Example with adding indexes from code and like annotation.

spring-data-mongodb/src/main/java/org/baeldung/model/User.java

@@ -1,7 +1,12 @@
 package org.baeldung.model;
 
 import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.index.CompoundIndex;
+import org.springframework.data.mongodb.core.index.CompoundIndexes;
+import org.springframework.data.mongodb.core.index.Indexed;
+import org.springframework.data.mongodb.core.mapping.DBRef;
 import org.springframework.data.mongodb.core.mapping.Document;
+import org.springframework.data.mongodb.core.mapping.Field;
 
 import com.mysema.query.annotations.QueryEntity;
 
@@ -13,6 +18,10 @@ public class User {
     private String id;
     private String name;
     private Integer age;
+    @DBRef
+    @Indexed
+    @Field("email")
+    private EmailAddress emailAddress;
 
     public String getId() {
         return id;
@@ -37,4 +46,12 @@ public class User {
     public void setAge(final Integer age) {
         this.age = age;
     }
+
+    public EmailAddress getEmailAddress() {
+        return emailAddress;
+    }
+
+    public void setEmailAddress(EmailAddress emailAddress) {
+        this.emailAddress = emailAddress;
+    }
 }

spring-data-mongodb/src/test/java/org/baeldung/repository/UserRepositoryIntegrationTest.java

@@ -6,6 +6,7 @@ import static org.junit.Assert.assertThat;
 import java.util.List;
 
 import org.baeldung.config.MongoConfig;
+import org.baeldung.model.EmailAddress;
 import org.baeldung.model.User;
 import org.junit.After;
 import org.junit.Before;
@@ -16,7 +17,10 @@ import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.Sort.Direction;
 import org.springframework.data.mongodb.core.MongoOperations;
+import org.springframework.data.mongodb.core.index.Index;
+import org.springframework.data.mongodb.core.index.IndexInfo;
 import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.test.context.ContextConfiguration;
@@ -145,4 +149,30 @@ public class UserRepositoryIntegrationTest {
         assertThat(users.size(), is(1));
         assertThat(page.getTotalPages(), is(2));
     }
+    
+    @Test
+    public void givenUserExistsWithIndexAddedFromMapping_whenCheckingIndex_thenIndexIsExisted() {
+        User user = new User();
+        user.setName("Brendan");
+        EmailAddress emailAddress = new EmailAddress("a@gmail.com");
+        mongoOps.insert(emailAddress);
+        user.setEmailAddress(emailAddress);
+        mongoOps.insert(user);
+        
+        List<IndexInfo> indexInfos = mongoOps.indexOps("user").getIndexInfo();
+
+        assertThat(indexInfos.size(), is(1));
+    }
+    
+    @Test
+    public void givenUserExistsWithIndexAddedFromCode_whenCheckingIndex_thenIndexIsExisted() {
+        User user = new User();
+        user.setName("Brendan");
+        mongoOps.indexOps(User.class).ensureIndex(new Index().on("name", Direction.ASC));
+        mongoOps.insert(user);
+        
+        List<IndexInfo> indexInfos = mongoOps.indexOps("user").getIndexInfo();
+
+        assertThat(indexInfos.size(), is(2));
+    }
 }