o adding exception handling code

git-svn-id: https://svn.apache.org/repos/asf/maven/components/branches/MNG-2766@769609 13f79535-47bb-0310-9956-ffa450edef68

maven-core/src/main/java/org/apache/maven/exception/DefaultExceptionHandler.java

@@ -0,0 +1,73 @@
+package org.apache.maven.exception;
+
+import org.apache.maven.plugin.MojoExecutionException;
+import org.apache.maven.plugin.MojoFailureException;
+import org.codehaus.plexus.component.annotations.Component;
+
+/*
+
+All Possible Errors
+- bad command line parameter
+- malformed settings
+- malformed POM
+- local repository not writable
+- remote repositories not available
+- artifact metadata missing
+- extension metadata missing
+- extension artifact missing
+- artifact metadata retrieval problem
+- version range violation
+- circular dependency
+- artifact missing
+- artifact retrieval exception
+- plugin metadata missing
+- plugin metadata retrieval problem
+- plugin artifact missing
+- plugin artifact retrieval problem
+- plugin dependency metadata missing
+- plugin dependency metadata retrieval problem
+- plugin configuration problem
+- plugin execution failure due to something that is know to possibly go wrong (like compilation failure)
+- plugin execution error due to something that is not expected to go wrong (the compiler executable missing)
+- md5 checksum doesn't match for local artifact, need to redownload this
+
+brett:
+- transitive dependency problems - tracking down
+- invalid lifecycle phase (maybe same as bad CLI param, though you were talking about embedder too)
+- <module> specified is not found
+- POM doesn't exist for a goal that requires one
+- goal not found in a plugin (probably could list the ones that are)
+- parent POM missing (in both the repository + relative path)
+brian:
+- component not found
+- missing goal in plugin
+- removing the scripting options from the core
+
+ */
+
+@Component(role=ExceptionHandler.class)
+public class DefaultExceptionHandler
+    implements ExceptionHandler
+{
+    public ExceptionSummary handleException( Exception exception )
+    {
+        String message;
+        
+        String reference = "http://";
+        
+        if ( exception instanceof MojoFailureException )
+        {
+            message = ((MojoFailureException)exception).getLongMessage();
+        }
+        else if ( exception instanceof MojoExecutionException )
+        {
+            message = ((MojoExecutionException)exception).getLongMessage();
+        }
+        else
+        {
+            message = exception.getMessage();
+        }        
+        
+        return new ExceptionSummary( exception, message, reference );
+    }
+}

maven-core/src/main/java/org/apache/maven/exception/ExceptionHandler.java

@@ -0,0 +1,6 @@
+package org.apache.maven.exception;
+
+public interface ExceptionHandler    
+{
+    ExceptionSummary handleException( Exception e );
+}

maven-core/src/main/java/org/apache/maven/exception/ExceptionSummary.java

@@ -0,0 +1,39 @@
+package org.apache.maven.exception;
+
+// provide a
+// - the exception
+// - useful message
+// - useful reference to a solution, or set of solutions
+// - the configuration gleaned for examination
+// - plugin repositories
+
+public class ExceptionSummary
+{
+    private Exception exception;
+    
+    private String message;
+    
+    private String reference;
+
+    public ExceptionSummary( Exception exception, String message, String reference )
+    {
+        this.exception = exception;
+        this.message = message;
+        this.reference = reference;
+    }
+
+    public Exception getException()
+    {
+        return exception;
+    }
+
+    public String getMessage()
+    {
+        return message;
+    }
+
+    public String getReference()
+    {
+        return reference;
+    }        
+}