HBASE-5861 ADDENDUM (missed new MapredcueTestingShim.java file)

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1330078 13f79535-47bb-0310-9956-ffa450edef68

src/test/java/org/apache/hadoop/hbase/mapreduce/MapreduceTestingShim.java

@@ -0,0 +1,88 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.hadoop.hbase.mapreduce;
+
+import java.io.IOException;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.mapreduce.Job;
+import org.apache.hadoop.mapreduce.JobContext;
+import org.apache.hadoop.mapreduce.JobID;
+
+/**
+ * This class provides shims for HBase to interact with the Hadoop 1.0.x and the
+ * Hadoop 0.23.x series.
+ * 
+ * NOTE: No testing done against 0.22.x, or 0.21.x.
+ */
+abstract public class MapreduceTestingShim {
+  private static MapreduceTestingShim instance;
+
+  static {
+    try {
+      // This class exists in hadoop 0.22+ but not in Hadoop 20.x/1.x
+      Class c = Class
+          .forName("org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl");
+      instance = new MapreduceV2Shim();
+    } catch (Exception e) {
+      instance = new MapreduceV1Shim();
+    }
+  }
+
+  abstract public JobContext newJobContext(Configuration jobConf)
+      throws IOException;
+
+  public static JobContext createJobContext(Configuration jobConf)
+      throws IOException {
+    return instance.newJobContext(jobConf);
+  }
+
+  private static class MapreduceV1Shim extends MapreduceTestingShim {
+    public JobContext newJobContext(Configuration jobConf) throws IOException {
+      // Implementing:
+      // return new JobContext(jobConf, new JobID());
+      JobID jobId = new JobID();
+      Constructor<JobContext> c;
+      try {
+        c = JobContext.class.getConstructor(Configuration.class, JobID.class);
+        return c.newInstance(jobConf, jobId);
+      } catch (Exception e) {
+        throw new IllegalStateException(
+            "Failed to instantiate new JobContext(jobConf, new JobID())", e);
+      }
+    }
+  };
+
+  private static class MapreduceV2Shim extends MapreduceTestingShim {
+    public JobContext newJobContext(Configuration jobConf) {
+      // Implementing:
+      // return Job.getInstance(jobConf);
+      try {
+        Method m = Job.class.getMethod("getInstance", Configuration.class);
+        return (JobContext) m.invoke(null, jobConf); // static method, then arg
+      } catch (Exception e) {
+        e.printStackTrace();
+        throw new IllegalStateException(
+            "Failed to return from Job.getInstance(jobConf)");
+      }
+    }
+  };
+
+}