why does maven test scoped dependency overriding compile scoped dependency? - maven

Question

I'm trying to figure out why my simple spring boot project no longer works. It is basically straight from spring example with one controller says hello world. I'm using spring-boot-starter-jetty, and spring boot v1.1.10 (tried also 1.2.0). I have some unit test using embedded solr, so solr-core is marked as <scope>test</scope> in the pom. After added the solr-core dependency, the project no longer runs, and it seems the solr-core jetty dependencies are conflicting with spring-boot-starter-jetty dependencies (see screenshot below from Spring Tool Suite).
I thought test scoped dependencies should not interfere with compile scoped dependencies and "is only available for the test compilation and execution phases" - reference?
How do I resolve the conflict? I want to keep spring-boot-starter-jetty when running the spring boot project, and use solr-core when executing tests.
Thanks!
EDIT: adding a sample pom.xml isolated the problem.
<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>test</groupId>
<artifactId>boot-solr-conflict</artifactId>
<version>0.0.1-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.2.0.RELEASE</version>
</parent>
<dependencies>
<!-- tag::jetty[] -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jetty</artifactId>
</dependency>
<!-- end::jetty[] -->
<!-- ################################### -->
<!-- Solr-core dependency for embedded Solr for unit testing. -->
<!-- Causes problem when including this dependency. -->
<dependency>
<groupId>org.apache.solr</groupId>
<artifactId>solr-core</artifactId>
<version>4.7.2</version>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
</exclusion>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
</project>
Application.java
package test;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
#SpringBootApplication
public class Application {
public static void main(String[] args){
SpringApplication.run(Application.class, args);
}
}
MainController.java
package test;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
#Controller
public class MainController {
#RequestMapping("/")
public #ResponseBody String getRoot(){
return "Hello World";
}
}

Answer 1

There are a couple of things going on here.
The mixture of Jetty versions is because Spring Boot only includes dependency management for the Jetty modules that it directly depends upon. You can work around this by declaring your own dependency management for the other Jetty modules that are involved, reusing Boot's jetty.version property. I've opened an issue against Spring Boot so that we can add more complete dependency management for Jetty.
The second part of the problem is that, even once the versions of the Jetty modules have been aligned, Maven omits some of the Jetty compile dependencies as it considers them to be in conflict with the transitive dependencies of solr-core. I don't understand why this is the case as the versions are aligned and the error message confirms as much:
jetty-xml: 8.1.15.v20140411 (omitted for conflict with 8.1.15.v20140411)
You can work around this by using <dependencyManagement> to force some of the dependencies to be compile dependencies by adding <scope>compile</scope>. This was necessary on both jetty-security and jetty-server to get a basic app to start.
Here's the full <dependencyManagement> section that I added to the pom from the question:
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-continuation</artifactId>
<version>${jetty.version}</version>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-deploy</artifactId>
<version>${jetty.version}</version>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-http</artifactId>
<version>${jetty.version}</version>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-io</artifactId>
<version>${jetty.version}</version>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-jmx</artifactId>
<version>${jetty.version}</version>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-security</artifactId>
<version>${jetty.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-server</artifactId>
<version>${jetty.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-servlet</artifactId>
<version>${jetty.version}</version>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-xml</artifactId>
<version>${jetty.version}</version>
</dependency>
</dependencies>
</dependencyManagement>