--- a/flys-artifacts/ChangeLog	Tue Sep 18 09:49:45 2012 +0000
+++ b/flys-artifacts/ChangeLog	Tue Sep 18 10:18:30 2012 +0000
@@ -1,3 +1,9 @@
+2012-09-18	Christian Lins	<christian.lins@intevation.de>
+
+	* src/main/java/de/intevation/flys/collections/CollectionDescriptionHelper.java,
+	  src/main/java/de/intevation/flys/collections/FLYSArtifactCollection.java:
+	  Add robustness checks to prevent NPEs (#859).
+
 2012-09-18	Felix Wolfsteller	<felix.wolfsteller@intevation.de>
 
 	Brought showarea-theme setting back (fix issue865).

--- a/flys-artifacts/src/main/java/de/intevation/flys/collections/CollectionDescriptionHelper.java	Tue Sep 18 09:49:45 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/collections/CollectionDescriptionHelper.java	Tue Sep 18 10:18:30 2012 +0000
@@ -6,18 +6,16 @@
 
 import javax.xml.xpath.XPathConstants;
 
+import org.apache.log4j.Logger;
 import org.w3c.dom.Document;
 import org.w3c.dom.Element;
 import org.w3c.dom.Node;
 import org.w3c.dom.NodeList;
 
-import org.apache.log4j.Logger;
-
 import de.intevation.artifacts.ArtifactDatabase;
 import de.intevation.artifacts.ArtifactDatabaseException;
 import de.intevation.artifacts.ArtifactNamespaceContext;
 import de.intevation.artifacts.CallContext;
-
 import de.intevation.artifacts.common.utils.XMLUtils;
 import de.intevation.artifacts.common.utils.XMLUtils.ElementCreator;
 
@@ -63,20 +61,17 @@
         long        ttl,
         CallContext callContext
     ) {
-        this.name     = name;
-        this.uuid     = uuid;
-        this.creation = creation;
-        this.ttl      = ttl;
-        this.context  = callContext;
-        this.database = callContext.getDatabase();
+        this.name      = name;
+        this.uuid      = uuid;
+        this.creation  = creation;
+        this.ttl       = ttl;
+        this.context   = callContext;
+        this.database  = callContext.getDatabase();
+        this.artifacts = new ArrayList<String>();
     }
 
 
     public void addArtifact(String uuid) {
-        if (artifacts == null) {
-            artifacts = new ArrayList<String>();
-        }
-
         if (uuid != null && uuid.length() > 0) {
             artifacts.add(uuid);
         }
@@ -197,10 +192,12 @@
 
 
     protected void appendAttribute(Element root) {
-        Document owner = root.getOwnerDocument();
-        Document attr  = attribute.toXML();
+        if (attribute != null) {
+            Document owner = root.getOwnerDocument();
+            Document attr  = attribute.toXML();
 
-        root.appendChild(owner.importNode(attr.getFirstChild(), true));
+            root.appendChild(owner.importNode(attr.getFirstChild(), true));
+        }
     }
 }
 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :

--- a/flys-artifacts/src/main/java/de/intevation/flys/collections/FLYSArtifactCollection.java	Tue Sep 18 09:49:45 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/collections/FLYSArtifactCollection.java	Tue Sep 18 10:18:30 2012 +0000
@@ -1,5 +1,21 @@
 package de.intevation.flys.collections;
 
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import javax.xml.xpath.XPathConstants;
+
+import org.apache.log4j.Logger;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+
 import de.intevation.artifactdatabase.Backend;
 import de.intevation.artifactdatabase.Backend.PersistentArtifact;
 import de.intevation.artifactdatabase.DefaultArtifactCollection;
@@ -19,22 +35,6 @@
 import de.intevation.flys.exports.OutputHelper;
 import de.intevation.flys.utils.FLYSUtils;
 
-import java.io.IOException;
-import java.io.OutputStream;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-
-import javax.xml.xpath.XPathConstants;
-
-import org.apache.log4j.Logger;
-import org.w3c.dom.Document;
-import org.w3c.dom.Element;
-import org.w3c.dom.Node;
-import org.w3c.dom.NodeList;
-
 /**
  * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
  */
@@ -126,6 +126,11 @@
         CollectionAttribute cAttribute =
             buildOutAttributes(db, context, oldParser, uuids);
 
+        if (cAttribute == null) {
+            log.warn("mergeAttributes: cAttribute == null");
+            return null;
+        }
+
         cAttribute.setLoadedRecommendations(
             getLoadedRecommendations(oldParser.getAttributeDocument()));
 
@@ -450,8 +455,6 @@
         AttributeParser  aParser,
         String[]         uuids)
     {
-        Document doc = XMLUtils.newDocument();
-
         FLYSContext flysContext = FLYSUtils.getFlysContext(context);
         StateEngine engine = (StateEngine) flysContext.get(
             FLYSContext.STATE_ENGINE_KEY);