Fetch.Azy keeps loading the attribute what can it be?

Question

Even if I use Azy my list is loaded, someone knows what’s going on?

public class Departamento {
      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      private Long id;
      @NotEmpty(message="O campo descrição é obrigatório")
      private String descricao;
     
      @JsonProperty(access = Access.WRITE_ONLY)
      @OneToMany(fetch = FetchType.LAZY)
      @JoinColumn(name= "subordinador")
      private List<Departamento> subordinados;
        
}


//getter e setters

Answer 1

I performed a test with your mapping, and did not generate the reported problem.

Departmental class:

@Entity
@Data
public class Departamento {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotEmpty(message="O campo descrição é obrigatório")
    private String descricao;
    
    @JsonProperty(access = Access.WRITE_ONLY)
    @OneToMany(fetch = FetchType.LAZY)
    @JoinColumn(name= "subordinador")
    private List<Departamento> subordinados;
}

I created a repository to make a test query:

public interface DepartamentoRepository extends JpaRepository<Departamento, Long> {
    
}

I created a class to run on Spring Startup:

@Component
@Data
@AllArgsConstructor
public class Inicializacao {
    
    DepartamentoRepository repository;

    @EventListener(ApplicationReadyEvent.class)
    public void doSomethingAfterStartup() {
    
        this.salvarDepartamentos();
        this.recuperarDepartamentos();
    }
    
    public void salvarDepartamentos() {

        Departamento fiscal = new Departamento();
        fiscal.setDescricao("fiscal");
        repository.save(fiscal);
        
        Departamento almoxarifado = new Departamento();
        almoxarifado.setDescricao("almoxarifado");
        repository.save(almoxarifado);
        
        Departamento administracao = new Departamento();
        administracao.setDescricao("administracao");
        administracao.setSubordinados(Arrays.asList(fiscal, almoxarifado));
        repository.save(administracao);
    }

    public void recuperarDepartamentos() {
        Optional<Departamento> retorno = repository.findById(3L);
        Departamento departamento = retorno.get();
        System.out.println(departamento.getSubordinados());
    }
}

The call in the code department.getSubordinated() generates exactly the expected error of Lazy:

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.demo.model.Departamento.subordinados, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:606) ~[hibernate-core-5.4.30.Final.jar:5.4.30.Final]
AbstractPersistentCollection.java:606
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:218) ~[hibernate-core-5.4.30.Final.jar:5.4.30.Final]
AbstractPersistentCollection.java:218
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.30.Final.jar:5.4.30.Final]
AbstractPersistentCollection.java:585
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.30.Final.jar:5.4.30.Final]
AbstractPersistentCollection.java:149
    at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:621) ~[hibernate-core-5.4.30.Final.jar:5.4.30.Final]
PersistentBag.java:621
    at java.base/java.lang.String.valueOf(String.java:3388) ~[na:na]
String.java:3388
    at java.base/java.io.PrintStream.println(PrintStream.java:1047) ~[na:na]
PrintStream.java:1047
    at com.example.demo.model.Inicializacao.recuperarDepartamentos(Inicializacao.java:46) ~[classes/:na]
Inicializacao.java:46

That is, the data is not being loaded, because by default Onetomany = LAZY. In its mapping was still explicit.

The specification contained in JSR-000317 informs that by default:

OneToMany: LAZY
ManyToOne: EAGER
ManyToMany: LAZY
OneToOne: EAGER

Only one select was generated in the log (also expected):

2021-05-19 08:57:07.287  INFO 43976 --- [  restartedMain] .ConditionEvaluationDeltaLoggingListener : Condition evaluation unchanged
Hibernate: select departamen0_.id as id1_0_0_, departamen0_.descricao as descrica2_0_0_ from departamento departamen0_ where departamen0_.id=?

Pom used in demo project:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>11</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-rest</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
    

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>