Fix Cascading Local Mode NoClassDefFoundError when es.input.json=true (#937)

When using Cascading local mode any attempt to load JSON data with es.input.json=true fails with a NoClassDefFoundError attempting to load non-existent Hadoop classes.

Author: cwensel

mr/src/main/java/org/elasticsearch/hadoop/mr/SafeWritableConverter.java

@@ -0,0 +1,45 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.hadoop.mr;
+
+import org.apache.hadoop.io.BytesWritable;
+import org.apache.hadoop.io.Text;
+import org.elasticsearch.hadoop.util.BytesArray;
+
+/**
+ *
+ */
+class SafeWritableConverter {
+    public SafeWritableConverter() {
+        Text.class.getName(); // force class to be loaded
+    }
+
+    public void invoke(Object from, BytesArray to) {
+        // handle common cases
+        if (from instanceof Text) {
+            Text t = (Text) from;
+            to.bytes(t.getBytes(), t.getLength());
+        }
+        if (from instanceof BytesWritable) {
+            BytesWritable b = (BytesWritable) from;
+            to.bytes(b.getBytes(), b.getLength());
+        }
+    }
+}

mr/src/main/java/org/elasticsearch/hadoop/mr/WritableBytesConverter.java

@@ -18,26 +18,26 @@
  */
 package org.elasticsearch.hadoop.mr;
 
-import org.apache.hadoop.io.BytesWritable;
-import org.apache.hadoop.io.Text;
 import org.elasticsearch.hadoop.serialization.JdkBytesConverter;
 import org.elasticsearch.hadoop.util.BytesArray;
 
 public class WritableBytesConverter extends JdkBytesConverter {
 
+    private static SafeWritableConverter safeWritableConverter;
+
+    static {
+        try {
+            safeWritableConverter = new SafeWritableConverter();
+        } catch (Error e) {
+            // no Hadoop libs loaded
+        }
+    }
+
     @Override
     public void convert(Object from, BytesArray to) {
-        // handle common cases
-        if (from instanceof Text) {
-            Text t = (Text) from;
-            to.bytes(t.getBytes(), t.getLength());
-            return;
-        }
-        if (from instanceof BytesWritable) {
-            BytesWritable b = (BytesWritable) from;
-            to.bytes(b.getBytes(), b.getLength());
-            return;
-        }
+
+        if (safeWritableConverter != null)
+            safeWritableConverter.invoke(from, to);
 
         super.convert(from, to);
     }