DATAMONGO-1421 - Fix serialization in error message causing error itself.

We now make sure to safely serialize the criteria object used for creating the error message when raising an `InvalidMongoDbApiUsageException` in cases where `addCriteria` is used to add multiple entries for the same property.

Original pull request: #448.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 the original author or authors.
+ * Copyright 2010-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -96,7 +96,7 @@ public class Query {
 		} else {
 			throw new InvalidMongoDbApiUsageException(
 					"Due to limitations of the com.mongodb.BasicDBObject, " + "you can't add a second '" + key + "' criteria. "
-							+ "Query already contains '" + existing.getCriteriaObject() + "'.");
+							+ "Query already contains '" + serializeToJsonSafely(existing.getCriteriaObject()) + "'.");
 		}
 
 		return this;

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

@@ -38,6 +38,7 @@ import org.springframework.data.mongodb.core.SpecialDoc;
  * @author Oliver Gierke
  * @author Patryk Wasik
  * @author Thomas Darimont
+ * @author Christoph Strobl
  */
 public class QueryTests {
 
@@ -213,4 +214,20 @@ public class QueryTests {
 		assertThat(query.getRestrictedTypes().size(), is(1));
 		assertThat(query.getRestrictedTypes(), hasItems(Arrays.asList(SpecialDoc.class).toArray(new Class<?>[0])));
 	}
+
+	@Test // DATAMONGO-1421
+	public void addCriteriaForSamePropertyMultipleTimesShouldThrowAndSafelySerializeErrorMessage() {
+
+		exception.expect(InvalidMongoDbApiUsageException.class);
+		exception.expectMessage("second 'value' criteria");
+		exception.expectMessage("already contains '{ \"value\" : { $java : VAL_1 } }'");
+
+		Query query = new Query();
+		query.addCriteria(where("value").is(EnumType.VAL_1));
+		query.addCriteria(where("value").is(EnumType.VAL_2));
+	}
+
+	enum EnumType {
+		VAL_1, VAL_2
+	}
 }