Threadsafe mojos

src/main/java/org/codehaus/mojo/license/AddThirdPartyMojo.java

@@ -67,7 +67,7 @@
  */
 // CHECKSTYLE_ON: LineLength
 @Mojo( name = "add-third-party", requiresDependencyResolution = ResolutionScope.TEST,
-       defaultPhase = LifecyclePhase.GENERATE_RESOURCES )
+       defaultPhase = LifecyclePhase.GENERATE_RESOURCES, threadSafe = true )
 public class AddThirdPartyMojo extends AbstractAddThirdPartyMojo implements MavenProjectDependenciesConfigurator
 {
     private static final Logger LOG = LoggerFactory.getLogger( AddThirdPartyMojo.class );

src/main/java/org/codehaus/mojo/license/AggregatorThirdPartyReportMojo.java

@@ -49,7 +49,8 @@
  * @author Tony Chemit - dev@tchemit.fr
  * @since 1.10
  */
-@Mojo( name = "aggregate-third-party-report", aggregator = true, requiresDependencyResolution = ResolutionScope.TEST )
+@Mojo( name = "aggregate-third-party-report", aggregator = true,
+    requiresDependencyResolution = ResolutionScope.TEST, threadSafe = true )
 public class AggregatorThirdPartyReportMojo
     extends AbstractThirdPartyReportMojo
 {

src/main/java/org/codehaus/mojo/license/CommentStyleListMojo.java

@@ -43,7 +43,7 @@
  * @author tchemit dev@tchemit.fr
  * @since 1.0
  */
-@Mojo( name = "comment-style-list", requiresProject = false, requiresDirectInvocation = true )
+@Mojo( name = "comment-style-list", requiresProject = false, requiresDirectInvocation = true, threadSafe = true )
 public class CommentStyleListMojo
     extends AbstractLicenseMojo
 {

src/main/java/org/codehaus/mojo/license/DownloadLicensesMojo.java

@@ -53,7 +53,7 @@
  * @since 1.0
  */
 @Mojo( name = "download-licenses", requiresDependencyResolution = ResolutionScope.TEST,
-    defaultPhase = LifecyclePhase.PACKAGE )
+    defaultPhase = LifecyclePhase.PACKAGE, threadSafe = true )
 public class DownloadLicensesMojo
     extends AbstractDownloadLicensesMojo
 {

src/main/java/org/codehaus/mojo/license/LicenseListMojo.java

@@ -42,7 +42,7 @@
  * @author tchemit dev@tchemit.fr
  * @since 1.0
  */
-@Mojo( name = "license-list", requiresProject = false, requiresDirectInvocation = true )
+@Mojo( name = "license-list", requiresProject = false, requiresDirectInvocation = true, threadSafe = true )
 public class LicenseListMojo
     extends AbstractLicenseMojo
 {

src/main/java/org/codehaus/mojo/license/LicensesXmlInsertVersionsMojo.java

@@ -52,7 +52,7 @@
  * @since 1.19
  */
 @Mojo( name = "licenses-xml-insert-versions", requiresDependencyResolution = ResolutionScope.TEST,
-    defaultPhase = LifecyclePhase.PACKAGE )
+    defaultPhase = LifecyclePhase.PACKAGE, threadSafe = true )
 public class LicensesXmlInsertVersionsMojo
     extends AbstractLicensesXmlMojo
 {

src/main/java/org/codehaus/mojo/license/ThirdPartyReportMojo.java

@@ -41,7 +41,7 @@
  * @author tchemit dev@tchemit.fr
  * @since 1.1
  */
-@Mojo( name = "third-party-report", requiresDependencyResolution = ResolutionScope.TEST )
+@Mojo( name = "third-party-report", requiresDependencyResolution = ResolutionScope.TEST, threadSafe = true )
 public class ThirdPartyReportMojo extends AbstractThirdPartyReportMojo
 {
 

src/main/java/org/codehaus/mojo/license/UpdateProjectLicenseMojo.java

@@ -43,7 +43,7 @@
  * @author tchemit dev@tchemit.fr
  * @since 1.0
  */
-@Mojo( name = "update-project-license", defaultPhase = LifecyclePhase.GENERATE_RESOURCES )
+@Mojo( name = "update-project-license", defaultPhase = LifecyclePhase.GENERATE_RESOURCES, threadSafe = true )
 public class UpdateProjectLicenseMojo
     extends AbstractLicenseNameMojo
 {

src/main/java/org/codehaus/mojo/license/api/DefaultThirdPartyHelper.java

@@ -44,6 +44,7 @@
 import java.util.SortedMap;
 import java.util.SortedSet;
 import java.util.TreeMap;
+import java.util.concurrent.ConcurrentSkipListMap;
 import org.eclipse.aether.repository.RemoteRepository;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -101,7 +102,12 @@ public class DefaultThirdPartyHelper
     /**
      * Cache of dependencies (as maven project) loaded.
      */
-    private static SortedMap<String, MavenProject> artifactCache;
+    private static final class ArtifactCacheHolder
+    {
+        private ArtifactCacheHolder() {}
+
+        private static final SortedMap<String, MavenProject> artifactCache = new ConcurrentSkipListMap<>();
+    }
 
     /**
      * Constructor of the helper.
@@ -136,11 +142,7 @@ public DefaultThirdPartyHelper( MavenProject project, String encoding, boolean v
      */
     public SortedMap<String, MavenProject> getArtifactCache()
     {
-        if ( artifactCache == null )
-        {
-            artifactCache = new TreeMap<>();
-        }
-        return artifactCache;
+        return ArtifactCacheHolder.artifactCache;
     }
 
     /**

src/main/java/org/codehaus/mojo/license/spdx/SpdxLicenseList.java

@@ -42,23 +42,15 @@
  */
 public class SpdxLicenseList
 {
-    private static volatile SpdxLicenseList latest;
-
-    private static final Object LOCK = new Object();
+    private static final class LatestHolder
+    {
+        private LatestHolder() {}
+        private static final SpdxLicenseList latest = SpdxLicenseListData.createList();
+    }
 
     public static SpdxLicenseList getLatest()
     {
-        if ( latest == null )
-        {
-            synchronized ( LOCK )
-            {
-                if ( latest == null )
-                {
-                    latest = SpdxLicenseListData.createList();
-                }
-            }
-        }
-        return latest;
+        return LatestHolder.latest;
     }
 
     private final String licenseListVersion;