DATADOC-171 - Convert BigDecimals to String by default.

Unfortunately MongoDB can't handle BigDecimal instances by default thus we have to provide a default serialization. We do by simply serializing it into a String and reading it back. Can be customized to register a custom Converter with the MongoConverter.

spring-data-mongodb/src/main/java/org/springframework/data/document/mongodb/convert/AbstractMongoConverter.java

@@ -16,6 +16,7 @@
 
 package org.springframework.data.document.mongodb.convert;
 
+import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -27,10 +28,12 @@ import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.support.ConversionServiceFactory;
 import org.springframework.core.convert.support.GenericConversionService;
-import org.springframework.data.document.mongodb.convert.ObjectIdConverters.BigIntegerToObjectIdConverter;
-import org.springframework.data.document.mongodb.convert.ObjectIdConverters.ObjectIdToBigIntegerConverter;
-import org.springframework.data.document.mongodb.convert.ObjectIdConverters.ObjectIdToStringConverter;
-import org.springframework.data.document.mongodb.convert.ObjectIdConverters.StringToObjectIdConverter;
+import org.springframework.data.document.mongodb.convert.MongoConverters.BigDecimalToStringConverter;
+import org.springframework.data.document.mongodb.convert.MongoConverters.BigIntegerToObjectIdConverter;
+import org.springframework.data.document.mongodb.convert.MongoConverters.ObjectIdToBigIntegerConverter;
+import org.springframework.data.document.mongodb.convert.MongoConverters.ObjectIdToStringConverter;
+import org.springframework.data.document.mongodb.convert.MongoConverters.StringToBigDecimalConverter;
+import org.springframework.data.document.mongodb.convert.MongoConverters.StringToObjectIdConverter;
 import com.mongodb.BasicDBList;
 import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;

spring-data-mongodb/src/main/java/org/springframework/data/document/mongodb/convert/CustomConversions.java

@@ -30,6 +30,8 @@ import org.springframework.core.convert.converter.ConverterFactory;
 import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.core.convert.converter.GenericConverter.ConvertiblePair;
 import org.springframework.core.convert.support.GenericConversionService;
+import org.springframework.data.document.mongodb.convert.MongoConverters.BigDecimalToStringConverter;
+import org.springframework.data.document.mongodb.convert.MongoConverters.StringToBigDecimalConverter;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
 import org.springframework.util.Assert;
 
@@ -76,16 +78,16 @@ public class CustomConversions {
 		this.writingPairs = new HashSet<ConvertiblePair>();
 		this.customSimpleTypes = new HashSet<Class<?>>();
 		
-		registerConversion(CustomToStringConverter.INSTANCE);
-		
-		for (Object c : converters) {
-			registerConversion(c);
-		}
-		
 		this.converters = new ArrayList<Object>();
 		this.converters.add(CustomToStringConverter.INSTANCE);
+		this.converters.add(BigDecimalToStringConverter.INSTANCE);
+		this.converters.add(StringToBigDecimalConverter.INSTANCE);
 		this.converters.addAll(converters);
 		
+		for (Object c : this.converters) {
+			registerConversion(c);
+		}
+		
 		this.simpleTypeHolder = new SimpleTypeHolder(customSimpleTypes, true);
 	}
 	

spring-data-mongodb/src/main/java/org/springframework/data/document/mongodb/convert/MongoConverters.java

@@ -15,22 +15,23 @@
  */
 package org.springframework.data.document.mongodb.convert;
 
+import java.math.BigDecimal;
 import java.math.BigInteger;
 
 import org.bson.types.ObjectId;
 import org.springframework.core.convert.converter.Converter;
 
 /**
- * Wrapper class to contain useful {@link ObjectId}-to-something-and-back converters.
+ * Wrapper class to contain useful converters for the usage with Mongo.
  * 
  * @author Oliver Gierke
  */
-abstract class ObjectIdConverters {
+abstract class MongoConverters {
 
 	/**
 	 * Private constructor to prevent instantiation.
 	 */
-	private ObjectIdConverters() {
+	private MongoConverters() {
 
