JPA filter query builder for JSON-QL. Allows to apply filters with JPA-supported persistence technology like Hibernate.

To use this library please add it as your gradle/maven dependency with these remarks:

dependencies {
    implementation 'com.lifeinide.jsonql:jsonql-jpa:VERSION'
}

The following example uses Hibernate persistence technology with JPA and H2 database.

Note, you can check the full working example in tests.

{
dependencies {
    implementation group: 'com.lifeinide.jsonql', name: 'jsonql-jpa', version: '1.0.2'
    implementation group: 'org.hibernate', name: 'hibernate-core', version: '5.4.9.Final'
    implementation group: 'com.h2database', name: 'h2', version: '1.4.199'
}

@Entity
public class User {

    @Id private Long id;
    protected String username;
    protected boolean admin = false;

    // getters and setters go here

}

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
			 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
			 xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
			 version="2.0">
	<persistence-unit name="my-unit-name">
		<class>User</class>
		<exclude-unlisted-classes>true</exclude-unlisted-classes>
		<properties>
			<property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
			<property name="hibernate.hbm2ddl.auto" value="update"/>
			<property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
			<property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:test;DB_CLOSE_DELAY=-1"/>
		</properties>
	</persistence-unit>
</persistence>

The frame below supports paging and sorting automatically, we just need to add custom filtering fields. We want to make possible to display existing users and filter them using admin flag:

public class UserFilter extends DefaultPageableRequest {

    protected SingleValueQueryFilter<Boolean> admin;

    // getters and setters go here

}

Then you just need to expose UserFilter frame in your endpoint. We don't enforce any request-handling technology and this library can be used with any JSON or GraphQL based framework. Here is a simple hyphothetical controller that could be used to list users:

@Controller("/user")
public class UserController {

    @Post("/list")
    public Page<User> listUsers(UserFilter filter) {
        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("my-unit-name");
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        entityManager.getTransaction().begin();

        try {
            return new DefaultJpaFilterQueryBuilder<User>(em, User.class)
                .add("admin", filter.getAdmin())
                .list(filter);
        } finally {
            entityManager.getTransaction().commit();
            entityManager.close();
        }
    }   

}

Of course, this is only a clunky example. Usually the EntityManager will be obtained elsewhere, and it's the only thing required to build JpaFilterQueryBuilder.

Now, you can test the controller sending following JSON-s to listUsers() endpoint:

To just get all users unpaginated:

{}

To get all users paginated:

{
  "pageSize": 20,
  "page": 1
}

To get all users paginated and sorted by name:

{
  "pageSize": 20,
  "page": 1,
  "sort": [{
    "field": "username",
    "direction": "ASC"        
  }]
}

To get only admins paginated and sorted by name:

{
  "pageSize": 20,
  "page": 1,
  "sort": [{
    "field": "username",
    "direction": "ASC"        
  }],
  "admin": {
    "condition": "eq",
    "value": true  
  } 
}

And of course you can add a lot more fields to your User entity and then consider them in UserFilter. Besides SingleValueQueryFilter, which just filters out a single primitive value like Boolean or Enum, there're plenty of other predefined filters available and described here.