Spring Boot Modelmapper - StackOverflowError：null

Question

Im getting 1) Error mapping entity.Team to TeamDTO followed by java.lang.StackOverflowError: null without any really cause or line in the stacktrace. Im trying to fetch an entity from database by Id.

Entity:

@Entity
@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public class Team implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String teamName;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "fk_league", referencedColumnName = "id", nullable = false)
    private League league;

    @OneToMany(mappedBy="homeTeam")
    List<Match> homeTeamMatches = new ArrayList<>();

    @OneToMany(mappedBy="awayTeam")
    List<Match> awayTeamMatches = new ArrayList<>();

    @Column(name = "created_at", nullable = false, updatable = false)
    private Date createdAt;

    @Column(name = "updated_at", nullable = false)
    private Date updatedAt;

    public Team(String teamName, League league) {
        this.teamName = teamName;
        this.league = league;
    }

    @PrePersist
    private void createdAt() {
        this.createdAt = new Date();
        this.updatedAt = new Date();
    }

    @PreUpdate
    private void updatedAt() {
        this.updatedAt = new Date();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Team team = (Team) o;
        return id.equals(team.id) &&
                teamName.equals(team.teamName);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, teamName);
    }
}

DTO for the Entity:

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonIgnoreProperties({"homeTeamMatches", "awayTeamMatches", "league"})
public class TeamDTO {
    private Long id;

    private String teamName;

    private LeagueDTO league;

    List<MatchDTO> homeTeamMatches = new ArrayList<>();

    List<MatchDTO> awayTeamMatches = new ArrayList<>();

    private Date createdAt;

    private Date updatedAt;
}

Here Im fetching the data and converting to DTO to return it back to the controller:

private final TeamRepository teamRepository;
private final ModelMapper modelMapper = new ModelMapper();

public TeamService(@Autowired TeamRepository teamRepository) {
    this.teamRepository = teamRepository;
}

public TeamDTO findById(Long id) {
    return convertToCategoryDTO(teamRepository.findById(id).get());
}

private TeamDTO convertToCategoryDTO(Team team) {
    modelMapper.getConfiguration()
            .setMatchingStrategy(MatchingStrategies.LOOSE);
    return modelMapper
            .map(team, TeamDTO.class);
}

So can anyone help me??

EDIT: Found out that this two lines in my TeamDTO causes the stackoverflow:

List<MatchDTO> homeTeamMatches = new ArrayList<>();

List<MatchDTO> awayTeamMatches = new ArrayList<>();

How to map these properties two without causing an stackoverflow?

Answer 1

The private final ModelMapper modelMapper = new ModelMapper(); is not a good practice in Spring context.

you need to create a separate config class as below,

@Configuration
public class AppConfiguration {

    @Bean
    public ModelMapper modelMapper(){
        return new ModelMapper();
    }

}

and use

@Autowired
private final ModelMapper modelMapper;

or in setter injection.