Added Document#get("key", defaultValue) method

JAVA-2504

Author: rozza

bson/src/main/org/bson/Document.java

@@ -140,6 +140,25 @@ public <T> T get(final Object key, final Class<T> clazz) {
         return clazz.cast(documentAsMap.get(key));
     }
 
+    /**
+     * Gets the value of the given key, casting it to {@code Class<T>} or returning the default value if null.
+     * This is useful to avoid having casts in client code, though the effect is the same.
+     *
+     * @param key   the key
+     * @param defaultValue what to return if the value is null
+     * @param <T>   the type of the class
+     * @return the value of the given key, or null if the instance does not contain this key.
+     * @throws ClassCastException if the value of the given key is not of type T
+     * @since 3.5
+     */
+    @SuppressWarnings("unchecked")
+    public <T> T get(final Object key, final T defaultValue) {
+        notNull("defaultValue", defaultValue);
+        Class<T> clazz = notNull("clazz", (Class<T>) defaultValue.getClass());
+        Object value = documentAsMap.get(key);
+        return value == null ? defaultValue : clazz.cast(value);
+    }
+
     /**
      * Gets the value of the given key as an Integer.
      *
@@ -160,8 +179,7 @@ public Integer getInteger(final Object key) {
      * @throws java.lang.ClassCastException if the value is not an integer
      */
     public int getInteger(final Object key, final int defaultValue) {
-        Object value = get(key);
-        return value == null ? defaultValue : (Integer) value;
+        return get(key, defaultValue);
     }
 
     /**
@@ -217,8 +235,7 @@ public Boolean getBoolean(final Object key) {
      * @throws java.lang.ClassCastException if the value is not a boolean
      */
     public boolean getBoolean(final Object key, final boolean defaultValue) {
-        Object value = get(key);
-        return value == null ? defaultValue : (Boolean) value;
+        return get(key, defaultValue);
     }
 
     /**

bson/src/test/unit/org/bson/types/DocumentSpecification.groovy

@@ -37,14 +37,32 @@ class DocumentSpecification extends Specification {
                 .append('objectId', objectId).append('date', date);
 
         then:
-        doc.getInteger('int') == 1;
-        doc.getLong('long') == 2L;
-        doc.getDouble('double') == 3.0d;
-        doc.getString('string') == 'hi';
-        doc.getBoolean('boolean');
-        doc.getObjectId('objectId') == objectId;
-        doc.getDate('date') == date;
-        doc.get('objectId', ObjectId) == objectId;
+        doc.getInteger('int') == 1
+        doc.getInteger('intNoVal', 42) == 42
+        doc.getLong('long') == 2L
+        doc.getDouble('double') == 3.0d
+        doc.getString('string') == 'hi'
+        doc.getBoolean('boolean')
+        doc.getBoolean('booleanNoVal', true)
+        doc.getObjectId('objectId') == objectId
+        doc.getDate('date') == date
+
+
+        doc.get('objectId', ObjectId) == objectId
+        doc.get('int', Integer) == 1
+        doc.get('long', Long) == 2L
+        doc.get('double', Double) == 3.0d
+        doc.get('string', String) == 'hi'
+        doc.get('boolean', Boolean)
+        doc.get('date', Date) == date
+
+        doc.get('noVal', 42L) == 42L
+        doc.get('noVal', 3.1d) == 3.1d
+        doc.get('noVal', 'defVal') == 'defVal'
+        doc.get('noVal', true)
+        doc.get('noVal', objectId) == objectId
+        doc.get('noVal', date) == date
+        doc.get('noVal', objectId) == objectId
     }
 
     def 'should parse a valid JSON string to a Document'() {