MAPREDUCE-7468: Change add-opens flag's default value from true to false (#6436)

Co-authored-by: Benjamin Teke <bteke@cloudera.com>

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestMapReduceChildJVM.java

@@ -52,7 +52,6 @@ public class TestMapReduceChildJVM {
     MyMRApp app = new MyMRApp(1, 0, true, this.getClass().getName(), true);
     Configuration conf = new Configuration();
     conf.setBoolean(MRConfig.MAPREDUCE_APP_SUBMISSION_CROSS_PLATFORM, true);
-    conf.setBoolean(MRJobConfig.MAPREDUCE_JVM_ADD_OPENS_JAVA_OPT, false);
     Job job = app.submit(conf);
     app.waitForState(job, JobState.SUCCEEDED);
     app.verifyCompleted();

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/MRJobConfig.java

@@ -312,7 +312,7 @@ public interface MRJobConfig {
   public static final String MAPREDUCE_JVM_ADD_OPENS_JAVA_OPT =
     "mapreduce.jvm.add-opens-as-default";
 
-  public static final boolean MAPREDUCE_JVM_ADD_OPENS_JAVA_OPT_DEFAULT = true;
+  public static final boolean MAPREDUCE_JVM_ADD_OPENS_JAVA_OPT_DEFAULT = false;
 
   public static final String IO_SORT_FACTOR = "mapreduce.task.io.sort.factor";
 

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/resources/mapred-default.xml

@@ -1822,12 +1822,12 @@
 
 <property>
   <name>mapreduce.jvm.add-opens-as-default</name>
-  <value>true</value>
+  <value>false</value>
   <description>Since on JDK17 it's no longer possible to use the reflection API to
     access non-public fields and methods add-opens flags should be added to MR AM
     and map/reduce containers regardless of the user specified java opts. Setting
     this to true will add the flags to the container launch commands on nodes with
-    JDK17 or higher. Defaults to true, but the setting has no effect on nodes using
+    JDK17 or higher. Defaults to false, and the setting has no effect on nodes using
     JDK16 and before.
   </description>
 </property>