DATAMONGO-2327 - Add toJson method to Querydsl query support.

This allows to obtain the raw Json representation of the query for eg. debug usage.
We also updated the toString method to return a full Mongo Shell compatible representation of the query including projections, order, skip and limit.

Original pull request: #774.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/QuerydslAbstractMongodbQuery.java

@@ -18,6 +18,8 @@ package org.springframework.data.mongodb.repository.support;
 import java.util.List;
 
 import org.bson.Document;
+import org.bson.json.JsonMode;
+import org.bson.json.JsonWriterSettings;
 import org.springframework.lang.Nullable;
 
 import com.querydsl.core.DefaultQueryMetadata;
@@ -48,6 +50,9 @@ import com.querydsl.core.types.Predicate;
 public abstract class QuerydslAbstractMongodbQuery<K, Q extends QuerydslAbstractMongodbQuery<K, Q>>
 		implements SimpleQuery<Q> {
 
+	private static final JsonWriterSettings JSON_WRITER_SETTINGS = JsonWriterSettings.builder().outputMode(JsonMode.SHELL)
+			.build();
+
 	private final MongodbDocumentSerializer serializer;
 	private final QueryMixin<Q> queryMixin;
 
@@ -195,8 +200,65 @@ public abstract class QuerydslAbstractMongodbQuery<K, Q extends QuerydslAbstract
 		return createQuery(queryMixin.getMetadata().getWhere());
 	}
 
+	/**
+	 * Returns the {@literal Mongo Shell} representation of the query. <br />
+	 * The following query
+	 *
+	 * <pre class="code">
+	 *
+	 * where(p.lastname.eq("Matthews")).orderBy(p.firstname.asc()).offset(1).limit(5);
+	 * </pre>
+	 *
+	 * results in
+	 *
+	 * <pre class="code">
+	 *
+	 * find({"lastname" : "Matthews"}).sort({"firstname" : 1}).skip(1).limit(5)
+	 * </pre>
+	 *
+	 * @return never {@literal null}.
+	 */
 	@Override
 	public String toString() {
-		return asDocument().toString();
+
+		Document projection = createProjection(queryMixin.getMetadata().getProjection());
+		Document sort = createSort(queryMixin.getMetadata().getOrderBy());
+
+		StringBuilder sb = new StringBuilder("find(" + asDocument().toJson(JSON_WRITER_SETTINGS));
+		if (!projection.isEmpty()) {
+			sb.append(", " + projection.toJson(JSON_WRITER_SETTINGS));
+		}
+		sb.append(")");
+		if (!sort.isEmpty()) {
+			sb.append(".sort(" + sort.toJson(JSON_WRITER_SETTINGS) + ")");
+		}
+		if (queryMixin.getMetadata().getModifiers().getOffset() != null) {
+			sb.append(".skip(" + queryMixin.getMetadata().getModifiers().getOffset() + ")");
+		}
+		if (queryMixin.getMetadata().getModifiers().getLimit() != null) {
+			sb.append(".limit(" + queryMixin.getMetadata().getModifiers().getLimit() + ")");
+		}
+		return sb.toString();
+	}
+
+	/**
+	 * Obtain the {@literal Mongo Shell} json query representation.
+	 * 
+	 * @return never {@literal null}.
+	 * @since 2.2
+	 */
+	public String toJson() {
+		return toJson(JSON_WRITER_SETTINGS);
+	}
+
+	/**
+	 * Obtain the json query representation applying given {@link JsonWriterSettings settings}.
+	 *
+	 * @param settings must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 2.2
+	 */
+	public String toJson(JsonWriterSettings settings) {
+		return asDocument().toJson(settings);
 	}
 }

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/support/QuerydslRepositorySupportTests.java

@@ -25,7 +25,6 @@ import org.bson.types.ObjectId;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
-
 import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.data.annotation.Id;
@@ -39,6 +38,7 @@ import org.springframework.data.mongodb.repository.QPerson;
 import org.springframework.data.mongodb.repository.User;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.util.StringUtils;
 
 /**
  * Unit tests for {@link QuerydslRepositorySupport}.
@@ -248,6 +248,33 @@ public class QuerydslRepositorySupportTests {
 		assertThat(inQuery.fetchOne()).isEqualTo(document);
 	}
 
+	@Test // DATAMONGO-2327
+	public void toJsonShouldRenderQuery() {
+
+		QPerson p = QPerson.person;
+		SpringDataMongodbQuery<Person> query = repoSupport.from(p).where(p.lastname.eq("Matthews"))
+				.orderBy(p.firstname.asc()).offset(1).limit(5);
+
+		assertThat(StringUtils.trimAllWhitespace(query.toJson())).isEqualTo("{\"lastname\":\"Matthews\"}");
+	}
+
+	@Test // DATAMONGO-2327
+	public void toStringShouldRenderQuery() {
+
+		QPerson p = QPerson.person;
+		SpringDataMongodbQuery<Person> query = repoSupport.from(p).where(p.lastname.eq("Matthews"));
+
+		assertThat(StringUtils.trimAllWhitespace(query.toString())).isEqualTo("find({\"lastname\":\"Matthews\"})");
+
+		query = query.orderBy(p.firstname.asc());
+		assertThat(StringUtils.trimAllWhitespace(query.toString()))
+				.isEqualTo("find({\"lastname\":\"Matthews\"}).sort({\"firstname\":1})");
+
+		query = query.offset(1).limit(5);
+		assertThat(StringUtils.trimAllWhitespace(query.toString()))
+				.isEqualTo("find({\"lastname\":\"Matthews\"}).sort({\"firstname\":1}).skip(1).limit(5)");
+	}
+
 	@Data
 	@Document
 	public static class Outer {