Add missing transformation to ensure String

Author: jtnelson

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 #### Version 1.3.1 (TBD)
 * Fixed some bugs related to serializing and deserializing some built-in `Transformers`.
+* Added missing transformers to ensure values are handled as Strings.
 
 #### Version 1.3.0 (November 23, 2018)
 * Added the `ScriptedTransformer` framework. `ScriptedTransformer` is abstract class that can be extended to provide transformation logic via a script that is compatible with the Java script engine platform. Right now, javascript is the supported language for writing transformer scripts.

src/main/java/com/cinchapi/etl/Transformers.java

@@ -202,26 +202,6 @@ public static Transformer keyMap(Map<String, String> map) {
         };
     }
 
-    /**
-     * Return a {@link Transformer} that replaces whitespace characters with an
-     * underscore in keys.
-     * 
-     * @return the {@link Transformer}
-     */
-    public static Transformer keyWhitespaceToUnderscore() {
-        return keyReplaceChars(ImmutableMap.of(' ', '_'));
-    }
-
-    /**
-     * Return a {@link Transformer} that removes all whitespace characters from
-     * a key.
-     * 
-     * @return the {@link Transformer}
-     */
-    public static Transformer keyRemoveWhitespace() {
-        return keyRemoveInvalidChars(Character::isWhitespace);
-    }
-
     /**
      * Return a {@link Transformer} that removes all the character in the
      * {@code invalid} collection.
@@ -269,6 +249,16 @@ public static Transformer keyRemoveInvalidChars(
         };
     }
 
+    /**
+     * Return a {@link Transformer} that removes all whitespace characters from
+     * a key.
+     * 
+     * @return the {@link Transformer}
+     */
+    public static Transformer keyRemoveWhitespace() {
+        return keyRemoveInvalidChars(Character::isWhitespace);
+    }
+
     /**
      * Return a {@link Transformer} that replaces all the character keys in the
      * {@code replacements} mapping with their associated character values in
@@ -366,6 +356,16 @@ public static Transformer keyValueStripQuotes() {
         return keyValueRemoveQuotes();
     }
 
+    /**
+     * Return a {@link Transformer} that replaces whitespace characters with an
+     * underscore in keys.
+     * 
+     * @return the {@link Transformer}
+     */
+    public static Transformer keyWhitespaceToUnderscore() {
+        return keyReplaceChars(ImmutableMap.of(' ', '_'));
+    }
+
     /**
      * Return a {@link Transformer} that does not perform any key or value
      * transformations.
@@ -388,10 +388,6 @@ public static Transformer nullSafe(Transformer transformer) {
                 : null;
     }
 
-    public static Transformer valueRemoveIfEmpty() {
-        return valueRemoveIf(Empty.ness());
-    }
-
     /**
      * Return a {@link Transformer} that will cause a key/value pair to be
      * "removed" if the value is described by the provided {@code adjective}.
@@ -408,21 +404,6 @@ public static Transformer removeValuesThatAre(Adjective adjective) {
         return valueRemoveIf(adjective);
     }
 
-    /**
-     * Return a {@link Transformer} that will cause a key/value pair to be
-     * "removed" if the value is described by the provided {@code adjective}.
-     * <p>
-     * Removal is accomplished by returning an empty map for the transformation.
-     * </p>
-     * 
-     * @param adjective
-     * @return the {@link Transformer}
-     */
-    public static Transformer valueRemoveIf(Adjective adjective) {
-        return (key, value) -> adjective.describes(value) ? ImmutableMap.of()
-                : null;
-    }
-
     /**
      * Return a {@link Transformer} that, For EVERY key, transform values to a
      * {@link Boolean} if possible. If the value cannot be transformed, an
@@ -564,6 +545,41 @@ public static Transformer valueAsResolvableLinkInstruction(String... keys) {
         }
     }
 
+    /**
+     * Return a {@link Transformer} that, for EVERY key, transforms values to a
+     * {@link String}.
+     * 
+     * @return the {@link Transformer}
+     */
+    public static Transformer valueAsString() {
+        return (key, value) -> value instanceof String ? null
+                : Transformation.to(key, value.toString());
+    }
+
+    /**
+     * Return a {@link Transformer} that, for the specified {@code key}as,
+     * transforms values to a {@link String}.
+     * 
+     * @param keys
+     * @return the {@link Transformer}
+     */
+    public static Transformer valueAsString(String... keys) {
+        if(keys.length == 0) {
+            return valueAsString();
+        }
+        else {
+            Set<String> _keys = Arrays.stream(keys).collect(Collectors.toSet());
+            return (key, value) -> {
+                if(_keys.contains(key)) {
+                    return valueAsString().transform(key, value);
+                }
+                else {
+                    return null;
+                }
+            };
+        }
+    }
+
     /**
      * Return a {@link Transformer} that, For EVERY key, transform values to a
      * {@link Number} if possible. If the value cannot be transformed, an
@@ -687,6 +703,25 @@ public static Transformer valueNullifyIfEmpty(Empty empty) {
         };
     }
 
+    /**
+     * Return a {@link Transformer} that will cause a key/value pair to be
+     * "removed" if the value is described by the provided {@code adjective}.
+     * <p>
+     * Removal is accomplished by returning an empty map for the transformation.
+     * </p>
+     * 
+     * @param adjective
+     * @return the {@link Transformer}
+     */
+    public static Transformer valueRemoveIf(Adjective adjective) {
+        return (key, value) -> adjective.describes(value) ? ImmutableMap.of()
+                : null;
+    }
+
+    public static Transformer valueRemoveIfEmpty() {
+        return valueRemoveIf(Empty.ness());
+    }
+
     /**
      * Return a {@link Transformer} that splits a String value into multiple
      * strings that are all mapped from the original key.

src/test/java/com/cinchapi/etl/TransformersTest.java

@@ -127,6 +127,14 @@ public void testValueAsTag() {
         Object value = Iterables.getOnlyElement(transformed.values());
         Assert.assertTrue(value instanceof Tag);
     }
+    
+    @Test
+    public void testValueAsString() {
+        Map<String, Object> transformed = Transformers.valueAsString()
+                .transform("foo", (Object) 1);
+        Object value = Iterables.getOnlyElement(transformed.values());
+        Assert.assertTrue(value instanceof String);
+    }
 
     @Test
     public void testValueNullifyIfEmpty() {