 	}
 
@@ -85,4 +86,21 @@ abstract class ObjectIdConverters {
 			return new ObjectId(source.toString(16));
 		}
 	}
+
+
+	public static enum BigDecimalToStringConverter implements Converter<BigDecimal, String> {
+		INSTANCE;
+
+		public String convert(BigDecimal source) {
+			return source.toString();
+		}
+	}
+	
+	public static enum StringToBigDecimalConverter implements Converter<String, BigDecimal> {
+		INSTANCE;
+		
+		public BigDecimal convert(String source) {
+			return new BigDecimal(source);
+		}
+	}
 }

spring-data-mongodb/src/test/java/org/springframework/data/document/mongodb/convert/MappingMongoConverterUnitTests.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.data.document.mongodb.mapping;
+package org.springframework.data.document.mongodb.convert;
 
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
@@ -39,6 +39,8 @@ import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.document.mongodb.MongoDbFactory;
 import org.springframework.data.document.mongodb.convert.CustomConversions;
 import org.springframework.data.document.mongodb.convert.MappingMongoConverter;
+import org.springframework.data.document.mongodb.mapping.Field;
+import org.springframework.data.document.mongodb.mapping.MongoMappingContext;
 
 import com.mongodb.BasicDBList;
 import com.mongodb.BasicDBObject;
@@ -317,7 +319,7 @@ public class MappingMongoConverterUnitTests {
 	}
 	
 	/**
-	 * @see DATACMNS-42
+	 * @see DATACMNS-42, DATADOC-171
 	 */
 	@Test
 	public void writesClassWithBigDecimal() {
@@ -328,16 +330,17 @@ public class MappingMongoConverterUnitTests {
 		DBObject dbObject = new BasicDBObject();
 		converter.write(container, dbObject);
 		
-		assertThat(dbObject.get("value"), is((Object) container.value));
+		assertThat(dbObject.get("value"), is(instanceOf(String.class)));
+		assertThat((String) dbObject.get("value"), is("2.5"));
 	}
 	
 	/**
-	 * @see DATACMNS-42
+	 * @see DATACMNS-42, DATADOC-171
 	 */
 	@Test
 	public void readsClassWithBigDecimal() {
 		
-		DBObject dbObject = new BasicDBObject("value", 2.5d);
+		DBObject dbObject = new BasicDBObject("value", "2.5");
 		BigDecimalContainer result = converter.read(BigDecimalContainer.class, dbObject);
 		
 		assertThat(result.value, is(BigDecimal.valueOf(2.5d)));
@@ -358,7 +361,6 @@ public class MappingMongoConverterUnitTests {
 		
 		BasicDBList typedOuterString = (BasicDBList) outerStrings;
 		assertThat(typedOuterString.size(), is(1));
-		
 	}
 	
 	class ClassWithEnumProperty {

spring-data-mongodb/src/test/java/org/springframework/data/document/mongodb/convert/MongoConvertersUnitTests.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2011 by the original author(s).
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.document.mongodb.convert;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
+import java.math.BigDecimal;
+
+import org.junit.Test;
+import org.springframework.data.document.mongodb.convert.MongoConverters.BigDecimalToStringConverter;
+import org.springframework.data.document.mongodb.convert.MongoConverters.StringToBigDecimalConverter;
+
+/**
+ * Unit tests for {@link MongoConverters}.
+ *
+ * @author Oliver Gierke
+ */
+public class MongoConvertersUnitTests {
+
+	@Test
+	public void convertsBigDecimalToStringAndBackCorrectly() {
+		
+		BigDecimal bigDecimal = BigDecimal.valueOf(254, 1);
+		String value = BigDecimalToStringConverter.INSTANCE.convert(bigDecimal);
+		assertThat(value, is("25.4"));
+		
+		BigDecimal reference = StringToBigDecimalConverter.INSTANCE.convert(value);
+		assertThat(reference, is(bigDecimal));
+	}
+}