o protecting against null properties in the PPEE

o fixing some composition declarations in embedder component descriptor
o adding notes on classloader mechanism



git-svn-id: https://svn.apache.org/repos/asf/maven/components/trunk@293598 13f79535-47bb-0310-9956-ffa450edef68

maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluator.java

@@ -278,7 +278,7 @@ public class PluginParameterExpressionEvaluator
                 value = project.getProperties().getProperty( expression );
             }
 
-            if ( value == null )
+            if ( value == null && properties != null )
             {
                 // We will attempt to get nab a system property as a way to specify a
                 // parameter to a plugins. My particular case here is allowing the surefire

maven-embedder/pom.xml

@@ -13,7 +13,7 @@
     <plugins>
       <plugin>
         <artifactId>maven-assembly-plugin</artifactId>
-        <version>RELEASE</version>
+        <version>2.0-beta-1</version>
         <configuration>
           <descriptor>src/main/assembly/dep.xml</descriptor>
         </configuration>
@@ -21,6 +21,11 @@
     </plugins>
   </build>
   <dependencies>
+    <dependency>
+      <groupId>plexus</groupId>
+      <artifactId>plexus-utils</artifactId>
+      <version>1.0.4-SNAPSHOT</version>
+    </dependency>  
     <dependency>
       <groupId>org.codehaus.plexus</groupId>
       <artifactId>plexus-container-default</artifactId>
@@ -97,10 +102,6 @@
       <artifactId>maven-core</artifactId>
       <version>2.0-beta-3-SNAPSHOT</version>
     </dependency>    
-    <dependency>
-      <groupId>plexus</groupId>
-      <artifactId>plexus-utils</artifactId>
-    </dependency>
     <dependency>
       <groupId>plexus</groupId>
       <artifactId>plexus-input-handler</artifactId>

maven-embedder/src/main/resources/META-INF/plexus/components.xml

@@ -627,9 +627,11 @@
         <requirement>
           <role>org.apache.maven.extension.ExtensionManager</role>
         </requirement>
+        <!--
         <requirement>
           <role>org.apache.maven.project.injection.ModelDefaultsInjector</role>
         </requirement>
+        -->
         <requirement>
           <role>org.apache.maven.artifact.handler.manager.ArtifactHandlerManager</role>
         </requirement>

maven-embedder/src/test/java/org/apache/maven/embedder/MavenEmbedderTest.java

@@ -70,7 +70,7 @@ public class MavenEmbedderTest
 
         File pomFile = new File( targetDirectory, "pom.xml" );
 
-        MavenProject pom = maven.readProjectWithDependencies( pomFile );        
+        MavenProject pom = maven.readProjectWithDependencies( pomFile );
 
         EventMonitor eventMonitor = new DefaultEventMonitor( new PlexusLoggerAdapter( new MavenEmbedderConsoleLogger() ) );
 
@@ -78,7 +78,7 @@ public class MavenEmbedderTest
                        Collections.singletonList( "package" ),
                        eventMonitor,
                        new ConsoleDownloadMonitor(),
-                       null,
+                       new Properties(),
                        targetDirectory );
 
         File jar = new File( targetDirectory, "target/embedder-test-project-1.0-SNAPSHOT.jar" );

maven-site/src/site/apt/guides/getting-started/classloaders.txt

@@ -0,0 +1,24 @@
+To add a bit of detail for a volunteer to submit as documentation... :)
+
+m2/core/boot is what is in the java classpath (ie, just classworlds,
+which constructs classloaders for the rest of the system)
+
+the top level classloader contains plexus container and plexus utils
+(see m2/core), and also has access to classworlds
+
+the next classloader has the libraries in m2/lib (a bug in beta 1
+incorporated commons-logging and -lang, sorry about that!) In general
+these are just maven libraries. We hope to further separate these in
+future to just be maven apis.
+
+after that, each plugin has its own classloader, including its
+dependencies, itself, and the libraries above. It *does not* contain
+the project dependencies like in m1, but instead has access to a list
+of JAR files in case they are needed.
+
+In addition, a project can list "extensions". These are loaded into
+the same place as m2/lib and so available to the maven core and all
+plugins for the currnet project and subsequent projects (in future, we
+plan to remove it from subsequent projects).
+
+- Brett