This is a continuation of my previous question posted

I have a Student object marked as a entity, this student object is a value called assignments which is a Map<Integer, AssignmentList> assignments the AssignmentList is a custom data object for storing the list of assignments among other data associated with that list. the AssignmentList is not an annotated with a @entity or @data (code below). however in the object a list assignments are stored these assignments objects are marked as @Entity. Right now i’m still trying to figure out how to properly use the attribute converter so I will also include snippets of my Teacher and Student objects as well as other variatrions of converters i’ve tried.

Entity objects

@Entity
@Table(name = "teachers")
@Data
@EqualsAndHashCode
@ToString
@Getter
@Setter
public class Teacher implements UserDetails {
// other values
    @ElementCollection
    @Convert(converter = StudentListMapConverter.class)
    @MapKeyColumn(name = "period")
    private Map<Integer, List<Student>> students;
}

@Entity
@Table(name="students")
@Data
@EqualsAndHashCode
@ToString
@Getter
@Setter
public class Student implements UserDetails {
  // other values
    @ElementCollection
    @CollectionTable(name = "course_assignment_list", joinColumns = @JoinColumn(name = "course_id"))
    @MapKeyColumn(name = "period")
    @Column(name = "assignment_list", columnDefinition = "TEXT")
    @Convert(converter = AssignmentListConverter.class)
    private Map<Integer, AssignmentList> assignments;
  // custom constructors
}

@Entity
@Table(name = "assignments")
@Data
@EqualsAndHashCode
@ToString
@Getter
@Setter
@NoArgsConstructor
public class Assignment {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "assignment_id")
    private Long id;
    private String name;
    private Double grade;
    private boolean completed;
    private boolean overdue;
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd")
    private LocalDate dueDate;
    private String assignmentType;

AssignmentList object

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class AssignmentList {
    String subject;
    double averageGrade;
    List<Assignment> assignments;
}

Converters

I’ll put the most recent convert I’ve tried first followed by the rest.

@Converter
public class AssignmentListConverter implements AttributeConverter<AssignmentList, String> {

    private final ObjectMapper objectMapper = new ObjectMapper().registerModule(new JavaTimeModule());

    @Override
    public String convertToDatabaseColumn(AssignmentList assignmentList) {
        try {
            return objectMapper.writeValueAsString(assignmentList);
        } catch (JsonProcessingException e) {
            throw new IllegalArgumentException("Error converting AssignmentList to JSON", e);
        }
    }

    @Override
    public AssignmentList convertToEntityAttribute(String dbData) {
        try {
            return objectMapper.readValue(dbData, AssignmentList.class);
        } catch (JsonProcessingException e) {
            throw new IllegalArgumentException("Error converting JSON to AssignmentList", e);
        }
    }
}

@Converter
public class StudentListMapConverter implements AttributeConverter<Map<Integer, List<Student>>, String> {

    private static final ObjectMapper objectMapper = new ObjectMapper().registerModule(new JavaTimeModule());
    private static final TypeFactory typeFactory = objectMapper.getTypeFactory();

    @Override
    public String convertToDatabaseColumn(Map<Integer, List<Student>> attribute) {
        try {
            return objectMapper.writeValueAsString(attribute);
        } catch (JsonProcessingException e) {
            throw new IllegalArgumentException("Error converting Map<Integer, List<Student>> to JSON", e);
        }
    }

    @Override
    public Map<Integer, List<Student>> convertToEntityAttribute(String dbData) {
        try {
            return objectMapper.readValue(dbData, typeFactory.constructMapType(Map.class, typeFactory.constructType(Integer.class), typeFactory.constructCollectionType(List.class, Student.class)));
        } catch (IOException e) {
            throw new IllegalArgumentException("Error converting JSON to Map<Integer, List<Student>>", e);
        }
    }
}

Here are the other variations I tried.

@Converter
public class AssignmentListMapConverter implements AttributeConverter<Map<Integer, AssignmentList>, String> {

    private static final ObjectMapper objectMapper = new ObjectMapper()
            .registerModule(new JavaTimeModule());
    private static final TypeFactory typeFactory = objectMapper.getTypeFactory();

    @Override
    public String convertToDatabaseColumn(Map<Integer, AssignmentList> attribute) {
        try {
            return objectMapper.writeValueAsString(attribute);
        } catch (JsonProcessingException e) {
            throw new IllegalArgumentException("Error converting Map<Integer, AssignmentList> to JSON", e);
        }
    }

    @Override
    public Map<Integer, AssignmentList> convertToEntityAttribute(String dbData) {
        try {
            return objectMapper.readValue(dbData, typeFactory.constructMapType(Map.class,
                    typeFactory.constructType(Integer.class),
                    typeFactory.constructType(AssignmentList.class)));
        } catch (IOException e) {
            throw new IllegalArgumentException("Error converting JSON to Map<Integer, AssignmentList>", e);
        }
    }
}

@Converter
public class AssignmentConverter implements AttributeConverter<Object, String> {

    private static final ObjectMapper objectMapper = new ObjectMapper()
            .registerModule(new JavaTimeModule());
    private static final TypeFactory typeFactory = objectMapper.getTypeFactory();

