Spring Boot Query DSL Filters with MongoDB

1.Overview

Querydsl is a framework that helps to write type-safe SQL-like queries for any database. Pretty much like a proxy layer to the database layer.

2 Setup

Add dependency

<dependencies>
<dependency>
 <groupId>com.querydsl</groupId>
 <artifactId>querydsl-apt</artifactId>
 <version>${querydsl.version}</version>
 <scope>provided</scope>
 </dependency>
<dependency>
 <groupId>com.querydsl</groupId>
 <artifactId>querydsl-jpa</artifactId>
 <version>${querydsl.version}</version>
 </dependency>
</dependencies>

To Generate Q-Classes

<plugins>
    <plugin>
        <groupId>com.mysema.maven</groupId>
        <artifactId>apt-maven-plugin</artifactId>
        <version>1.1.3</version>
        <executions>
            <execution>
                <goals>
                    <goal>process</goal>
                </goals>
                <configuration>
                    <outputDirectory>target/generated-sources/java</outputDirectory>
                    <processor>
                        org.springframework.data.mongodb.repository.support.MongoAnnotationProcessor
                    </processor>
                </configuration>
            </execution>
        </executions>
    </plugin>
</plugins>

Run maven goal mvn clean install

Will generate new classes under target/generated-sources/java/{your package structure}

3. QueryDslPredicateExecutor & QuerydslBinderCustomizer

Enable Querydsl in our User repository using QueryDslPredicateExecutor

@Repository
public interface UserRepository extends BaseRepository<User>,  QuerydslPredicateExecutor<User> {

}

Now to filter create a predicate under folder “repository → predicate → UserPredicate.java”

public class UserPredicate implements  QuerydslBinderCustomizer<QUser> {
    
@Override
public void customize(QuerydslBindings querydslBindings, 
                      QUser qUser) {
       // your queries will go here
    }
}

4. Queries with DSL

Following imports can help to build the query

import com.querydsl.core.types.dsl.BooleanExpression;
import com.querydsl.core.types.dsl.EnumExpression;
import com.querydsl.core.types.dsl.StringExpression;

4.1 Eq operator

querydslBindings
.bind(qUser.active)
.as("active")
.first(BooleanExpression::eq); 
// we are using boolean expression because `active` field type is boolean

4.2 String operator

querydslBindings.bind(qUser.fullName)
.as("name")
.first(StringExpression::eq);
// we are using boolean expression because `fullName` field type is string

4.3 Enum operator

querydslBindings.bind(qUser.type)
.as("type")
.first(EnumExpression::eq);
// we are using boolean expression because `type` field type is ENUM

4.4 In Array Operator (match-any)

querydslBindings.bind(qUser.cities)
.as("city-id")
.first((path, integers) -> path.any().in(integers));

4.5 Greater or Lesser operator

querydslBindings.bind(qUser.registerDate)
.as("register-date")
.first((path, value) -> path.goe(value));
or 
bindings.bind(qUser.registerDate)
.as("register-date")
.first((path, value) -> path.loe(value));

4.6 StartingWith and EndingWith

querydslBindings.bind(qUser.fullName)
.as("name")
.first((path, value) -> path.startsWith("Irfan"));

4.7 Between

querydslBindings.bind(qUser.createdAt)
.as("created-at")
.all((path, values) -> {
    Iterator<? extends LocalDateTime> it = values.stream().sorted().iterator();
    LocalDateTime from = it.next();
    if (values.size() >= 2) {
        LocalDateTime to = it.next();
        return Optional.of(path.between(from, to));
    } else {
        return Optional.of(path.goe(from));
    }
});

4.8 Transient Fields

This is used when you have a different type or format of the field than specified in the entity. For example if createAt is date-time field but you want to filter only by date without sending time in the query or in the URL. We can achieve this using the below method

Goto respective entity class in our case it is User

com/irfanbaigse/repository/entity/User.java and add folowing

// this fields will not be saved in db
@Transient
@Getter(value = AccessLevel.PRIVATE)
@DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME)
private LocalDate creationDateTo;
@Transient
@Getter(value = AccessLevel.PRIVATE)
@DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME)
private LocalDate creationDateFrom;

Then use it in predicate like this

// date field
querydslBindings.bind(qUser.creationDateFrom)
        .as("created-from")
        .first((path, value) -> qUser.createdAt.goe(value.atStartOfDay()));
querydslBindings.bind(qUser.creationDateTo)
        .as("created-to")
        .first((path, value) ->qUser.createdAt.loe(value.atTime(LocalTime.MAX))); 
// end of the day

sample code can be found here on Github.

Reference

• http://www.querydsl.com
• https://www.baeldung.com/queries-in-spring-data-mongodb