JAVA-658: Making ReadPreference.primary == ReadPreference.primary() so that it's safe to do equality comparision

Author: jyemin

src/main/com/mongodb/ReadPreference.java

@@ -290,7 +290,7 @@ public static TaggableReadPreference nearest(DBObject firstTagSet, DBObject... r
      * @deprecated As of release 2.9.0, replaced by {@code ReadPreference.primary()}
      */
     @Deprecated
-    public static final ReadPreference PRIMARY = new PrimaryReadPreference();
+    public static final ReadPreference PRIMARY;
 
     /**
      * A secondary-preferred read preference.  Equivalent to calling
@@ -304,7 +304,7 @@ public static TaggableReadPreference nearest(DBObject firstTagSet, DBObject... r
      * @deprecated As of release 2.9.0, replaced by {@code ReadPreference.secondaryPreferred()}
      */
     @Deprecated
-    public static final ReadPreference SECONDARY = new TaggableReadPreference.SecondaryPreferredReadPreference();
+    public static final ReadPreference SECONDARY;
 
     /**
      * @deprecated As of release 2.9.0, replaced by
@@ -324,9 +324,20 @@ public static ReadPreference withTags( final DBObject tags ) {
         return new TaggedReadPreference( tags );
     }
 
-    private static final ReadPreference _PRIMARY = new PrimaryReadPreference();
-    private static final ReadPreference _SECONDARY = new TaggableReadPreference.SecondaryReadPreference();
-    private static final ReadPreference _SECONDARY_PREFERRED = new TaggableReadPreference.SecondaryPreferredReadPreference();
-    private static final ReadPreference _PRIMARY_PREFERRED = new TaggableReadPreference.PrimaryPreferredReadPreference();
-    private static final ReadPreference _NEAREST = new TaggableReadPreference.NearestReadPreference();
+    private static final ReadPreference _PRIMARY;
+    private static final ReadPreference _SECONDARY;
+    private static final ReadPreference _SECONDARY_PREFERRED;
+    private static final ReadPreference _PRIMARY_PREFERRED;
+    private static final ReadPreference _NEAREST;
+
+    static {
+        _PRIMARY = new PrimaryReadPreference();
+        _SECONDARY = new TaggableReadPreference.SecondaryReadPreference();
+        _SECONDARY_PREFERRED = new TaggableReadPreference.SecondaryPreferredReadPreference();
+        _PRIMARY_PREFERRED = new TaggableReadPreference.PrimaryPreferredReadPreference();
+        _NEAREST = new TaggableReadPreference.NearestReadPreference();
+
+         PRIMARY = _PRIMARY;
+         SECONDARY = _SECONDARY_PREFERRED;  // this is not a bug.  See SECONDARY Javadoc.
+    }
 }

src/main/com/mongodb/util/MyAsserts.java

@@ -88,6 +88,11 @@ public static void assertEquals( String a , Object b ){
 	_assertEquals( a , b == null ? null : b.toString() );
     }
 
+    public static void assertSame(Object a, Object b) {
+        if ( a != b )
+            throw new MyAssert( a + " != " + b );
+    }
+
     public static void assertEquals( Object a , Object b ){
 	_assertEquals( a , b );
     }

src/test/com/mongodb/ReadPreferenceTest.java

@@ -62,8 +62,8 @@ public ReadPreferenceTest() throws IOException, MongoException {
     @Test
     @SuppressWarnings("deprecation")
     public void testDeprecatedStaticMembers() {
-        assertEquals(ReadPreference.primary(), ReadPreference.PRIMARY);
-        assertEquals(ReadPreference.secondaryPreferred(), ReadPreference.SECONDARY);
+        assertSame(ReadPreference.primary(), ReadPreference.PRIMARY);
+        assertSame(ReadPreference.secondaryPreferred(), ReadPreference.SECONDARY);
     }
 
     @Test
@@ -76,7 +76,7 @@ public void testStaticPreferences() {
     }
 
     @Test
-    public void testPrimaryReadPreference(){
+    public void testPrimaryReadPreference() {
         assertEquals(_primary, ReadPreference.primary().getNode(_set));
         assertNull(ReadPreference.primary().getNode(_setNoPrimary));
         assertEquals("{ \"mode\" : \"primary\"}", ReadPreference.primary().toDBObject().toString());