Maven build errors after upgrading from Eclipse Luna to Mars

Question

I've been using Eclipse Luna with the M2E plugin for some time. I recently decided to upgrade to Eclipse Mars but before I did that, I upgraded all my Maven plugins to the latest version. Once I did that, I verified that everything built on the comamnd line and also built inside Eclipse. I then fired up Eclipse Mars, installed the latest M2E plugin, and started importing my project. Unfortunately, things didn't go so well. I'm getting the following errors:

CoreException: Could not get the value for parameter compilerId for plugin execution default-compile: 
PluginResolutionException: Plugin org.apache.maven.plugins:maven-compiler-plugin:3.5 or one of its dependencies could not be resolved: 
The following artifacts could not be resolved: 
 org.apache.maven:maven-plugin-api:jar:3.0, 
 org.apache.maven:maven-model:jar:3.0
 org.sonatype.sisu:sisu-inject-plexus:jar:1.4.2
 org.apache.maven:maven-artifact:jar:3.0
 org.apache.maven:maven-core:jar:3.0
 org.apache.maven:maven-settings:jar:3.0
 org.apache.maven:maven-settings-builder:jar:3.0
 org.apache.maven:maven-repository-metadata:jar:3.0
 org.apache.maven:maven-model-builder:jar:3.0
 org.apache.maven:maven-aether-provider:jar:3.0
 org.sonatype.aether:aether-impl:jar:1.7
 org.sonatype.aether:aether-spi:jar:1.7
 org.sonatype.aether:aether-api:jar:1.7
 org.codehaus.plexus:plexus-classworlds:jar:2.2.3
 org.apache.maven:maven-toolchain:jar:2.2.1: 
 Failure to transfer org.apache.maven:maven-plugin-api:jar:3.0 from https://repo.maven.apache.org/maven2 was cached in the local repository
 resolution will not be reattempted until the update interval of central has elapsed or updates are forced. 
 Original error: Could not transfer artifact org.apache.maven:maven-plugin-api:jar:3.0 from/to central (https://repo.maven.apache.org/maven2): 
 sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to 
 find valid certification path to requested target  pom.xml /pacbridge-utl  line 4  Maven Project Build Lifecycle Mapping Problem

Execution default-resources of goal org.apache.maven.plugins:maven-resources-plugin:2.6:resources failed: 
Plugin org.apache.maven.plugins:maven-resources-plugin:2.6 or one of its dependencies could not be resolved: 
The following artifacts could not be resolved: 
 org.apache.maven:maven-plugin-api:jar:2.0.6
 org.apache.maven:maven-project:jar:2.0.6
 org.apache.maven:maven-profile:jar:2.0.6
 org.apache.maven:maven-artifact-manager:jar:2.0.6
 org.apache.maven:maven-plugin-registry:jar:2.0.6
 org.apache.maven:maven-core:jar:2.0.6
 org.apache.maven:maven-plugin-parameter-documenter:jar:2.0.6
 org.apache.maven:maven-repository-metadata:jar:2.0.6
 org.apache.maven:maven-error-diagnostics:jar:2.0.6
 org.apache.maven:maven-plugin-descriptor:jar:2.0.6
 org.apache.maven:maven-artifact:jar:2.0.6
 org.apache.maven:maven-settings:jar:2.0.6
 org.apache.maven:maven-model:jar:2.0.6
 org.apache.maven:maven-monitor:jar:2.0.6: 
Failure to transfer org.apache.maven:maven-plugin-api:jar:2.0.6 from https://repo.maven.apache.org/maven2 was cached in the local repository, 
resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer 
artifact org.apache.maven:maven-plugin-api:jar:2.0.6 from/to central (https://repo.maven.apache.org/maven2): 
sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: 
unable to find valid certification path to requested target (org.apache.maven.plugins:maven-resources-plugin:2.6:resources:default-resources:process-resources)

I compared my Eclipse settings (between Luna and Mars) and everything looks the same. In particular, I've made sure the Windows/Preferences/General/Network Connections are the same (i.e. my proxies are setup properly) and I've tried running "mvn -U clean install" from the command line. As I say, the command line build runs fine but Eclipse Mars just won't build. Can anyone suggest a solution? BTW: I'm using Maven 3.3.3 with Java 8

Thanks.

Answer 1

It turns out the M2E plugin was using the wrong Settings.xml file, one that did not have a reference to the correct plugin-repo. Once I fixed the that (in Windows->Preferences->Maven->User Settings) thing started working again.