Maven + Spring Boot: Found multiple occurrences of org.json.JSONObject on the class path:

Question

When I run mvn test I get this warning. How can I fix it?

Found multiple occurrences of org.json.JSONObject on the class path:

        jar:file:/C:/Users/Chloe/.m2/repository/org/json/json/20140107/json-20140107.jar!/org/json/JSONObject.class
        jar:file:/C:/Users/Chloe/.m2/repository/com/vaadin/external/google/android-json/0.0.20131108.vaadin1/android-json-0.0.20131108.vaadin1.jar!/org/json/JSONObject.class

You may wish to exclude one of them to ensure predictable runtime behavior

Here is my pom.xml. The only reference to JSON is

    <!-- https://mvnrepository.com/artifact/org.json/json -->
    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
    </dependency>

Apache Maven 3.5.3

Answer 1

Add under

 <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>

The following exclusion:

 <scope>test</scope>
    <exclusions>
        <exclusion>
            <groupId>com.vaadin.external.google</groupId>
            <artifactId>android-json</artifactId>
        </exclusion>
    </exclusions>

Similarly, for Gradle projects:

testCompile("org.springframework.boot:spring-boot-starter-test") {
    exclude group: "com.vaadin.external.google", module:"android-json"
}

Answer 2

Background: org.json works great, but has a license clause that some people don't like ("The Software shall be used for Good, not Evil."). So Vaadin wanted to use the library, but couldn't be sure they wouldn't use it for evil someday. Instead, they re-implemented the interface, published android-json and used it as a drop in replacement for org.json. Others began to use android-json as well so that they too would not be bound by the requirement of not using their software for evil.

This is a fine solution, except that when the two libraries are on the classpath, they collide.

Solution: If you get this error from conflicting transitive dependencies, then your best bet is to exclude either Vaadin's android-json library (brought in by Spring), or exclude the org.json library (brought in by another dependency). Vaadin's version is meant to be an identical implementation, but there are subtle differences.

If you're using org.json in your code and it is conflicting with Spring's Vaadin dependency, then I would recommend trying open-json. It's a port of Vaadin's re-implementation of org.json, but they changed the packages so you won't have any conflicts with org.json:json or com.vaadin.external.google:android-json

https://github.com/openjson/openjson

Add gradle dependency:

    implementation('com.github.openjson:openjson:1.0.12')

Or in Maven:

    <dependency>
        <groupId>com.github.openjson</groupId>
        <artifactId>openjson</artifactId>
        <version>1.0.12</version>
    </dependency>

Then update any imports that were being used by org.json classes.