Calculation of attribute value from aggregation of two associated entity (not composition)

Support
#1

I have three entities -
First entity is HZW with name and inventory attribute.

Second entity HZdisposal have n-1 association with HZW and attribute date, HZW, disposedQuantity.

Third entity HZgeneration have n-1 association with HZW and attribute date, HZW, generatedQuantity.

What is the best method to recalculate HZW,inventory whenever there are addition, deletion or edit in HZdisposal and HZgeneration entities.

Thanks

#2

I tried it by using postcommit in both HZgenerationEdit and HZdisposalEdit and using nativequery in service bean.

@Subscribe(target = Target.DATA_CONTEXT)
private void onPostCommit(DataContext.PostCommitEvent event) {
    HazardousWasteService.updateInventory(getEditedEntity().getHazardousWaste());
}

but it is giving exception - NullPointerException on this line
HazardousWasteService.updateInventory(getEditedEntity().getHazardousWaste());

The service bean interface is

package com.company.sheeloffice.service;

import com.company.sheeloffice.entity.HazardousWaste;

public interface HazardousWasteService {
    String NAME = "sheeloffice_HazardousWasteService";
    void updateInventory(HazardousWaste HazardousWaste);
}

Bean usesw nativequery for calculating total generation and total disposal for particular HazardousWaste (HZW) and calculate inventory and save it the database using nativequery again.

thanks in advance

#3

Please delete my reply as it was due to variable name.

I am able to get the desired results by nativesql but is there a better method using cuba framework?

Secondly in below code used

    Query query = em.createNativeQuery(
                        "select sum(o.Quantity) from SHEELOFFICE_HAZARDOUS_WASTE_GENERATION o where o.HAZARDOUS_WASTE_ID = #login");
                query.setParameter("login", MyParameter);
                tg = (double) query.getSingleResult() ;

this line " tg = (double) query.getSingleResult() " gives exception if there is no data in database. How I can solve this issue.
PS: I am new to java and cuba

Thanks

#4

This code solved the issue

tg = (query.getSingleResult()==null) ? 0:(double) query.getSingleResult();

I am able to get the desired results by nativesql but is there a better method using cuba framework?

Thanks and regards

#5

You can use DataManager and JPQL:

BigDecimal sum = dataManager.loadValue(
        "select sum(o.amount) from demo$Order o " +
        "where o.date >= :date group by o.customer", BigDecimal.class)
    .parameter("date", orderDate)
    .one();