DATAMONGO-551 - MongoTemplate can now persist plain Strings if they are valid JSON.

Added some code to MongoTemplate that inspects the object to be saved for being a String. If it is we try to parse the given String into a JSON document and continue as if we had been given a DBObject initially. Non-parseable Strings are rejected with a MappingException.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoTemplate.java

@@ -101,6 +101,7 @@ import com.mongodb.ReadPreference;
 import com.mongodb.WriteConcern;
 import com.mongodb.WriteResult;
 import com.mongodb.util.JSON;
+import com.mongodb.util.JSONParseException;
 
 /**
  * Primary implementation of {@link MongoOperations}.
@@ -790,6 +791,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 		}
 	}
 
+	@SuppressWarnings("unchecked")
 	protected <T> void doSave(String collectionName, T objectToSave, MongoWriter<T> writer) {
 
 		assertUpdateableIdIfNotSet(objectToSave);
@@ -797,7 +799,16 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 		DBObject dbDoc = new BasicDBObject();
 
 		maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave));
-		writer.write(objectToSave, dbDoc);
+
+		if (!(objectToSave instanceof String)) {
+			writer.write(objectToSave, dbDoc);
+		} else {
+			try {
+				objectToSave = (T) JSON.parse((String) objectToSave);
+			} catch (JSONParseException e) {
+				throw new MappingException("Could not parse given String to save into a JSON document!", e);
+			}
+		}
 
 		maybeEmitEvent(new BeforeSaveEvent<T>(objectToSave, dbDoc));
 		Object id = saveDBObject(collectionName, dbDoc, objectToSave.getClass());

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/MongoTemplateTests.java

@@ -1393,6 +1393,22 @@ public class MongoTemplateTests {
 		assertThat(result.get("_id"), is(dbObject.get("_id")));
 	}
 
+	/**
+	 * @see DATAMONGO-551
+	 */
+	@Test
+	public void writesPlainString() {
+		template.save("{ 'foo' : 'bar' }", "collection");
+	}
+
+	/**
+	 * @see DATAMONGO-551
+	 */
+	@Test(expected = MappingException.class)
+	public void rejectsNonJsonStringForSave() {
+		template.save("Foobar!", "collection");
+	}
+
 	static class MyId {
 
 		String first;