Added support for searchSimilar in ElasticsearchRepository

https://github.com/BioMedCentralLtd/spring-data-elasticsearch/issues/4

src/main/java/org/springframework/data/elasticsearch/repository/ElasticsearchRepository.java

@@ -22,7 +22,6 @@ import org.springframework.data.elasticsearch.core.query.SearchQuery;
 import org.springframework.data.repository.NoRepositoryBean;
 
 import java.io.Serializable;
-import java.util.List;
 
 /**
  * @param <T>
@@ -41,4 +40,6 @@ public interface ElasticsearchRepository<T, ID extends Serializable> extends Ela
     Page<T> search(QueryBuilder elasticsearchQuery, Pageable pageable);
 
     Page<T> search(SearchQuery searchQuery);
+
+    Page<T> searchSimilar(T entity);
 }

src/main/java/org/springframework/data/elasticsearch/repository/support/SimpleElasticsearchRepository.java

@@ -19,14 +19,10 @@ import org.elasticsearch.index.query.QueryBuilder;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.domain.*;
 import org.springframework.data.elasticsearch.core.ElasticsearchOperations;
-import org.springframework.data.elasticsearch.core.query.DeleteQuery;
-import org.springframework.data.elasticsearch.core.query.GetQuery;
-import org.springframework.data.elasticsearch.core.query.IndexQuery;
-import org.springframework.data.elasticsearch.core.query.SearchQuery;
+import org.springframework.data.elasticsearch.core.query.*;
 import org.springframework.data.elasticsearch.repository.ElasticsearchRepository;
 import org.springframework.util.Assert;
 
-import javax.annotation.PostConstruct;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.util.ArrayList;
@@ -187,6 +183,14 @@ public class SimpleElasticsearchRepository<T> implements ElasticsearchRepository
         return elasticsearchOperations.queryForPage(query, getEntityClass());
     }
 
+    @Override
+    public Page<T> searchSimilar(T entity) {
+        Assert.notNull(entity, "Cannot search similar records for 'null'.");
+        MoreLikeThisQuery query = new MoreLikeThisQuery();
+        query.setId(extractIdFromBean(entity));
+        return elasticsearchOperations.moreLikeThis(query, getEntityClass());
+    }
+
     @Override
     public void delete(String id) {
         Assert.notNull(id, "Cannot delete entity with id 'null'.");

src/test/java/org/springframework/data/elasticsearch/repositories/RepositoryTest.java

@@ -29,7 +29,9 @@ import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
 import javax.annotation.Resource;
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
 
 import static org.apache.commons.lang.RandomStringUtils.randomNumeric;
 import static org.elasticsearch.index.query.QueryBuilders.*;
@@ -381,4 +383,40 @@ public class RepositoryTest {
         //then
         assertThat(sampleEntities,is(notNullValue()));
     }
+
+
+    @Test
+    public void shouldReturnSimilarEntities(){
+        //given
+        String sampleMessage = "So we build a web site or an application and want to add search to it, " +
+                "and then it hits us: getting search working is hard. We want our search solution to be fast," +
+                " we want a painless setup and a completely free search schema, we want to be able to index data simply using JSON over HTTP, " +
+                "we want our search server to be always available, we want to be able to start with one machine and scale to hundreds, " +
+                "we want real-time search, we want simple multi-tenancy, and we want a solution that is built for the cloud.";
+
+
+
+        List<SampleEntity> sampleEntities = createSampleEntitiesWithMessage(sampleMessage, 30);
+        repository.save(sampleEntities);
+
+        //when
+        Page<SampleEntity> results = repository.searchSimilar(sampleEntities.get(0));
+
+        //then
+        assertThat(results.getTotalElements(), is(greaterThanOrEqualTo(1L)));
+    }
+
+    private static List<SampleEntity> createSampleEntitiesWithMessage(String message, int numberOfEntities){
+        List<SampleEntity> sampleEntities = new ArrayList<SampleEntity>();
+        for(int i = 0; i < numberOfEntities; i++){
+            String documentId = randomNumeric(5);
+            SampleEntity sampleEntity = new SampleEntity();
+            sampleEntity.setId(documentId);
+            sampleEntity.setMessage(message);
+            sampleEntity.setVersion(System.currentTimeMillis());
+            sampleEntities.add(sampleEntity);
+        }
+        return sampleEntities;
+    }
+
 }