Objectbox-java: Cannot convert List<> of custom class to String in Objectbox

[cincospenguinos]

Hey guys, I love your project! I'm having trouble getting this to work though. I can't seem to figure out what I'm doing wrong, which is making me wonder if it's a bug.

Issue Basics

• Using the latest version 1.5.0
• This occurs every time I attempt to build my project

Reproducing the bug

I have a custom entity class that has two lists of another custom class. I defined a converter for each of those lists to convert the list into a JSON string using Gson. When I attempt to build the project, I'm given the error message Cause: cannot find constructor io.objectbox.relation.ToMany(com.stoicapps.roll4initiative.models.Encounter,io.objectbox.Property).

Code

So the class with the lists is the Encounter class:

@Entity
public class Encounter {

    @Id
    private long id;

    private String name;

    private int currentRound;

    @Convert(converter =  EncounterParticipantConverter.class, dbType = String.class)
    private List<Creature> livingParticipants;

    @Convert(converter =  EncounterParticipantConverter.class, dbType = String.class)
    private List<Creature> deadParticipants;

    private int currentTurnIndex;
    private long uniqueIdentifier;

    ...

Here's the Creature class:

@Entity
public class Creature {

    @Id
    private long id;

    @Convert(converter =  CreatureTypeConverter.class, dbType = Integer.class)
    private CreatureType type;

    @Index
    private String name;

    @Convert(converter = DiceRollConverter.class, dbType = String.class)
    private DiceRoll initiativeDiceRoll;
    private int initiativeValue;

    @Convert(converter = DiceRollConverter.class, dbType = String.class)
    private DiceRoll hitPointsDiceRoll;
    private int hitPointsValue;

Here's the converter for the lists in the Encounter class:

public static class EncounterParticipantConverter implements PropertyConverter<List<Creature>, String> {

        @Override
        public List<Creature> convertToEntityProperty(String jsonString) {
            if (jsonString == null) {
                return null;
            }

            return new Gson().fromJson(jsonString, new TypeToken<List<Creature>>(){}.getType());
        }

        @Override
        public String convertToDatabaseValue(List<Creature> creatureList) {
            if (creatureList == null) {
                return null;
            }

            return new Gson().toJson(creatureList);
        }
    }

Let me know if you need to see anything else.

Logs & stackstraces

Here's the full stack trace:

org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:objectboxTransformDebugUnitTest'.
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:100)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:70)
    at org.gradle.api.internal.tasks.execution.OutputDirectoryCreatingTaskExecuter.execute(OutputDirectoryCreatingTaskExecuter.java:51)
    at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:62)
    at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54)
    at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:60)
    at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:97)
    at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:87)
    at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.java:52)
    at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
    at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:54)
    at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
    at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:34)
    at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.run(DefaultTaskGraphExecuter.java:248)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)
    at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:241)
    at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:230)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.processTask(DefaultTaskPlanExecutor.java:123)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.access$200(DefaultTaskPlanExecutor.java:79)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:104)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:98)
    at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.execute(DefaultTaskExecutionPlan.java:626)
    at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.executeWithTask(DefaultTaskExecutionPlan.java:581)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.run(DefaultTaskPlanExecutor.java:98)
    at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
    at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
    at java.lang.Thread.run(Thread.java:745)
Caused by: io.objectbox.gradle.transform.TransformException: Could not transform class "com.stoicapps.roll4initiative.models.Encounter" (Could not insert init code for field livingParticipants in constructor)
    at io.objectbox.gradle.transform.ClassTransformer.transformEntityAndBases(ClassTransformer.kt:146)
    at io.objectbox.gradle.transform.ClassTransformer.transformEntities(ClassTransformer.kt:117)
    at io.objectbox.gradle.transform.ClassTransformer.transformOrCopyClasses(ClassTransformer.kt:95)
    at io.objectbox.gradle.transform.ObjectBoxJavaTransform.transform(ObjectBoxJavaTransform.kt:47)
    at io.objectbox.gradle.transform.ObjectBoxAndroidTransform$Registration$injectTransformTask$1.execute(ObjectBoxAndroidTransform.kt:131)
    at io.objectbox.gradle.transform.ObjectBoxAndroidTransform$Registration$injectTransformTask$1.execute(ObjectBoxAndroidTransform.kt:52)
    at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:780)
    at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:747)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$1.run(ExecuteActionsTaskExecuter.java:121)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:110)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:92)
    ... 32 more
Caused by: io.objectbox.gradle.transform.TransformException: Could not insert init code for field livingParticipants in constructor
    at io.objectbox.gradle.transform.ClassTransformer.transformConstructors(ClassTransformer.kt:281)
    at io.objectbox.gradle.transform.ClassTransformer.transformEntity(ClassTransformer.kt:186)
    at io.objectbox.gradle.transform.ClassTransformer.transformEntityAndBases(ClassTransformer.kt:142)
    ... 46 more
Caused by: javassist.CannotCompileException: [source error] cannot find constructor io.objectbox.relation.ToMany(com.stoicapps.roll4initiative.models.Encounter,io.objectbox.Property)
    at javassist.CtConstructor.insertBeforeBody(CtConstructor.java:273)
    at io.objectbox.gradle.transform.ClassTransformer.transformConstructors(ClassTransformer.kt:279)
    ... 48 more
Caused by: compile error: cannot find constructor io.objectbox.relation.ToMany(com.stoicapps.roll4initiative.models.Encounter,io.objectbox.Property)
    at javassist.compiler.TypeChecker.atMethodCallCore(TypeChecker.java:749)
    at javassist.compiler.TypeChecker.atNewExpr(TypeChecker.java:149)
    at javassist.compiler.ast.NewExpr.accept(NewExpr.java:73)
    at javassist.compiler.TypeChecker.atFieldAssign(TypeChecker.java:276)
    at javassist.compiler.JvstTypeChecker.atFieldAssign(JvstTypeChecker.java:84)
    at javassist.compiler.TypeChecker.atAssignExpr(TypeChecker.java:230)
    at javassist.compiler.ast.AssignExpr.accept(AssignExpr.java:39)
    at javassist.compiler.CodeGen.doTypeCheck(CodeGen.java:242)
    at javassist.compiler.CodeGen.atStmnt(CodeGen.java:330)
    at javassist.compiler.ast.Stmnt.accept(Stmnt.java:50)
    at javassist.compiler.Javac.compileStmnt(Javac.java:567)
    at javassist.CtConstructor.insertBeforeBody(CtConstructor.java:261)
    ... 49 more

Misc

There isn't anything special about my app, especially with what I'm trying to do here.

[cincospenguinos]

It looks like a good workaround for this issue is to specify a type of List--I changed those fields from List to ArrayList and everything works fine. Regardless, I think overriding the List relation type should work fine, but that of course is up to you guys.

[greenrobot]

Maybe we can detect the @Convert and skip it for relation detection, @greenrobot-team ?

[greenrobot-team]

The processor correctly ignores @Convert fields of type List. But the bytecode transformer does not. Guess that bug slipped by, because we have no tests where @Convert is of type List. 😱

Will add those now and work on fix.
-ut

[greenrobot-team]

Alright, added tests and built fix. This should be released with the next preview (or final) release of 2.0.0.

Please re-open if the next release does not fix this issue.
-ut

[greenrobot]

Try with 2.0.0-beta2