How to access partition properties in java ee batch / jberet

I have a job defined as below:

<step id="file-transfer">
    <chunk checkpoint-policy="item" item-count="10" retry-limit="10">
        <reader ref="allTrusteeCustomerFilesReader">
            <properties>
                <property name="part-page-first-offset" value="#{partitionPlan['part-page-first-offset']}"/>
                <property name="part-page-last-offset" value="#{partitionPlan['part-page-last-offset']}"/>
                <property name="part-page-length" value="#{partitionPlan['part-page-length']}"/>
                <property name="part-sort-field" value="#{partitionPlan['part-sort-field']}"/>
                <property name="part-sort-ascending" value="#{partitionPlan['part-sort-ascending']}"/>
            </properties>
        </reader>
        <processor ref="customerFileLocalToGoogleStorageProcessor"/>
        <writer ref="customerFileWriter">
            <properties>
                <property name="set-google-cloud-migrated" value="true"/>
            </properties>
        </writer>


        <skippable-exception-classes>
            <include class="be.valuya.gestemps.server.file.batch.error.NoLocalStorageDataException"/>
            <include class="be.valuya.gestemps.server.file.batch.error.TargetAlreadyPresentException"/>
            <include class="be.valuya.gestemps.server.file.batch.error.CustomerFileAlreadyMigratedException"/>
        </skippable-exception-classes>
        <retryable-exception-classes>
            <include class="be.valuya.gestemps.server.file.batch.error.TransferToGoogleFailedException"/>
        </retryable-exception-classes>
    </chunk>

    <partition>
        <mapper ref="customerFilePartitionMapper"/>
    </partition>

    <end on="COMPLETED"/>
</step>

The referenced mappers creates an Array of Properties, with defined values, and returns it:

    PartitionPlanImpl partitionPlan = new PartitionPlanImpl();
    partitionPlan.setPartitions(partitionCount);
    partitionPlan.setPartitionProperties(partitionProperties);

    return partitionPlan;

It is correctly called on step starts and returns properties with the correct keys defined.

However, Im not able to get the partition plan properties from my reader step. None of the job context properties nor the step context properties contains anything. I see no error in console. The job instance parameters only contains the parameters set at runtime. None of the parameters/properties names conflicts. Attempt to inject them using @BatchProperty leave the fields null.

The batch is started as follow:

    Properties properties = new Properties();
    // Fill parameters...
    long executionId = jobOperator.start(jobName, properties);

What am I missing?

The partition plan was puting integers in the Properties map. It seems strings are expected:

//
Properties partProperties;
partProperties.setProperty("plan-property", "20"); // <--- Use setProperty to enforce String values rather than put
// ...

PartitionPlanImpl partitionPlan = new PartitionPlanImpl();
partitionPlan.setPartitions(partitionCount);
partitionPlan.setPartitionProperties(partitionProperties);

return partitionPlan;