Symptom: you receive random exceptions relating to Kotlin, or other exceptions similar to:

java.lang.RuntimeException: java.lang.NoClassDefFoundError: Could not initialize class

java.lang.RuntimeException: java.lang.NoSuchMethodError: kotlin.jvm.internal.FunctionReferenceImpl.<init>

This may be caused by transitive dependency errors. This FAQ will help you to resolve such errors.

General information

When working with the Java SDK/API, there may be some conflicts with transitive dependencies. To resolve these conflicts, you must first know all the dependencies required by sdk-java, and their versions.

This information is available at https://git.itextsupport.com/projects/DITO/repos/sdk/browse/sdk-java/src/main/resources/NOTICE.txt.

Guarantee

We can only guarantee correct operation of the iText DITO Java SDK/API when using specific versions of transitive dependencies (i.e., the versions that are specified in the NOTICE.txt file). So let's say you have the sdk-java dependency in your project:

<dependency>
    <groupId>com.itextpdf.dito</groupId>
    <artifactId>sdk-java</artifactId>
    <version>${sdk.java.version}</version>
</dependency>

that has the following dependency:

<dependency>
    <groupId>group-a</groupId>
    <artifactId>artifact-a</artifactId>
    <version>${artifact.a.version}</version>
</dependency>

In this case, if your project contains the same dependency but with a different version, then there is a conflict. If Maven has resolved this version conflict in favor of a version that doesn't come from sdk-java, then there is a chance that either some functionality in sdk-java will not work as expected, or some exceptions will be thrown.

Example of resolving conflicts with transitive dependencies

Suppose there is such a case when Maven decided to use a transitive dependency not from sdk-java but from some other dependency. As a concrete example, you can look at the following Spring Boot pom.xml file:

pom.xml 
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.3.9.RELEASE</version>
	</parent>
	<groupId>com.example</groupId>
	<artifactId>demo-1</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo-1</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<repositories>
		<repository>
		<id>dito</id>
		<name>DITO Repository</name>
		<url>https://repo.itextsupport.com/dito</url>
		</repository>
	</repositories>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>com.itextpdf.dito</groupId>
			<artifactId>sdk-java</artifactId>
			<version>2.0.5</version>
		</dependency>
	</dependencies>

</project>

Here you can see that the sdk-java dependency with version 2.0.5 is used:

<dependency>
    <groupId>com.itextpdf.dito</groupId>
    <artifactId>sdk-java</artifactId>
    <version>2.0.5</version>
</dependency>

Note: the problem is reproducible on sdk-java versions 1.4.4 and higher.

When such a pom.xml is used, it may be the case that some methods (e.g. convertTemplateFromPackage in PdfProducer) will throw some exceptions (in the case of convertTemplateFromPackage it would be  java.lang.NoClassDefFoundError:kotlin/KotlinNothingValueException).

To fix this the first thing you should do is to investigate the project dependency tree as well as information about selected versions

mvn dependency:tree -Dverbose=true

and make sure that the versions of project dependencies that are used in sdk-java match the versions in the NOTICE.txt file. In our particular case, the project uses the org.jetbrains.kotlin:kotlin-stdlib:1.3.72 dependency. The version 1.3.72 does not match the version in NOTICE.txt, which in turn leads to the exception described above. So, to fix this, you have several options:

1 The first one is adding the desired transitive dependency version as a direct dependency. You can do this in the following way:

<dependency>
    <groupId>org.jetbrains.kotlin</groupId>
    <artifactId>kotlin-stdlib</artifactId>
    <version>1.4.30</version>
</dependency>

In this case org.jetbrains.kotlin:kotlin-stdlib:1.4.30 will be used according to the tree depth. The resulting pom.xml will look like this:

pom.xml with correct version of org.jetbrains.kotlin:kotlin-stdlib dependency 
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.3.9.RELEASE</version>
	</parent>
	<groupId>com.example</groupId>
	<artifactId>demo-1</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo-1</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<repositories>
		<repository>
		<id>dito</id>
		<name>DITO Repository</name>
		<url>https://repo.itextsupport.com/dito</url>
		</repository>
	</repositories>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.jetbrains.kotlin</groupId>
			<artifactId>kotlin-stdlib</artifactId>
			<version>1.4.30</version>
		</dependency>
		<dependency>
			<groupId>com.itextpdf.dito</groupId>
			<artifactId>sdk-java</artifactId>
			<version>2.0.5</version>
		</dependency>
	</dependencies>

</project>

2 The second one is by using the dependencyManagement section (this section helps Maven to determine the version to select for specified dependencies):

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib</artifactId>
            <version>1.4.30</version>
        </dependency>
    </dependencies>
</dependencyManagement>
pom.xml with dependencyManagement section 
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.3.9.RELEASE</version>
	</parent>
	<groupId>com.example</groupId>
	<artifactId>demo-1</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo-1</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<repositories>
		<repository>
		<id>dito</id>
		<name>DITO Repository</name>
		<url>https://repo.itextsupport.com/dito</url>
		</repository>
	</repositories>

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.jetbrains.kotlin</groupId>
				<artifactId>kotlin-stdlib</artifactId>
				<version>1.4.30</version>
			</dependency>
		</dependencies>
	</dependencyManagement>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>com.itextpdf.dito</groupId>
			<artifactId>sdk-java</artifactId>
			<version>2.0.5</version>
		</dependency>
	</dependencies>

</project>

3 Moreover in some cases you can use the exclusions section to exclude a transitive dependency and avoid any conflict.  avoid any conflicts

Important note: we recommend you explicitly define the following dependencies as they usually cause conflicts:

org.jetbrains.kotlin:kotlin-reflect
org.jetbrains.kotlin:kotlin-stdlib-common
org.jetbrains.kotlin:kotlin-stdlib-jdk7
org.jetbrains.kotlin:kotlin-stdlib-jdk8
org.jetbrains.kotlin:kotlin-stdlib
org.jetbrains.kotlinx:kotlinx-datetime-jvm
org.jetbrains.kotlinx:kotlinx-html-jvm
org.jetbrains.kotlinx:kotlinx-serialization-core-jvm
org.jetbrains.kotlinx:kotlinx-serialization-json-jvm

Important note: when upgrading the sdk-java version, don't forget to check transitive dependencies again to avoid similar issues.