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Use SLF4J Parameterized Logging

In this guide we'll look at using OpenRewrite to automatically refactor logging statements to take advantage of performance improvements offered by using slf4j parameterized logging over String concatenation.

Source available recipe module

This guide uses org.openrewrite.recipe:rewrite-logging-frameworks, a Moderne source-available recipe module. Compiled binaries are only available to Moderne customers, hosted at the Code Genome Project. For non-commercial use you can compile and publish the recipe module locally to use the recipes.

Example Configuration​

The ParameterizedLogging recipe has no required configuration options and can be activated directly after taking a dependency on rewrite-logging-frameworks in your build file:

This recipe has no required configuration options. It can be activated by adding a dependency on `org.openrewrite.recipe:rewrite-logging-frameworks` in your build file or by running a shell command (in which case no build changes are needed):

OpenRewrite artifacts, including the Maven and Gradle plugins themselves, are distributed through the Code Genome Project repository (https://artifacts.codegenomeproject.org/maven), which requires authentication. Sign in to the Code Genome Project to create a download token; your build authenticates with the email or username you signed in with, plus that token as the password. See the quickstart guide for details.

  1. Put your Code Genome Project credentials in ~/.gradle/gradle.properties, so that they are not committed alongside your build:
    ~/.gradle/gradle.properties
    codeGenomeUsername=you@example.com
    codeGenomeToken=your-download-token
  2. Add the Code Genome Project repository to your settings.gradle file, so that the plugin itself can be resolved:
    settings.gradle
    pluginManagement {
        repositories {
            maven {
                url = "https://artifacts.codegenomeproject.org/maven"
                credentials {
                    username = providers.gradleProperty("codeGenomeUsername").get()
                    password = providers.gradleProperty("codeGenomeToken").get()
                }
            }
            // Keep the portal for any other plugins your build applies
            gradlePluginPortal()
        }
    }
  3. Add the following to your build.gradle file:
    build.gradle
    plugins {
        id("org.openrewrite.rewrite") version("latest.release")
    }

    rewrite {
        activeRecipe("org.openrewrite.java.logging.slf4j.ParameterizedLogging")
    }

    repositories {
        mavenCentral()
        maven {
            url = "https://artifacts.codegenomeproject.org/maven"
            credentials {
                username = providers.gradleProperty("codeGenomeUsername").get()
                password = providers.gradleProperty("codeGenomeToken").get()
            }
        }
    }

    dependencies {
        rewrite("org.openrewrite.recipe:rewrite-logging-frameworks:3.32.1")
    }
  4. Run gradle rewriteRun to run the recipe.

At this point, you're ready to execute the migration by running mvn rewrite:run or gradlew rewriteRun. After running the migration you can inspect the results with git diff (or equivalent), manually fix anything that wasn't able to be migrated automatically, and commit the results.

For the full list of changes, see the recipe's reference documentation.

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

class Example {
    Logger logger = LoggerFactory.getLogger(Example.class);

    void method(String name, double percent) {
        logger.debug("Process [" + name + "] is at [" + percent * 100 + "%]");
    }

    void asInteger(String numberString) {
        try {
            Integer i = Integer.valueOf(numberString);
        } catch (NumberFormatException ex) {
            logger.warn("some big error: " + ex.getMessage(), ex);
        }
    }
}

See how this recipe works across multiple open-source repositories​

Run this recipe on OSS repos at scale with the Moderne SaaS.

The community edition of the Moderne platform enables you to easily run recipes across thousands of open-source repositories.

Please contact Moderne for more information about safely running the recipes on your own codebase in a private SaaS.