Defining Global Service Information

A service’s global information applies to all its entities, so it’s a good place to start. In Liferay Dev Studio DXP, select the Service Builder node in the upper left corner of the Overview mode of your service.xml file. The main section of the view now shows the Service Builder form in which to enter your service’s global information. The fields include the service’s

Figure 1: This is the Service Builder form from the Bookmarks applications service.xml.

Figure 1: This is the Service Builder form from the Bookmarks application's `service.xml`.

Package Path

The package path specifies the package in which the service and persistence classes are generated. The package path for Bookmarks ensures that the *-api module’s service classes are generated in the com.liferay.bookmarks package. The persistence classes are generated in a package of the same name in the *-service module. For example, examine the Bookmarks application’s bookmarks-api and bookmarks-service modules to see how these are automatically generated for you. A later tutorial describes the package content.

Namespace Options

Service Builder uses the service namespace in naming the database tables it generates for the service. For example, Bookmarks could serve as the namespace for a Bookmarks application service.

<namespace>Bookmarks</namespace>

Service Builder uses the namespace in the following SQL scripts it generates in your src/main/resources/sql folder:

  • indexes.sql
  • sequences.sql
  • tables.sql

Service Builder uses the SQL scripts to create database tables for all the entities the service.xml defines. The database table names have the namespace prepended when they are created. Since the example namespace value is Bookmarks, the database table names created for the entities start with Bookmarks_ as their prefix. Each Service Builder project’s namespace must be unique. Separate plugins should use separate namespaces and should not use a namespace already used by Liferay entities (such as Users or Groups). Check the table names in Liferay’s database to see the namespaces already in use.

Warning: Use caution when assigning namespace values. Some databases have strong restrictions on database table and column name lengths. The Service Builder Gradle and Maven plugin parameter databaseNameMaxLength sets the maximum length you can use for your table and column names. Here are paraphrased examples of setting databaseNameMaxLength in build files:

Gradle build.gradle

buildService {
    ...
    databaseNameMaxLength = 64
    ...
}

Maven pom.xml

<configuration>
    ...
    <databaseNameMaxLength>64</databaseNameMaxLength>
    ...
</configuration>

Multiversion concurrency control (MVCC)

The service-builder element’s mvcc-enabled attribute is false by default. Setting mvcc-enabled="true" (hint: edit service.xml in Source view) enables multiversion concurrency control (MVCC) for all of the service’s entities. In systems, concurrent updates are common. Without MVCC people may read or overwrite data from an invalid state unknowingly. With MVCC, each modification is made upon a given base version number. When Hibernate receives the update, it generates an update SQL statement that uses a where clause to make sure the current data version is the version you expect.

If the current data version

  • matches the expected version, your data operation is based on up-to-date data and is accepted.

  • doesn’t match the expected version, the data you’re operating on is outdated. Liferay DXP rejects your data operation and throws an exception, which you can catch to help the user handle the exception (e.g., suggest retrying the operation).

Important: Enable MVCC for all your services by setting mvcc-enabled="true" in your <service-builder/> element. When invoking service entity updates (e.g., fooService.update(object)), make sure to do so in transactions. Propagate rejected transactions to the UI for the user to handle.

Author

As the last piece of global information, enter your name as the service’s author in your service.xml file. Service Builder adds @author annotations with the specified name to all the Java classes and interfaces it generates. Save your service.xml file. Next, you’ll add entities for your services.

« Creating the service.xml FileDefining Service Entities »
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