Cassandra - Lab 4

In this lab, we will learn how to UDT.

1. Define the `Director` Entity

Steps

Create a class called Director in the expert.os.labs.persistence package
Define the class with the @Entity annotation
```
@Entity
public class Director {
```
Add the fields as specified in the provided code adding the@Column annotations for all
```
@Column
private String name;

@Column
private Set<String> movies;
```
Implement constructors, setter methods, equals, hashCode, and toString method.

Expected results

Entity Director created

Solution

Click to see...

import jakarta.nosql.Column;
import jakarta.nosql.Entity;

import java.util.Set;

@Entity
public class Director {

    @Column
    private String name;

    @Column
    private Set<String> movies;

    public Director() {
    }

    public Director(String name, Set<String> movies) {
        this.name = name;
        this.movies = movies;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setMovies(Set<String> movies) {
        this.movies = movies;
    }

    @Override
    public String toString() {
        return "Director{" +
            "name='" + name + '\'' +
            ", movies=" + movies +
            '}';
    }
}

2. Implement the Builder class

Steps

Create a class called DirectorBuilder in the expert.os.labs.persistence package
Add the same fields we had previously added to the Director class, without the annotations
- note that we need to initialize the movies attribute
```
private String name;
private final Set<String> movies = new HashSet<>();
```
Add the builder methods for each field
- for the movies field, add a single movie to the Set
Add the build() method creating a new instance of Director using its constructor
In the Director class add the builder method referring to the DirectorBuilder

Expected results

Builder class DirectorBuilder created

Solution

Click to see...

import java.util.Set;

public class DirectorBuilder {

    private String name;
    private Set<String> movies;

    public DirectorBuilder name(String name) {
        this.name = name;
        return this;
    }

    public DirectorBuilder addMovie(String movie) {
        this.movies.add(movie)
        return this;
    }

    public Director build() {
        return new Director(name, movies);
    }
}

3. Define the `Movie` Entity

Steps

Create a class called Movie in the expert.os.labs.persistence package
Define the class with the @Entity annotation
Define instance variables for name, age, and director, where the name is the ID and must have the @Id annotation and the other attributes the @Column annotation
```
@Id("name")
private String name;

@Column
private Integer age;

@Column
private Director director;
```
Annotate the director field with @UDT("director") from the package org.eclipse.jnosql.databases.cassandra.mapping to specify that it's a User-Defined Type (UDT) with the name "director"
```
@Column
UDT("director")
private Director director;
```
Implement the constructor, getter, setters, equals, hashCode, and toString methods for the class

Expected results

Entity Director created

Solution

Click to see...

import jakarta.nosql.Column;
import jakarta.nosql.Entity;
import jakarta.nosql.Id;
import org.eclipse.jnosql.databases.cassandra.mapping.UDT;

@Entity
public class Movie {

    @Id("name")
    private String name;

    @Column
    private Integer age;

    @Column
    @UDT("director")
    private Director director;

    public Movie(String name, Integer age, Director director) {
        this.name = name;
        this.age = age;
        this.director = director;
    }

    // getters and setters ignored

    @Override
    public String toString() {
        return "Movie{" +
            "name='" + name + '\'' +
            ", age=" + age +
            ", director=" + director +
            '}';
    }
}

4. Define the `Movie` Repository

Steps

Create an interface called MovieRepository in the expert.os.labs.persistence package
Annotate the interface with @Repository using the package from jakarta.data.repository to indicate it's a Jakarta Data repository
Extend the CassandraRepository interface from the package org.eclipse.jnosql.databases.cassandra.mapping and specify the entity type (Movie) and the ID type (String) as type parameters
```
@Repository
public interface MovieRepository extends CassandraRepository<Movie, String> {
}
```
Define the custom query findByAge()
```
List<Movie> findByAge(Integer age);
```
Define a custom query findAllQuery() adding the @CQL annotation from the package org.eclipse.jnosql.databases.cassandra.mapping where its parameter have the following query select * from developers.Movie
```
@CQL("select * from developers.Movie")
List<Movie> findAllQuery();
```

Expected results

Repository MovieRepository containing two custom queries

Solution

Click to see...

import jakarta.data.repository.Repository;
import org.eclipse.jnosql.databases.cassandra.mapping.CQL;
import org.eclipse.jnosql.databases.cassandra.mapping.CassandraRepository;

import java.util.List;

@Repository
public interface MovieRepository extends CassandraRepository<Movie, String> {

    List<Movie> findByAge(Integer age);

