Querying MongoDB

This chapter describes the querying functionality of the MongoDB module.

Maven Integration

Add the following dependencies to your Maven project:

<dependency>
  <groupId>io.github.openfeign.querydsl</groupId>
  <artifactId>querydsl-mongodb</artifactId>
  <version>7.1</version>
</dependency>

Configure the maven-compiler-plugin to run the Querydsl annotation processor:

<plugin>
  <artifactId>maven-compiler-plugin</artifactId>
  <configuration>
    <generatedSourcesDirectory>target/generated-sources/java</generatedSourcesDirectory>
  </configuration>
  <dependencies>
    <dependency>
      <groupId>io.github.openfeign.querydsl</groupId>
      <artifactId>querydsl-apt</artifactId>
      <version>7.1</version>
      <classifier>morphia</classifier>
    </dependency>
  </dependencies>
</plugin>

The MorphiaAnnotationProcessor finds domain types annotated with com.google.code.morphia.annotations.Entity and generates Querydsl query types for them.

Run mvn clean install and your query types will be generated into target/generated-sources/java.

Querying

Querying with Querydsl MongoDB with Morphia:

Morphia morphia;
Datastore datastore;
// ...
QUser user = new QUser("user");
MorphiaQuery<User> query = new MorphiaQuery<User>(morphia, datastore, user);
List<User> list = query
    .where(user.firstName.eq("Bob"))
    .fetch();

General Usage

Use the cascading methods of the MongodbQuery class:

• where: Add query filters, either in varargs form separated via commas or cascaded via the and operator. Supported operations are operations performed on PStrings except matches, indexOf, and charAt.
• orderBy: Add ordering of the result as a varargs array of order expressions. Use asc() and desc() on numeric, string, and other comparable expressions to access OrderSpecifier instances.
• limit, offset, restrict: Set the paging of the result. limit for max results, offset for skipping rows, and restrict for defining both in one call.

Ordering

query
    .where(doc.title.like("*"))
    .orderBy(doc.title.asc(), doc.year.desc())
    .fetch();

The results are sorted ascending based on title and descending based on year.

Limit

query
    .where(doc.title.like("*"))
    .limit(10)
    .fetch();

Offset

query
    .where(doc.title.like("*"))
    .offset(3)
    .fetch();

Geospatial Queries

Support for geospatial queries is available for Double typed arrays (Double[]) via the near method:

query
    .where(geoEntity.location.near(50.0, 50.0))
    .fetch();

Select Only Relevant Fields

To select only relevant fields, use the overloaded projection methods fetch, iterate, fetchOne, and fetchFirst:

query
    .where(doc.title.like("*"))
    .fetch(doc.title, doc.path);

This query loads only the title and path fields of the documents.