Creating a Service - CUBA Platform. Developer’s Manual

4.4.1.1. Creating a Service

The name of service interface should end with Service, the names of implementation class – with ServiceBean.

The following steps are required for creating a service:

Create the service interface in the global module, as the service interface must be available at all tiers), and specify the service name in it. It is recommended to specify the name in the following format: {project_name}_{interface_name}. For example:
```
package com.sample.sales.core;

import com.sample.sales.entity.Order;

public interface OrderService {
    String NAME = "sales_OrderService";

    void calculateTotals(Order order);
}
```

Create the service class in the core module and add the @org.springframework.stereotype.Service annotation to it with the name specified in the interface:

package com.sample.sales.core;

import com.sample.sales.entity.Order;
import org.springframework.stereotype.Service;

@Service(OrderService.NAME)
public class OrderServiceBean implements OrderService {
    @Override
    public void calculateTotals(Order order) {
    }
}

The service class, being a managed bean, should be placed inside the package tree with the root specified in the context:component-scan element of the spring.xml file. In this case, the spring.xml file contains the element:

<context:component-scan base-package="com.sample.sales"/>

which means that the search for annotated beans for this application block will be performed starting with the com.sample.sales package.

Warning

Services are only intended for calling from outside of Middleware. Do not call service methods from other components of the middle tier. An error message is logged upon detection of a service call from another service.

If different services or other Middleware components require calling the same business logic, it should be extracted and encapsulated inside an appropriate managed bean. For example:

// service interface
public interface SalesService {
    String NAME = "sample_SalesService";

    BigDecimal calculateSales(UUID customerId);
}

// service implementation
@Service(SalesService.NAME)
public class SalesServiceBean implements SalesService {

    @Inject
    private SalesCalculator salesCalculator;

    @Transactional
    @Override
    public BigDecimal calculateSales(UUID customerId) {
        return salesCalculator.calculateSales(customerId);
    }
}

// managed bean encapsulating business logic
@Component
public class SalesCalculator {

    @Inject
    private Persistence persistence;

    public BigDecimal calculateSales(UUID customerId) {
        Query query = persistence.getEntityManager().createQuery(
                "select sum(o.amount) from sample$Order o where o.customer.id = :customerId");
        query.setParameter("customerId", customerId);
        return (BigDecimal) query.getFirstResult();
    }
}