Defining the Columns (Attributes) for Each Service Entity

An entity’s columns represent its attributes. These attributes map table fields to Java object fields. To add attributes for your entity, add <column /> tags to your entity definition:

<column name="guestbookId" primary="true" type="long" />

Service Builder creates a database field for each column you add to the service.xml file. It maps a database field type appropriate to the Java type specified for each column, and it does this across all the databases Liferay supports. Once Service Builder runs, it generates a Hibernate configuration that handles the object-relational mapping. Service Builder automatically generates getter/setter methods in the model class for these attributes. The column’s name specifies the name used in the getters and setters that are created for the entity’s Java field. The column’s type indicates the Java type of this field for the entity. If a column’s primary (i.e., primary key) attribute is set to true, the column becomes part of the primary key for the entity. If only one column has primary set to true, that column represents the entire primary key for the entity. This is the case in the Guestbook application. If you define multiple columns with the primary attribute set to true, the combination of columns makes up a compound primary key for the entity.

Note: The Implementing an Add Method article demonstrates how to generate unique primary keys for entity instances.

Create Entity Columns

Define the columns you need for your first entity. The Guestbook entity is simple: it has only two attributes; a primary key and a name:

<column name="guestbookId" primary="true" type="long" />
<column name="name" type="String" />

Note: On deploying a *service module, Service Builder automatically generates indexes for all entity primary keys.

Create a column for each attribute of your entity or entities, using the Java type you’ll use in your application. Service Builder handles mapping it to SQL for you.

Support Multi-tenancy

In addition to columns for your entity’s primary key and attributes, add portal instance ID and site ID columns. Then you can support Liferay’s multi-tenancy features, so that each portal instance and each Site in a portal instance can have independent sets of your application’s data. To hold the site’s ID, add a column called groupId of type long. To hold the portal instance’s ID, add a column called companyId of type long:

<!-- Group instance -->

<column name="groupId" type="long" />
<column name="companyId" type="long" />

Workflow Fields

You can support Liferay’s workflow system by adding the fields it needs to track an entity’s progress:

<!-- Status fields -->

<column name="status" type="int" />
<column name="statusByUserId" type="long" />
<column name="statusByUserName" type="String" />
<column name="statusDate" type="Date" />

Audit Entities

Finally, you can add columns to help audit your entities. To track each entity instance’s owner, add a column called userId of type long. Create a column named createDate of type Date to note an entity instance’s creation date. Add a column named modifiedDate of type Date to track the last time an entity instance was modified.

<!-- Audit fields -->

<column name="userId" type="long" />
<column name="userName" type="String" />
<column name="createDate" type="Date" />
<column name="modifiedDate" type="Date" />

Great! Your entities have columns that not only represent their attributes, but also support multi-tenancy, workflow, and auditing. Next, you’ll learn how to specify the relationship service entities.