Allow custom ObjectMapper to be injected

Jackson-based session converter now allows a custom ObjectMapper to be injected.

Resolves #27.

Author: gregturn

src/main/java/org/springframework/session/data/mongo/JacksonMongoSessionConverter.java

@@ -28,6 +28,7 @@
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.security.jackson2.SecurityJackson2Modules;
 import org.springframework.session.FindByIndexNameSessionRepository;
+import org.springframework.util.Assert;
 
 import com.fasterxml.jackson.annotation.JsonAutoDetect;
 import com.fasterxml.jackson.annotation.PropertyAccessor;
@@ -65,6 +66,12 @@ public JacksonMongoSessionConverter(Iterable<Module> modules) {
 		this.objectMapper.registerModules(modules);
 	}
 
+	public JacksonMongoSessionConverter(ObjectMapper objectMapper) {
+
+		Assert.notNull(objectMapper, "ObjectMapper can NOT be null!");
+		this.objectMapper = objectMapper;
+	}
+
 	protected Query getQueryForIndex(String indexName, Object indexValue) {
 
 		if (FindByIndexNameSessionRepository.PRINCIPAL_NAME_INDEX_NAME.equals(indexName)) {

src/test/java/org/springframework/session/data/mongo/JacksonMongoSessionConverterTest.java

@@ -15,11 +15,16 @@
  */
 package org.springframework.session.data.mongo;
 
-import static org.assertj.core.api.Assertions.*;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+import java.lang.reflect.Field;
 
 import org.junit.Test;
+
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.util.ReflectionUtils;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import com.mongodb.DBObject;
 
 /**
@@ -59,5 +64,27 @@ public void shouldQueryAgainstAttribute() throws Exception {
 		assertThat(cart.getQueryObject().get("attrs.cart")).isEqualTo("my-cart");
 	}
 
+	@Test
+	public void shouldAllowCustomObjectMapper() {
+
+		// given
+		ObjectMapper myMapper = new ObjectMapper();
+
+		// when
+		JacksonMongoSessionConverter converter = new JacksonMongoSessionConverter(myMapper);
+
 
+		// then
+		Field objectMapperField = ReflectionUtils.findField(JacksonMongoSessionConverter.class, "objectMapper");
+		ReflectionUtils.makeAccessible(objectMapperField);
+		ObjectMapper converterMapper = (ObjectMapper) ReflectionUtils.getField(objectMapperField, converter);
+
+		assertThat(converterMapper).isEqualTo(myMapper);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void shouldNotAllowNullObjectMapperToBeInjected() {
+
+		new JacksonMongoSessionConverter((ObjectMapper) null);
+	}
 }