Better error messaging when postings_format can be resolved or when a custom postings_format type can't be instantiated.

Relates to #2893

src/main/java/org/elasticsearch/index/codec/CodecModule.java

@@ -25,6 +25,7 @@ import org.elasticsearch.common.inject.AbstractModule;
 import org.elasticsearch.common.inject.Scopes;
 import org.elasticsearch.common.inject.assistedinject.FactoryProvider;
 import org.elasticsearch.common.inject.multibindings.MapBinder;
+import org.elasticsearch.common.settings.NoClassSettingsException;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.index.codec.postingsformat.PostingFormats;
 import org.elasticsearch.index.codec.postingsformat.PostingsFormatProvider;
@@ -92,13 +93,17 @@ public class CodecModule extends AbstractModule {
             String name = entry.getKey();
             Settings settings = entry.getValue();
 
-            Class<? extends PostingsFormatProvider> type =
+            String sType = settings.get("type");
-                    settings.getAsClass("type", null, "org.elasticsearch.index.codec.postingsformat.", "PostingsFormatProvider");
+            if (sType == null || sType.trim().isEmpty()) {
-
-            if (type == null) {
-                // nothing found, see if its in bindings as a binding name
                 throw new ElasticSearchIllegalArgumentException("PostingsFormat Factory [" + name + "] must have a type associated with it");
             }
+
+            Class<? extends PostingsFormatProvider> type;
+            try {
+                type = settings.getAsClass("type", null, "org.elasticsearch.index.codec.postingsformat.", "PostingsFormatProvider");
+            } catch (NoClassSettingsException e) {
+                throw new ElasticSearchIllegalArgumentException("The specified type [" + sType + "] for postingsFormat Factory [" + name + "] can't be found");
+            }
             postingFormatProviders.put(name, type);
         }
 

src/main/java/org/elasticsearch/index/codec/postingsformat/PostingsFormatService.java

@@ -84,7 +84,7 @@ public class PostingsFormatService extends AbstractIndexComponent {
 
     public PostingsFormatProvider get(String name) throws ElasticSearchIllegalArgumentException {
         PostingsFormatProvider provider = providers.get(name);
-        if (name == null) {
+        if (provider == null) {
             throw new ElasticSearchIllegalArgumentException("failed to find postings_format [" + name + "]");
         }
         return provider;

src/main/java/org/elasticsearch/indices/IndexCreationException.java

@@ -19,12 +19,13 @@
 
 package org.elasticsearch.indices;
 
+import org.elasticsearch.ElasticSearchWrapperException;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.IndexException;
 
 /**
  */
-public class IndexCreationException extends IndexException {
+public class IndexCreationException extends IndexException implements ElasticSearchWrapperException {
 
     public IndexCreationException(Index index, Throwable cause) {
         super(index, "failed to create index", cause);