    @Override
    public String convertToDatabaseColumn(Object attribute) {
        try {
            return objectMapper.writeValueAsString(attribute);
        } catch (JsonProcessingException e) {
            throw new IllegalArgumentException("Error converting object to JSON", e);
        }
    }

    @Override
    public Object convertToEntityAttribute(String dbData) {
        if (dbData.startsWith("{")) {
            try {
                return objectMapper.readValue(dbData, typeFactory
                        .constructMapType(Map.class,
                        typeFactory.constructType(Integer.class),
                        typeFactory.constructType(AssignmentList.class)));
            } catch (IOException e) {
                throw new IllegalArgumentException("Error converting JSON to Map<Integer, AssignmentList>", e);
            }
        } else {
            try {
                return objectMapper.readValue(dbData, AssignmentList.class);
            } catch (JsonProcessingException e) {
                throw new IllegalArgumentException("Error converting JSON to AssignmentList", e);
            }
        }
    }
}

Errors

using the most recent build I get these logs when loading the command line runner method which creates a very basic Teacher, student, and Assignment object for testing:

java.lang.IllegalStateException: Failed to execute CommandLineRunner
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:772) ~[spring-boot-3.0.4.jar:3.0.4]
at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:753) ~[spring-boot-3.0.4.jar:3.0.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:317) ~[spring-boot-3.0.4.jar:3.0.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1304) ~[spring-boot-3.0.4.jar:3.0.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1293) ~[spring-boot-3.0.4.jar:3.0.4]
at com.tracer.StudentTrackerApiApplication.main(StudentTrackerApiApplication.java:29) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-3.0.4.jar:3.0.4]
Caused by: org.springframework.transaction.TransactionSystemException: Could not commit JPA transaction
at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:570) ~[spring-orm-6.0.6.jar:6.0.6]
at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:743) ~[spring-tx-6.0.6.jar:6.0.6]
at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:711) ~[spring-tx-6.0.6.jar:6.0.6]
at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:659) ~[spring-tx-6.0.6.jar:6.0.6]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:409) ~[spring-tx-6.0.6.jar:6.0.6]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-6.0.6.jar:6.0.6]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.6.jar:6.0.6]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) ~[spring-tx-6.0.6.jar:6.0.6]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.6.jar:6.0.6]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:163) ~[spring-data-jpa-3.0.3.jar:3.0.3]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.6.jar:6.0.6]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) ~[spring-aop-6.0.6.jar:6.0.6]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.6.jar:6.0.6]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:218) ~[spring-aop-6.0.6.jar:6.0.6]
at jdk.proxy4/jdk.proxy4.$Proxy150.save(Unknown Source) ~[na:na]
at com.tracer.StudentTrackerApiApplication.lambda$run$0(StudentTrackerApiApplication.java:72) ~[classes/:na]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:769) ~[spring-boot-3.0.4.jar:3.0.4]
… 10 common frames omitted
Caused by: jakarta.persistence.RollbackException: Error while committing the transaction
at org.hibernate.internal.ExceptionConverterImpl.convertCommitException(ExceptionConverterImpl.java:83) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:104) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:561) ~[spring-orm-6.0.6.jar:6.0.6]
… 26 common frames omitted
Caused by: java.lang.UnsupportedOperationException: null
at org.hibernate.type.descriptor.java.spi.CollectionJavaType.unwrap(CollectionJavaType.java:82) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.type.descriptor.java.spi.BasicCollectionJavaType.unwrap(BasicCollectionJavaType.java:333) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.type.descriptor.java.spi.BasicCollectionJavaType.unwrap(BasicCollectionJavaType.java:48) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.type.descriptor.jdbc.ArrayJdbcType$2.getArray(ArrayJdbcType.java:176) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.type.descriptor.jdbc.ArrayJdbcType$2.doBind(ArrayJdbcType.java:122) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.type.descriptor.jdbc.BasicBinder.bind(BasicBinder.java:63) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.type.AbstractStandardBasicType.nullSafeSet(AbstractStandardBasicType.java:221) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.type.AbstractStandardBasicType.nullSafeSet(AbstractStandardBasicType.java:217) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.type.AbstractSingleColumnStandardBasicType.nullSafeSet(AbstractSingleColumnStandardBasicType.java:34) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.persister.collection.AbstractCollectionPersister.writeElement(AbstractCollectionPersister.java:1010) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.persister.collection.AbstractCollectionPersister.recreate(AbstractCollectionPersister.java:1473) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.action.internal.CollectionRecreateAction.execute(CollectionRecreateAction.java:47) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:612) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.engine.spi.ActionQueue.lambda$executeActions$1(ActionQueue.java:483) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at java.base/java.util.LinkedHashMap.forEach(LinkedHashMap.java:721) ~[na:na]
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:480) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:329) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:39) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:107) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1425) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:477) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:2234) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:1930) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:439) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:183) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:281) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:101) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]
… 27 common frames omitted

when messing around with the data loader I’ve found that when I don’t set the Student List in Teacher to the created students or assignment objects. or when i comment out the creation of the student and Assignment objects I don’t get any error when booting up the application. But thats all I’ve really managed to deduce.