Service Builder & Generated classes(relationships)

While working on the Service Builder in Liferay it’s good to have a clear picture of what all classes are generated by the Service Builder, how these classes are related to each other, where can I put my custom code, how can I invoke persistence layer methods.

In this post I intend to answer some of the questions in a very simplistic view – the very basics in plain English.

I’ll take an example. I have created a very basic service.xml.

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE service-builder PUBLIC "-//Liferay//DTD Service Builder 6.0.0//EN" "http://www.liferay.com/dtd/liferay-service-builder_6_0_0.dtd">

<service-builder package-path="com.ab">

      <author>gaurshar</author>

      <namespace>B</namespace>

     

      <entity name="Student" local-service="true" remote-service="false">

            <column name="studentId" type="long" primary="true" id-type="class" id-param="com.liferay.counter.service.persistence.IDGenerator"></column>

          <column name="studentName" type="String"></column>

            <column name="classId" type="long"/>    

             <finder return-type="Collection" name="StudentName">

          <finder-column name="studentName"></finder-column>

       </finder>

      </entity>

     

      <entity name="Classroom" local-service="true" remote-service="false">

            <column name="classId" type="long" primary="true" id-type="class" id-param="com.liferay.counter.service.persistence.IDGenerator"></column>

          <column name="className" type="String"></column>

          <column name="student" type="Collection" entity="Student" mapping-key="studentId"></column>

           <finder return-type="Collection" name="ClassName">

          <finder-column name="className"></finder-column>

       </finder>

      </entity>

     

</service-builder>

Few points to highlight –

1) There are two entities – Student and Classroom

2) There is a one-to-many relation defined between Classroom and Student

3) There are few finder methods defined

When we build the service through Service Builder, the framework generates a set of classes as depicted in the diagram below. 

Few things to note here –

1) All the column name mappings, getters and setters are defined in ClassroomLocalServiceBaseImpl.

2) ClassroomLocalServiceImpl does not contain any method by default and should contain any custom methods (more on it sortly…)

3) Custom service classes, jsps, controllers should use ClassroomLocalServiceUtil class for accessing any service, persistence related methods.

This class should be the single point of contact for our code .

4) There is a parallel structure for Persistence layer generated by Service Builder. There is an abstraction in terms of ClassroomUtil that wraps all the methods of the persistence layer and provides a single point of contact for Service Layer classes.

5) We should not directly invoke methods of any of the persistence layer classes including the ClassroomUtil class.

 If we need to invoke a method of ClassroomUtil, we must do the following –

•  Taking the above example, we have a method in ClassroomUtil – getStudents(long pk) that returns all the students in a class. We should create a method ‘getStudents’ in ClassroomLocalServiceImpl (class where all the custom methods are written). This method calls ClassroomUtil.getStudents() method

•  Regenerate the service classes using Service Builder. This regenerates the service layer classes and creates a method getStudents() in ClassroomLocalServiceUtil. This can now be invoked from custom code.

     Remember the bottom line is ‘ClassroomLocalServiceUtil’ should be the single point of contact for custom code.

Invoking persistence layer methods from Service layer sets up transaction context and hibernate sessions. 

Thanks

Srikanth