DATAMONGO-462 - Added custom converters for URL.

So far URL instances were treated as entities and serialized as nested document. As there was no custom converter registered to re-instantiate the objects and URL does not contain a no-arg constructor, reading the instances back in resulted in an ugly exception in ReflectionEntityInstantiator. We now register a custom Converter to serialize URL instances as their plain toString() representation. This causes the reading working out of the box as the StringToObjectConverter registered by default uses the constructor taking a String on URL accidentally. To make sure this still works we added an explicit StringToURLConverter to implement symmetric conversions.

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

@@ -38,6 +38,8 @@ import org.springframework.data.mongodb.core.convert.MongoConverters.BigDecimalT
 import org.springframework.data.mongodb.core.convert.MongoConverters.BigIntegerToStringConverter;
 import org.springframework.data.mongodb.core.convert.MongoConverters.StringToBigDecimalConverter;
 import org.springframework.data.mongodb.core.convert.MongoConverters.StringToBigIntegerConverter;
+import org.springframework.data.mongodb.core.convert.MongoConverters.StringToURLConverter;
+import org.springframework.data.mongodb.core.convert.MongoConverters.URLToStringConverter;
 import org.springframework.data.mongodb.core.mapping.MongoSimpleTypes;
 import org.springframework.util.Assert;
 
@@ -89,6 +91,8 @@ public class CustomConversions {
 		this.converters.add(StringToBigDecimalConverter.INSTANCE);
 		this.converters.add(BigIntegerToStringConverter.INSTANCE);
 		this.converters.add(StringToBigIntegerConverter.INSTANCE);
+		this.converters.add(URLToStringConverter.INSTANCE);
+		this.converters.add(StringToURLConverter.INSTANCE);
 		this.converters.addAll(converters);
 
 		for (Object c : this.converters) {

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

@@ -17,8 +17,12 @@ package org.springframework.data.mongodb.core.convert;
 
 import java.math.BigDecimal;
 import java.math.BigInteger;
+import java.net.MalformedURLException;
+import java.net.URL;
 
 import org.bson.types.ObjectId;
+import org.springframework.core.convert.ConversionFailedException;
+import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.util.StringUtils;
 
@@ -119,4 +123,28 @@ abstract class MongoConverters {
 			return StringUtils.hasText(source) ? new BigInteger(source) : null;
 		}
 	}
+
+	public static enum URLToStringConverter implements Converter<URL, String> {
+		INSTANCE;
+
+		public String convert(URL source) {
+			return source == null ? null : source.toString();
+		}
+	}
+
+	public static enum StringToURLConverter implements Converter<String, URL> {
+		INSTANCE;
+
+		private static final TypeDescriptor SOURCE = TypeDescriptor.valueOf(String.class);
+		private static final TypeDescriptor TARGET = TypeDescriptor.valueOf(URL.class);
+
+		public URL convert(String source) {
+
+			try {
+				return source == null ? null : new URL(source);
+			} catch (MalformedURLException e) {
+				throw new ConversionFailedException(SOURCE, TARGET, source, e);
+			}
+		}
+	}
 }

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

@@ -3,6 +3,7 @@ package org.springframework.data.mongodb.core.convert;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
+import java.net.URL;
 import java.text.DateFormat;
 import java.text.Format;
 import java.util.Arrays;
@@ -152,6 +153,25 @@ public class CustomConversionsUnitTests {
 		assertThat(conversions.isSimpleType(Binary.class), is(true));
 	}
 
+	/**
+	 * @see DATAMONGO-462
+	 */
+	@Test
+	public void hasWriteConverterForURL() {
+
+		CustomConversions conversions = new CustomConversions();
+		assertThat(conversions.hasCustomWriteTarget(URL.class), is(true));
+	}
+
+	/**
+	 * @see DATAMONGO-462
+	 */
+	@Test
+	public void readTargetForURL() {
+		CustomConversions conversions = new CustomConversions();
+		assertThat(conversions.hasCustomReadTarget(String.class, URL.class), is(true));
+	}
+
 	enum FormatToStringConverter implements Converter<Format, String> {
 		INSTANCE;
 

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

@@ -21,6 +21,7 @@ import static org.junit.Assert.*;
 
 import java.math.BigDecimal;
 import java.math.BigInteger;
+import java.net.URL;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -1034,6 +1035,30 @@ public class MappingMongoConverterUnitTests {
 		assertThat(readResult.iterator().next(), is(Map.class));
 	}
 
+	/**
+	 * @see DATAMONGO-462
+	 */
+	@Test
+	public void readsURLsAsStringsByDefault() throws Exception {
+		DBObject dbObject = new BasicDBObject("url", new URL("http://springsource.org"));
+		URLWrapper result = converter.read(URLWrapper.class, dbObject);
+		assertThat(result.url, is(new URL("http://springsource.org")));
+	}
+
+	/**
+	 * @see DATAMONGO-462
+	 */
+	@Test
+	public void writesURLsAsStringsByDefault() throws Exception {
+
+		URLWrapper wrapper = new URLWrapper();
+		wrapper.url = new URL("http://springsource.org");
+		DBObject sink = new BasicDBObject();
+
+		converter.write(wrapper, sink);
+		assertThat(sink.get("url"), is((Object) "http://springsource.org"));
+	}
+
 	static class GenericType<T> {
 		T content;
 	}
@@ -1165,6 +1190,10 @@ public class MappingMongoConverterUnitTests {
 		Object value;
 	}
 
+	static class URLWrapper {
+		URL url;
+	}
+
 	private class LocalDateToDateConverter implements Converter<LocalDate, Date> {
 
 		public Date convert(LocalDate source) {