Author: julius
Date: Thu Aug 23 14:28:14 2012
New Revision: 1376505
URL: http://svn.apache.org/viewvc?rev=1376505&view=rev
Log:
[LANG-816] introduce CONST() methods to prevent Javac from inlining constants
Modified:
commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/ObjectUtils.java
commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/ObjectUtilsTest.java
Modified:
commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/ObjectUtils.java
URL:
http://svn.apache.org/viewvc/commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/ObjectUtils.java?rev=1376505&r1=1376504&r2=1376505&view=diff
==============================================================================
---
commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/ObjectUtils.java
(original)
+++
commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/ObjectUtils.java
Thu Aug 23 14:28:14 2012
@@ -605,4 +605,170 @@ public class ObjectUtils {
}
}
+
+ // Constants (LANG-816):
+ /*
+ These methods ensure constants are not inlined by javac.
+ For example, typically a developer might declare a constant like so:
+
+ public final static int MAGIC_NUMBER = 5;
+
+ Should a different jar file refer to this, and the MAGIC_NUMBER
+ is changed a later date (e.g., MAGIC_NUMBER = 6), the different jar
+ file will need to recompile itself. This is because javac
+ typically inlines the primitive or String constant directly into
+ the bytecode, and removes the reference to the MAGIC_NUMBER field.
+
+ To help the other jar (so that it does not need to recompile
+ when constants are changed) the original developer can declare
+ their constant using one of the CONST() utility methods, instead:
+
+ public final static int MAGIC_NUMBER = CONST(5);
+ */
+
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static boolean MAGIC_FLAG = CONST(true);
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the boolean value to return
+ * @return the boolean v, unchanged
+ */
+ public static boolean CONST(final boolean v) { return v; }
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static byte MAGIC_BYTE = CONST(127);
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the byte value to return
+ * @return the byte v, unchanged
+ */
+ public static byte CONST(final byte v) { return v; }
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static byte MAGIC_CHAR = CONST('a');
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the char value to return
+ * @return the char v, unchanged
+ */
+ public static char CONST(final char v) { return v; }
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static byte MAGIC_SHORT = CONST(123);
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the short value to return
+ * @return the short v, unchanged
+ */
+ public static short CONST(final short v) { return v; }
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static byte MAGIC_INT = CONST(123);
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the int value to return
+ * @return the int v, unchanged
+ */
+ public static int CONST(final int v) { return v; }
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static byte MAGIC_LONG = CONST(123L);
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the long value to return
+ * @return the long v, unchanged
+ */
+ public static long CONST(final long v) { return v; }
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static byte MAGIC_FLOAT = CONST(1.0f);
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the float value to return
+ * @return the float v, unchanged
+ */
+ public static float CONST(final float v) { return v; }
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static byte MAGIC_DOUBLE = CONST(1.0);
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the double value to return
+ * @return the double v, unchanged
+ */
+ public static double CONST(final double v) { return v; }
+
+ /**
+ * This method returns the provided value unchanged.
+ * This can prevent javac from inlining a constant
+ * field, e.g.,
+ *
+ * public final static byte MAGIC_STRING = CONST("abc");
+ *
+ * This way any jars that refer to this field do not
+ * have to recompile themselves if the field's value
+ * changes at some future date.
+ *
+ * @param v the genericized Object value to return (typically a String).
+ * @return the genericized Object v, unchanged (typically a String).
+ */
+ public static <T> T CONST(final T v) { return v; }
+
}
Modified:
commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/ObjectUtilsTest.java
URL:
http://svn.apache.org/viewvc/commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/ObjectUtilsTest.java?rev=1376505&r1=1376504&r2=1376505&view=diff
==============================================================================
---
commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/ObjectUtilsTest.java
(original)
+++
commons/proper/lang/trunk/src/test/java/org/apache/commons/lang3/ObjectUtilsTest.java
Thu Aug 23 14:28:14 2012
@@ -450,6 +450,24 @@ public class ObjectUtilsTest {
}
}
+ @Test
+ public void testConstMethods() {
+
+ // To truly test the CONST() method, we'd want to look in the
+ // bytecode to see if the literals were folded into the
+ // class, or if the bytecode kept the method call.
+
+ assertEquals("CONST(boolean)", true, ObjectUtils.CONST(true));
+ assertEquals("CONST(byte)", (byte) 3, ObjectUtils.CONST((byte) 3));
+ assertEquals("CONST(char)", (char) 3, ObjectUtils.CONST((char) 3));
+ assertEquals("CONST(short)", (short) 3, ObjectUtils.CONST((short) 3));
+ assertEquals("CONST(int)", 3, ObjectUtils.CONST(3));
+ assertEquals("CONST(long)", 3l, ObjectUtils.CONST(3l));
+ assertEquals("CONST(float)", 3f, ObjectUtils.CONST(3f), 0);
+ assertEquals("CONST(double)", 3.0, ObjectUtils.CONST(3.0), 0);
+ assertEquals("CONST(Object)", "abc", ObjectUtils.CONST("abc"));
+ }
+
/**
* String that is cloneable.
*/