    @CQL("select * from developers.Movie")
    List<Movie> findAllQuery();
}

5. Create the execution class for Cassandra UDT

Steps

Create a class called AppCassandraUDT in the expert.os.labs.persistence package

Add a main method

public static void main(String[] args) {
}

Set up a try-with-resources block, inside the main method, to manage the Jakarta EE SeContainer that is responsible for dependency injection and managing resources
```
try (SeContainer container = SeContainerInitializer.newInstance().initialize()) {     
}
```
Obtain an instance of the MovieRepository interface using Jakarta EE's SeContainer. It is done by selecting and getting an instance of the repository
```
MovieRepository repository = container.select(MovieRepository.class).get();
```

Add the following Movie instances with its data

Movie matrix = new Movie();
matrix.setName("The Matrix");
matrix.setAge(1999);
matrix.setDirector(Director.builder().name("Lana Wachowski")
    .add("The Matrix").add("The Matrix Reloaded").add("Assassins").build());

Movie fightClub = new Movie();
fightClub.setName("Fight Club");
fightClub.setAge(1999);
fightClub.setDirector(Director.builder().name("David Fincher")
    .add("Fight Club").add("Seven").add("The Social Network").build());

Movie americanBeauty = new Movie();
americanBeauty.setName("American Beauty");
americanBeauty.setAge(1999);
americanBeauty.setDirector(Director.builder().name("Sam Mendes")
    .add("Spectre").add("SkyFall").add("American Beauty").build());

Use the repository to save all the created Movie, as a List of entities to Cassandra using repository.saveAll()
```
repository.saveAll(List.of(matrix, fightClub, americanBeauty));
```

Retrieve and print all movies using repository.findAllQuery()

List<Movie> allMovies = repository.findAllQuery();
System.out.println("All movies = " + allMovies);

Retrieve and print movies from the year 1999 using repository.findByAge(1999)

List<Movie> movieByAge = repository.findByAge(1999);
System.out.println("Movies from 1999 = " + movieByAge);

Define a private constructor for the AppCassandraUDT class to prevent instantiation since it contains only static methods:
```
private AppCassandraUDT() {
}
```
Run the main() method

Expected results

The following output

All movies = [Movie{name='Fight Club', age=1999, director=Director{name='David Fincher', movies=[Fight Club, Seven, The Social Network]}}, Movie{name='American Beauty', age=1999, director=Director{name='Sam Mendes', movies=[American Beauty, SkyFall, Spectre]}}, Movie{name='The Matrix', age=1999, director=Director{name='Lana Wachowski', movies=[The Matrix, Assassins, The Matrix Reloaded]}}]

Movies from 1999 = [Movie{name='Fight Club', age=1999, director=Director{name='David Fincher', movies=[Fight Club, Seven, The Social Network]}}, Movie{name='American Beauty', age=1999, director=Director{name='Sam Mendes', movies=[American Beauty, SkyFall, Spectre]}}, Movie{name='The Matrix', age=1999, director=Director{name='Lana Wachowski', movies=[The Matrix, Assassins, The Matrix Reloaded]}}]

Solution

Click to see...

import jakarta.enterprise.inject.se.SeContainer;
import jakarta.enterprise.inject.se.SeContainerInitializer;

import java.util.List;

public class AppCassandraUDT {

    public static void main(String[] args) {
        try (SeContainer container = SeContainerInitializer.newInstance().initialize()) {
            MovieRepository repository = container.select(MovieRepository.class).get();

            Movie matrix = new Movie();
            matrix.setName("The Matrix");
            matrix.setAge(1999);
            matrix.setDirector(Director.builder().name("Lana Wachowski")
                .addMovie("The Matrix").addMovie("The Matrix Reloaded").addMovie("Assassins").build());

            Movie fightClub = new Movie();
            fightClub.setName("Fight Club");
            fightClub.setAge(1999);
            fightClub.setDirector(Director.builder().name("David Fincher")
                .addMovie("Fight Club").add("Seven").addMovie("The Social Network").build());

            Movie americanBeauty = new Movie();
            americanBeauty.setName("American Beauty");
            americanBeauty.setAge(1999);
            americanBeauty.setDirector(Director.builder().name("Sam Mendes")
                .addMovie("Spectre").addMovie("SkyFall").addMovie("American Beauty").build());

            repository.saveAll(List.of(matrix, fightClub, americanBeauty));

            List<Movie> allMovies = repository.findAllQuery();
            System.out.println("All movies = " + allMovies);

            List<Movie> movieByAge = repository.findByAge(1999);
            System.out.println("Movies from 1999 = " + movieByAge);
        }
    }

    public AppCassandraUDT() {
    }
}

Cassandra - Lab 4

1. Define the Director Entity

Steps

Expected results

Solution

2. Implement the Builder class

Steps

Expected results

Solution

3. Define the Movie Entity

Steps

Expected results

Solution

4. Define the Movie Repository

Steps

Expected results

Solution

5. Create the execution class for Cassandra UDT

Steps

Expected results

Solution

1. Define the `Director` Entity

3. Define the `Movie` Entity

4. Define the `Movie` Repository