REOPENED - BATCH-900: Retreive null values from the ExecutionContext

putting null value now equals removing entry for given key

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/ExecutionContext.java

@@ -29,19 +29,14 @@ import org.springframework.util.Assert;
  * for a map that allows optionally for type safety on reads. It also allows for
  * dirty checking by setting a 'dirty' flag whenever any put is called.
  * 
+ * Note that putting <code>null</code> value is equivalent to removing the entry
+ * for the given key.
+ * 
  * @author Lucas Ward
  * @author Douglas Kaminsky
  */
 public class ExecutionContext implements Serializable {
 
-	/**
-	 * Underlying {@link ConcurrentHashMap} does not accept <code>null</code>
-	 * values, so we convert it to a private constant under the covers.
-	 */
-	private static enum Constants {
-		NULL
-	};
-
 	private volatile boolean dirty = false;
 
 	private final Map<String, Object> map;
@@ -111,7 +106,8 @@ public class ExecutionContext implements Serializable {
 	}
 
 	/**
-	 * Add an Object value to the context (must be Serializable).
+	 * Add an Object value to the context (must be Serializable). Putting
+	 * <code>null</code> value for a given key removes the key.
 	 * 
 	 * @param key Key to add to context
 	 * @param value Value to associate with key
@@ -119,12 +115,12 @@ public class ExecutionContext implements Serializable {
 	public void put(String key, Object value) {
 		if (value != null) {
 			Assert.isInstanceOf(Serializable.class, value, "Value: [ " + value + "must be serializable.");
+			map.put(key, value);
 		}
 		else {
-			value = Constants.NULL;
+			map.remove(key);
 		}
 		dirty = true;
-		map.put(key, value);
 	}
 
 	/**
@@ -228,13 +224,7 @@ public class ExecutionContext implements Serializable {
 	 * @return The value represented by the given key
 	 */
 	public Object get(String key) {
-		Object value = map.get(key);
-		if (value == Constants.NULL) {
-			return null;
-		}
-		else {
-			return value;
-		}
+		return map.get(key);
 	}
 
 	/**
@@ -249,10 +239,6 @@ public class ExecutionContext implements Serializable {
 
 		Object value = map.get(key);
 
-		if (value == Constants.NULL) {
-			return null;
-		}
-
 		if (!type.isInstance(value)) {
 			throw new ClassCastException("Value for key=[" + key + "] is not of type: [" + type + "], it is ["
 					+ (value == null ? null : "(" + value.getClass() + ")" + value) + "]");

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/ExecutionContextTests.java

@@ -27,7 +27,7 @@ import org.junit.Test;
 
 /**
  * @author Lucas Ward
- *
+ * 
  */
 public class ExecutionContextTests {
 
@@ -37,15 +37,15 @@ public class ExecutionContextTests {
 	public void setUp() throws Exception {
 		context = new ExecutionContext();
 	}
-	
+
 	@Test
-	public void testNormalUsage(){
-		
+	public void testNormalUsage() {
+
 		context.putString("1", "testString1");
 		context.putString("2", "testString2");
 		context.putLong("3", 3);
 		context.putDouble("4", 4.4);
-		
+
 		assertEquals("testString1", context.getString("1"));
 		assertEquals("testString2", context.getString("2"));
 		assertEquals("defaultString", context.getString("5", "defaultString"));
@@ -54,96 +54,99 @@ public class ExecutionContextTests {
 		assertEquals(3, context.getLong("3"));
 		assertEquals(5, context.getLong("5", 5));
 	}
-	
+
 	@Test
-	public void testInvalidCast(){
-		
+	public void testInvalidCast() {
+
 		context.putLong("1", 1);
-		try{
+		try {
 			context.getDouble("1");
 			fail();
 		}
-		catch(ClassCastException ex){
-			//expected
+		catch (ClassCastException ex) {
+			// expected
 		}
 	}
-	
+
 	@Test
-	public void testIsEmpty(){
+	public void testIsEmpty() {
 		assertTrue(context.isEmpty());
 		context.putString("1", "test");
 		assertFalse(context.isEmpty());
 	}
-	
+
 	@Test
-	public void testDirtyFlag(){
+	public void testDirtyFlag() {
 		assertFalse(context.isDirty());
 		context.putString("1", "test");
 		assertTrue(context.isDirty());
 		context.clearDirtyFlag();
 		assertFalse(context.isDirty());
 	}
-	
+
 	@Test
-	public void testContains(){
+	public void testContains() {
 		context.putString("1", "testString");
 		assertTrue(context.containsKey("1"));
 		assertTrue(context.containsValue("testString"));
 	}
-	
+
 	@Test
-	public void testEquals(){
+	public void testEquals() {
 		context.putString("1", "testString");
 		ExecutionContext tempContext = new ExecutionContext();
 		assertFalse(tempContext.equals(context));
 		tempContext.putString("1", "testString");
 		assertTrue(tempContext.equals(context));
 	}
-	
+
 	@Test
-	public void testSerializationCheck(){
-		//adding a non serializable object should cause an error.
-		try{
+	public void testSerializationCheck() {
+		// adding a non serializable object should cause an error.
+		try {
 			context.put("1", new Object());
 			fail();
 		}
-		catch(IllegalArgumentException ex){
-			//expected
+		catch (IllegalArgumentException ex) {
+			// expected
 		}
 	}
-	
+
+	/**
+	 * Putting null value is equivalent to removing the entry for the given key.
+	 */
 	@Test
-	public void testPutNull(){
-		//putting null should work
+	public void testPutNull() {
 		context.put("1", null);
 		assertNull(context.get("1"));
+		assertFalse(context.containsKey("1"));
 	}
-	
+
 	@Test
 	public void testGetNull() {
 		assertNull(context.get("does not exist"));
 	}
-	
+
 	@Test
 	public void testSerialization() {
-		
+
 		TestSerializable s = new TestSerializable();
 		s.value = 7;
-		
+
 		context.putString("1", "testString1");
 		context.putString("2", "testString2");
 		context.putLong("3", 3);
 		context.putDouble("4", 4.4);
 		context.put("5", s);
-		
+
 		byte[] serialized = SerializationUtils.serialize(context);
-		
+
 		ExecutionContext deserialized = (ExecutionContext) SerializationUtils.deserialize(serialized);
-		
+
 		assertEquals(context, deserialized);
-		assertEquals(7, ((TestSerializable)deserialized.get("5")).value);
+		assertEquals(7, ((TestSerializable) deserialized.get("5")).value);
 	}
-	
+
 	@Test
 	public void testCopyConstructor() throws Exception {
 		ExecutionContext context = new ExecutionContext();
@@ -151,13 +154,13 @@ public class ExecutionContextTests {
 		ExecutionContext copy = new ExecutionContext(context);
 		assertEquals(copy, context);
 	}
-	
+
 	@Test
 	public void testCopyConstructorNullnNput() throws Exception {
-		ExecutionContext context = new ExecutionContext((ExecutionContext)null);
+		ExecutionContext context = new ExecutionContext((ExecutionContext) null);
 		assertTrue(context.isEmpty());
 	}
-	
+
 	/**
 	 * Value object for testing serialization
 	 */
@@ -172,9 +175,7 @@ public class ExecutionContextTests {
 		public int hashCode() {
 			return HashCodeBuilder.reflectionHashCode(this);
 		}
-		
-		
-		
+
 	}
-	
+
 }