Simplify ReactorModelPool and use a concurrent map

maven-core/src/main/java/org/apache/maven/project/DefaultProjectBuilder.java

@@ -345,7 +345,7 @@ public class DefaultProjectBuilder implements ProjectBuilder {
         buffer.append("<packaging>").append(artifact.getType()).append("</packaging>");
         buffer.append("</project>");
 
-        return new StringModelSource(buffer, artifact.getId());
+        return new StringModelSource(buffer.toString(), artifact.getId());
     }
 
     @Override
@@ -355,24 +355,15 @@ public class DefaultProjectBuilder implements ProjectBuilder {
 
         List<InterimResult> interimResults = new ArrayList<>();
 
-        ReactorModelPool.Builder poolBuilder = new ReactorModelPool.Builder();
+        ReactorModelPool pool = new ReactorModelPool();
-        final ReactorModelPool modelPool = poolBuilder.build();
 
-        InternalConfig config = new InternalConfig(request, modelPool, modelBuilder.newTransformerContextBuilder());
+        InternalConfig config = new InternalConfig(request, pool, modelBuilder.newTransformerContextBuilder());
 
         Map<File, MavenProject> projectIndex = new HashMap<>(256);
 
         // phase 1: get file Models from the reactor.
         boolean noErrors = build(
-                results,
+                results, interimResults, projectIndex, pomFiles, new LinkedHashSet<>(), true, recursive, config, pool);
-                interimResults,
-                projectIndex,
-                pomFiles,
-                new LinkedHashSet<>(),
-                true,
-                recursive,
-                config,
-                poolBuilder);
 
         ClassLoader oldContextClassLoader = Thread.currentThread().getContextClassLoader();
 
@@ -414,22 +405,14 @@ public class DefaultProjectBuilder implements ProjectBuilder {
             boolean root,
             boolean recursive,
             InternalConfig config,
-            ReactorModelPool.Builder poolBuilder) {
+            ReactorModelPool pool) {
         boolean noErrors = true;
 
         for (File pomFile : pomFiles) {
             aggregatorFiles.add(pomFile);
 
             if (!build(
-                    results,
+                    results, interimResults, projectIndex, pomFile, aggregatorFiles, root, recursive, config, pool)) {
-                    interimResults,
-                    projectIndex,
-                    pomFile,
-                    aggregatorFiles,
-                    root,
-                    recursive,
-                    config,
-                    poolBuilder)) {
                 noErrors = false;
             }
 
@@ -449,7 +432,7 @@ public class DefaultProjectBuilder implements ProjectBuilder {
             boolean isRoot,
             boolean recursive,
             InternalConfig config,
-            ReactorModelPool.Builder poolBuilder) {
+            ReactorModelPool pool) {
         boolean noErrors = true;
 
         MavenProject project = new MavenProject();
@@ -483,7 +466,7 @@ public class DefaultProjectBuilder implements ProjectBuilder {
 
         Model model = request.getFileModel();
 
-        poolBuilder.put(model.getPomFile().toPath(), model);
+        pool.put(model.getPomFile().toPath(), model);
 
         InterimResult interimResult = new InterimResult(pomFile, request, result, listener, isRoot);
         interimResults.add(interimResult);
@@ -563,7 +546,7 @@ public class DefaultProjectBuilder implements ProjectBuilder {
                     false,
                     recursive,
                     config,
-                    poolBuilder)) {
+                    pool)) {
                 noErrors = false;
             }
         }

maven-core/src/main/java/org/apache/maven/project/ReactorModelPool.java

@@ -20,11 +20,11 @@ package org.apache.maven.project;
 
 import java.nio.file.Path;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.maven.model.Model;
 
@@ -34,9 +34,9 @@ import org.apache.maven.model.Model;
  *
  */
 class ReactorModelPool {
-    private final Map<GAKey, Set<Model>> modelsByGa = new HashMap<>();
+    private final Map<GAKey, Set<Model>> modelsByGa = new ConcurrentHashMap<>();
 
-    private final Map<Path, Model> modelsByPath = new HashMap<>();
+    private final Map<Path, Model> modelsByPath = new ConcurrentHashMap<>();
 
     /**
      * Get the model by its GAV or (since 4.0.0) by its GA if there is only one.
@@ -65,19 +65,11 @@ class ReactorModelPool {
         return version;
     }
 
-    static class Builder {
+    void put(Path pomFile, Model model) {
-        private ReactorModelPool pool = new ReactorModelPool();
+        modelsByPath.put(pomFile, model);
-
+        modelsByGa
-        Builder put(Path pomFile, Model model) {
+                .computeIfAbsent(new GAKey(getGroupId(model), model.getArtifactId()), k -> new HashSet<>())
-            pool.modelsByPath.put(pomFile, model);
-            pool.modelsByGa
-                    .computeIfAbsent(new GAKey(getGroupId(model), model.getArtifactId()), k -> new HashSet<Model>())
                 .add(model);
-            return this;
-        }
-
-        ReactorModelPool build() {
-            return pool;
     }
 
     private static String getGroupId(Model model) {
@@ -87,7 +79,6 @@ class ReactorModelPool {
         }
         return groupId;
     }
-    }
 
     private static final class GAKey {
 
@@ -109,9 +100,10 @@ class ReactorModelPool {
             if (this == obj) {
                 return true;
             }
-
+            if (!(obj instanceof GAKey)) {
+                return false;
+            }
             GAKey that = (GAKey) obj;
-
             return artifactId.equals(that.artifactId) && groupId.equals(that.groupId);
         }
 
@@ -122,9 +114,7 @@ class ReactorModelPool {
 
         @Override
         public String toString() {
-            StringBuilder buffer = new StringBuilder(128);
+            return groupId + ':' + artifactId;
-            buffer.append(groupId).append(':').append(artifactId);
-            return buffer.toString();
         }
     }
 }