARNING] Please review and commit the results.
[WARNING] Estimate time saved: 1h 20m

Important: Manual Review Required

ExpectedRevision Changes

The migration automatically converts expectedRevision() calls to streamRevision(), but this assumes you're passing a long parameter. If you're passing a StreamState object, you'll need to manually change these to streamState():

Before:

// This will be auto-converted correctly
appendOptions.expectedRevision(5L);

// This will need manual fixing after migration
appendOptions.expectedRevision(StreamState.NO_STREAM);

After migration:

// Auto-converted (correct)
appendOptions.streamRevision(5L);

// Needs manual fix - change to:
appendOptions.streamState(StreamState.NO_STREAM);

After Migration

Test your application: Run your test suite to ensure everything works correctly.
Fix any StreamState calls: Review compilation errors for streamState() vs streamRevision() usage.
Verify connection strings: Ensure all kurrent:// connections work as expected.
Update documentation: Update any internal docs referencing the old client.
Clean up: Remove the rewrite.yml and init.gradle files if no longer needed.

Need Help?

If you encounter issues during migration:

Check the KurrentDB Java client documentation.
Review the OpenRewrite documentation for advanced configuration.
Open an issue in the KurrentDB Java client repository.

The migration should handle 95% of the changes automatically, saving you significant time while ensuring consistency across your codebase.