Refactor MappingElasticsearchConverter.

* Add support for SpEL expressions via @value.
* Simplify readCollectionOrArray to consider properly nested lists and maps
* Simplify readMap to allow reading generic maps and entities in maps.
* Report a fallback TypeInformation in DefaultElasticsearchTypeMapper to properly convert nested maps.

We now no longer rely on isSimpleType when writing Maps. This is the preparation to consider Map as simple type.

Resolves spring-projects#1676.
See spring-projects#1675.

(cherry picked from commit 877de9c)

Author: mp911de

src/main/java/org/springframework/data/elasticsearch/core/convert/DefaultElasticsearchTypeMapper.java

@@ -26,6 +26,8 @@
 import org.springframework.data.mapping.Alias;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.context.MappingContext;
+import org.springframework.data.util.ClassTypeInformation;
+import org.springframework.data.util.TypeInformation;
 import org.springframework.lang.Nullable;
 
 /**
@@ -38,6 +40,9 @@
 public class DefaultElasticsearchTypeMapper extends DefaultTypeMapper<Map<String, Object>>
 		implements ElasticsearchTypeMapper {
 
+	@SuppressWarnings("rawtypes") //
+	private static final TypeInformation<Map> MAP_TYPE_INFO = ClassTypeInformation.from(Map.class);
+
 	private final @Nullable String typeKey;
 
 	public DefaultElasticsearchTypeMapper(@Nullable String typeKey) {
@@ -62,11 +67,23 @@ public DefaultElasticsearchTypeMapper(@Nullable String typeKey, TypeAliasAccesso
 		this.typeKey = typeKey;
 	}
 
-	@Override
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.convert.MongoTypeMapper#isTypeKey(java.lang.String)
+	 */
 	public boolean isTypeKey(String key) {
 		return typeKey != null && typeKey.equals(key);
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.convert.DefaultTypeMapper#getFallbackTypeFor(java.lang.Object)
+	 */
+	@Override
+	protected TypeInformation<?> getFallbackTypeFor(Map<String, Object> source) {
+		return MAP_TYPE_INFO;
+	}
+
 	/**
 	 * {@link TypeAliasAccessor} to store aliases in a {@link Map}.
 	 *