How can I solve "org.slf4j.impl.StaticLoggerBinder" error to run my Javalin web app?

Question

I am using IntelliJ IDE where I created a maven project to build a website. I am trying to use Javalin as it is a lightweight framework to use. As per the documentation of Javalin, my pom.xml files is:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>Web-App</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>io.javalin</groupId>
            <artifactId>javalin</artifactId>
            <version>3.13.6</version>
        </dependency>
    </dependencies>

    <properties>
        <maven.compiler.source>15</maven.compiler.source>
        <maven.compiler.target>15</maven.compiler.target>
    </properties>

</project>

And under src/main/java, I created a HelloWorld.java to run my webapp. The code is:

import io.javalin.Javalin;

public class HelloWorld {
    public static void main(String[] args) {
        Javalin app = Javalin.create().start(7000);
        app.get("/", ctx -> ctx.result("Hello World"));
    }
}

When I run, I get a error like this:

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Exception in thread "main" java.lang.NoClassDefFoundError: kotlin/NoWhenBranchMatchedException
    at io.javalin.core.JavalinConfig$Inner.<init>(JavalinConfig.java:73)
    at io.javalin.core.JavalinConfig.<init>(JavalinConfig.java:63)
    at io.javalin.Javalin.<init>(Javalin.java:52)
    at io.javalin.Javalin.create(Javalin.java:88)
    at io.javalin.Javalin.create(Javalin.java:76)
    at HelloWorld.main(HelloWorld.java:5)
Caused by: java.lang.ClassNotFoundException: kotlin.NoWhenBranchMatchedException
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:606)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:168)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
    ... 6 more

Under this circumstances. what could have been my error behind this?

Thanks in advance.

Answer 1

You are missing a logging implementation. I recommend you use this "javalin-bundle" dependency:

<dependency>
    <groupId>io.javalin</groupId>
    <artifactId>javalin-bundle</artifactId>
    <version>3.13.6</version>
</dependency>

It includes some extra libraries, including logging libraries, which are missing if you only use <artifactId>javalin</artifactId>.

(You also get Jackson, which is used by Javalin behind the scenes to handle JSON rsources - for example ctx.json(obj).)

You don't have to use the bundle - you can provide your own logging implementation.