5 Creating services - Reference Documentation

Authors: Alejandro García Granados

Version: 0.4

5 Creating services

Almost all the Java Web Applications consider a "service" tier where the application logic takes place and Grails applications are included, but currently there isn't a "scaffolded" way to generate them. The Optimus plugin lets you do this, including the generation of the corresponding unit tests (as we explained in the following section).

You have to execute the create-service-class command:

grails create-service-class [domainClass]

Suppose you have a class named mypackage.Person. The class generated in grails-app/services/mypackage/PersonService.groovy will look like this:

package mypackageimport grails.gorm.DetachedCriteria
import grails.validation.ValidationException
class PersonService {
    Map list( Map params ) {
        processParams( params )
        def criteria = new DetachedCriteria( Person ).build {}
        [ items:criteria.list( params ), total:criteria.count() ]
    }
    void create( Person person ) {
        save( person )
    }
    void update( Person person ) {
        save( person )
    }
    Person get( Long id ) {
        if ( id == null ) throw new IllegalArgumentException(
            "Parameter 'id' is null" )
        Person.findById( id )
    }
    void delete( Person person ) {
        if ( person == null ) throw new IllegalArgumentException(
            "Parameter 'person' is null" )
        person.delete()
    }
    private void processParams( params ) {
        params.max = ListUtils.parseMax( params.max )
        params.offset = ListUtils.parseOffset( params.offset )
        params.order = ListUtils.parseOrder( params.order )
        def fields = [ 'name', 'lastName', 'birthdate', 'enabled', 'id' ]
        params.sort = ListUtils.parseSort( params.sort, fields )
    }
    private void save( Person person ) {
        if ( !person ) throw new IllegalArgumentException(
            "Parameter 'person' is null" )
        try {
            person.save( failOnError:true )
        } catch ( ValidationException ) {
            throw new IllegalArgumentException(
                "Parameter 'person' is invalid" )
        }
    }
}

The plugin generates the necessary methods for all the CRUD operations. As you probably realize, there is a class called in the processParams method named ListUtils. This class is automatically generated and placed in the src/groovy/mypackage/ListUtils.groovy file, and it contains utility methods for the list service method:

package mypackageclass ListUtils {
    static Integer parseMax( String max ) {
        if ( max?.isInteger() && max != '0' ) {
            def maxInteger = new Integer( max )
            return Math.min( maxInteger, 10 )
        }
        10
    }
    static Integer parseOffset( String offset ) {
        if ( offset?.isInteger() ) {
            return new Integer( offset )
        }
        null
    }
    static String parseOrder( String order ) {
        if ( order == 'asc' || order == 'desc' ) {
            return order
        }
        null
    }
    static String parseSort( sort, fields ) {
        fields.find { it == sort }
    }
}

As you can see, this class avoids some common format problems, such as non-numeric values for "max" and "offset" properties, and constraints the fields that can be used with the "sort" property.

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5 Creating services - Reference Documentation

5 Creating services

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