HADOOP-12117. Potential NPE from Configuration#loadProperty with allowNullValueProperties set. (Contributed by zhihai xu)

(cherry picked from commit 99c8c5839b65666e6099116e4d7024e0eb4682b9)

Conflicts:
	hadoop-common-project/hadoop-common/CHANGES.txt
	hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -442,6 +442,9 @@ Release 2.8.0 - UNRELEASED
     HADOOP-12185. NetworkTopology is not efficient adding/getting/removing
     nodes. (Inigo Goiri via cdouglas)
 
+    HADOOP-12117. Potential NPE from Configuration#loadProperty with
+    allowNullValueProperties set. (zhihai xu via vinayakumarb)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java

@@ -2656,14 +2656,14 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
       to.put(entry.getKey(), entry.getValue());
     }
   }
-  
+
   private void loadProperty(Properties properties, String name, String attr,
       String value, boolean finalParameter, String[] source) {
     if (value != null || allowNullValueProperties) {
+      if (value == null) {
+        value = DEFAULT_STRING_CHECK;
+      }
       if (!finalParameters.contains(attr)) {
-        if (value==null && allowNullValueProperties) {
-          value = DEFAULT_STRING_CHECK;
-        }
         properties.setProperty(attr, value);
         if(source != null) {
           updatingResource.put(attr, source);

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java

@@ -1355,6 +1355,19 @@ public class TestConfiguration extends TestCase {
     // it's expected behaviour.
   }
 
+  public void testNullValueProperties() throws Exception {
+    Configuration conf = new Configuration();
+    conf.setAllowNullValueProperties(true);
+    out = new BufferedWriter(new FileWriter(CONFIG));
+    startConfig();
+    appendProperty("attr", "value", true);
+    appendProperty("attr", "", true);
+    endConfig();
+    Path fileResource = new Path(CONFIG);
+    conf.addResource(fileResource);
+    assertEquals("value", conf.get("attr"));
+  }
+
   public static void main(String[] argv) throws Exception {
     junit.textui.TestRunner.main(new String[]{
       TestConfiguration.class.getName()