Fix issue malformed solr documents when on field receives two updates

An issue occurred, when a field received two different modifications
(e.g. add and remove). The malformed solr document added a new field,
for each update.

Author: eberhardtj

src/main/java/org/metafacture/contrib/solr/SolrDocumentBuilder.java

@@ -16,6 +16,7 @@
 package org.metafacture.contrib.solr;
 
 import org.apache.solr.common.SolrInputDocument;
+import org.apache.solr.common.SolrInputField;
 import org.metafacture.contrib.framework.SolrDocumentReceiver;
 import org.metafacture.framework.FluxCommand;
 import org.metafacture.framework.MetafactureException;
@@ -79,11 +80,24 @@ public void startEntity(String name) {
     }
 
     @Override
+    @SuppressWarnings("unchecked")
     public void endEntity() {
         if (!updateMethod.isEmpty()) {
-            Map<String,Object> atomicUpdateAction = new HashMap<>();
-            atomicUpdateAction.put(updateMethod, new ArrayList<>(updateFieldValues));
-            document.addField(updateFieldName, atomicUpdateAction);
+
+            SolrInputField field = document.getField(updateFieldName);
+            if (field == null) {
+                // New field
+                Map<String,Object> atomicUpdateAction = new HashMap<>();
+                atomicUpdateAction.put(updateMethod, new ArrayList<>(updateFieldValues));
+                document.addField(updateFieldName, atomicUpdateAction);
+            } else {
+                // Modify field
+                Object o = field.getValue();
+                if (o instanceof Map) {
+                    Map<String,Object> atomicUpdateAction = (Map<String,Object>) o;
+                    atomicUpdateAction.put(updateMethod, new ArrayList<>(updateFieldValues));
+                }
+            }
         }
         updateMethod = "";
         updateFieldValues = new ArrayList<>();

src/test/java/org/metafacture/contrib/solr/SolrDocumentBuilderTest.java

@@ -147,4 +147,24 @@ public void shouldContainTwoAtomicUpdates() {
         assertThat(valueMap2.keySet(), hasItem("set"));
         assertThat(valueMap2.get("set"), hasItem("New Title"));
     }
+
+    @Test
+    @SuppressWarnings("unchecked")
+    public void shouldContainTwoAtomicUpdatesForOneField() {
+        builder.startRecord("id1");
+        builder.startEntity("add");
+        builder.literal("name", "alice");
+        builder.literal("name", "bob");
+        builder.endEntity();
+        builder.startEntity("remove");
+        builder.literal("name", "claire");
+        builder.endEntity();
+        builder.endRecord();
+        builder.closeStream();
+
+        SolrInputDocument document = buffer.getObject();
+
+        assertThat(document.toString(),
+                is(equalTo("SolrInputDocument(fields: [name={add=[alice, bob], remove=[claire]}])")));
+    }
 }