Converting your Logger Declarations to Lombok Annotations

Without lombok, loggers are declared in their own field, e.g. private static final Logger log = LoggerFactory.getLogger(FooService.class);. This declaration takes the class it is declared in as a parameter, which a developer might forget to change when copying classes. Other than this parameter the declaration is the same for every class, making it boilerplate code. Lombok can make your code more concise with a class level annotation, e.g. @Slf4

There are different steps to migrate to the lombok annotation depending on the specifics of your project:

Ensuring all Fields have the same name

The loggers generated by Lombok will all have the same name (by default log), so the loggers in your project should have the same name as well. Since the declaration is uniform you can use regular expressions to find outliers. If you have a linux console grep and friends might be sufficient, see Example A^[1].

Example A:Display all logger declarations with type Logger. (There are other types(!), e.g. just Log).

grep -oh "Logger \w* =" -r --include=*.java | awk '{ print $2}' | sort | uniq -c

Ensuring your name matches the generated name

By default, the loggers generated by Lombok will all have the name log. If you are happy to use the default name log, make sure that your logger fields are all called log in their declaration and usages. If you want to keep using a different name you can configure that in your lombok.config. If your fields are all called LOGGER you would need to add lombok.log.fieldName=LOGGER to your lombok.config.

Converting Field declarations into Annotations

Now that the repository has been prepared, we can apply a recipe:

If you are using SLF4J as a logger you can follow the steps below depending on your build system.

For Log4j2, or the loggers from java.util, org.jboss or apache.commons there are recipes as well. You can find them via the sidebar on the left. Lombok supports more logging frameworks like google’s Flogger but there are no recipes for them yet.

Maven POM
Maven Command Line
Gradle
Gradle init script

Add the following to your pom.xml file:

pom.xml

<project>
  <build>
    <plugins>
      <plugin>
        <groupId>org.openrewrite.maven</groupId>
        <artifactId>rewrite-maven-plugin</artifactId>
        <version>5.42.2</version>
        <configuration>
          <activeRecipes>
            <recipe>io.github.timoa.lombok.log.ConvertSlf4j</recipe>
          </activeRecipes>
        </configuration>
        <dependencies>
          <dependency>
            <groupId>io.github.timo-a</groupId>
            <artifactId>rewrite-recipe-starter</artifactId>
            <version>0.4.2</version>
          </dependency>
        </dependencies>
      </plugin>
    </plugins>
  </build>
</project>

Run mvn rewrite:run to run the recipe.

You will need to have Maven installed on your machine before you can run the following command.

Shell

mvn -U org.openrewrite.maven:rewrite-maven-plugin:run -Drewrite.recipeArtifactCoordinates=io.github.timo-a:rewrite-recipe-starter:RELEASE -Drewrite.activeRecipes=io.github.timoa.lombok.log.ConvertSlf4j

Add the following to your build.gradle file:

build.gradle

plugins {
    id("org.openrewrite.rewrite") version("6.25.1")
}

rewrite {
    activeRecipe("io.github.timoa.lombok.log.ConvertSlf4j")
}

repositories {
    mavenCentral()
}

dependencies {
    rewrite("io.github.timo-a:rewrite-recipe-starter:0.4.2")
}

Run gradle rewriteRun to run the recipe.

Create a file named init.gradle in the root of your project.

init.gradle

initscript {
    repositories {
        maven { url "https://plugins.gradle.org/m2" }
    }
    dependencies { classpath("org.openrewrite:plugin:6.25.1") }
}
rootProject {
    plugins.apply(org.openrewrite.gradle.RewritePlugin)
    dependencies {
        rewrite("io.github.timo-a:rewrite-recipe-starter:0.4.2")
    }
    rewrite {
        activeRecipe("io.github.timoa.lombok.log.ConvertSlf4j")
    }
    afterEvaluate {
        if (repositories.isEmpty()) {
            repositories {
                mavenCentral()
            }
        }
    }
}

Run gradle --init-script init.gradle rewriteRun to run the recipe.

1. Explanation: grep shows all sequences of "Logger <fieldname> =", awk prints the word in the middle, sort prepares the data for uniq which displays the counts.