Customizing Model Entities With Model Hints

If you’ve already used Service Builder to define your model entities and have implemented business logic for creating and modifying those entities, you might have some ideas for helping users to submit valid model entity data. For example, suppose you’re working on a calendar app where users can select a date for a calendar event. How can you specify that only future dates are selectable? Easy! Use portlet model hints! Liferay Service Builder’s model hints provide a single place in your application where you can specify entity data restrictions. Model hints are specified in a single file called portlet-model-hints.xml in your project. If your project is comprised of an API module, a service module, and a web module, as is common for Liferay DXP 7.0 applications, portlet-model-hints.xml should go in the service module. For example, in Liferay’s Bookmarks application, the portlet-model-hints.xml file goes in the bookmarks-service/src/main/resources/META-INF/ folder. Model hints are referred to as such because they suggest how entities should be presented to users. Model hints let you to configure how the AlloyUI tag library, aui, shows model fields. As Liferay displays form fields in your application, it first checks the model hints you specified and customizes the form’s input fields based on these hints. Model hints can also be used to specify the size of the database columns used to store the entities and to specify other entity details.

As an example, consider the Bookmarks app’s model hints file:

<?xml version="1.0"?>

    <model name="com.liferay.bookmarks.model.BookmarksEntry">
        <field name="uuid" type="String" />
        <field name="entryId" type="long" />
        <field name="groupId" type="long" />
        <field name="companyId" type="long" />
        <field name="userId" type="long" />
        <field name="userName" type="String" />
        <field name="createDate" type="Date" />
        <field name="modifiedDate" type="Date" />
        <field name="resourceBlockId" type="long" />
        <field name="folderId" type="long" />
        <field name="treePath" type="String">
            <hint name="max-length">4000</hint>
        <field name="name" type="String">
            <hint name="max-length">255</hint>
        <field name="url" type="String">
            <hint-collection name="URL" />
            <validator name="required" />
            <validator name="url" />
        <field name="description" type="String">
            <hint-collection name="TEXTAREA" />
        <field name="visits" type="int" />
        <field name="priority" type="int">
            <hint name="display-width">20</hint>
        <field name="lastPublishDate" type="Date" />
        <field name="status" type="int" />
        <field name="statusByUserId" type="long" />
        <field name="statusByUserName" type="String" />
        <field name="statusDate" type="Date" />
    <model name="com.liferay.bookmarks.model.BookmarksFolder">

The root-level element is model-hints. All the model entities are represented by model sub-elements of the model-hints element. Each model element must have a name attribute specifying the fully-qualified model class name. Each model has field elements representing its model entity’s columns. Lastly, each field element must have a name and a type. Each field element’s names and types correspond to the names and types specified for each entity’s columns in the service module’s service.xml file. Service Builder generates all these elements for you, based on service.xml.

To add hints to a field, add a hint tag inside its field tag. For example, you can add a display-width hint to specify the pixel width used to display the field. The default pixel width is 350. To show a String field with 50 pixels, you could nest a hint element named display-width and give it a value of 50.

To see the effect of a hint on a field, you must run Service Builder again and redeploy your project. Note that changing display-width doesn’t limit the number of characters a user can enter into the name field; it only controls the field’s width in the AlloyUI input form.

To configure the maximum size of a model field’s database column (i.e., the maximum number of characters that can be saved for the field), use the max-length hint. The default max-length value is 75 characters. If you want the name field to persist up to 100 characters, add a max-length hint to that field:

<field name="name" type="String">
    <hint name="display-width">50</hint>
    <hint name="max-length">100</hint>

Remember to run Service Builder and redeploy your project after updating the portlet-model-hints.xml file.

So far, you’ve seen a few different hints. The following table describes the portlet model hints available for use.

Model Hint Values and Descriptions

NameValue TypeDescriptionDefault
auto-escapebooleansets whether text values should be escaped via HtmlUtil.escapetrue
autoSizebooleandisplays the field in a for scrollable text areafalse
day-nullablebooleanallows the day to be null in a date fieldfalse
default-valueStringsets the default value of the form field rendered using the aui taglib(empty String)
display-heightintegersets the display height of the form field rendered using the aui taglib15
display-widthintegersets the display width of the form field rendered using the aui taglib350
editorbooleansets whether to provide an editor for the inputfalse
max-lengthintegersets the maximum column size for SQL file generation75
month-nullablebooleanallows the month to be null in a date fieldfalse
secretbooleansets whether to hide the characters input by the userfalse
show-timebooleansets whether to show the time along with the datetrue
upper-casebooleanconverts all characters to upper casefalse
year-nullablebooleanallows a date field’s year to be nullfalse
year-range-deltaintegerspecifies the number of years to display from today’s date in a date field rendered with the aui taglib5
year-range-futurebooleansets whether to include future datestrue
year-range-pastbooleansets whether to include past datestrue

Note that Liferay has its own portal-model-hints.xml file. This file contains many hint examples, so you can reference it when customizing your portlet-model-hints.xml file.

You can use the default-hints element to define a list of hints to apply to every field of a model. For example, adding the following element inside a model element applies a display-width of 300 to each field:

    <hint name="display-width">300</hint>

You can define hint-collection elements inside the model-hints root-level element to define a list of hints to apply together. A hint collection must have a name. For example, Liferay’s portal-model-hints.xml defines the following hint collections:

<hint-collection name="CLOB">
    <hint name="max-length">2000000</hint>
<hint-collection name="EDITOR">
    <hint name="editor">true</hint>
    <hint name="max-length">2000000</hint>
<hint-collection name="SEARCHABLE-DATE">
    <hint name="month-nullable">true</hint>
    <hint name="day-nullable">true</hint>
    <hint name="year-nullable">true</hint>
    <hint name="show-time">false</hint>
<hint-collection name="TEXTAREA">
    <hint name="display-height">105</hint>
    <hint name="display-width">500</hint>
    <hint name="max-length">4000</hint>
<hint-collection name="URL">
    <hint name="max-length">4000</hint>

You can apply a hint collection to a model field by referencing the hint collection’s name. For example, if you define a SEARCHABLE-DATE collection like the one above in your model-hints element, you can apply it to your model’s date field by using a hint-collection element that references the collection by its name:

<field name="date" type="Date">
    <hint-collection name="SEARCHABLE-DATE" />

As always, remember to run Service Builder and redeploy your project after updating your portlet-model-hints.xml file.

For example, suppose you want to use a couple of model hints in your project. Start by providing users with an editor for filling in their comment fields. To apply the same hint to multiple entities, define it as a hint collection. Then reference the hint collection in each entity.

To define a hint collection, add a hint-collection element inside the model-hints root element in your portlet-model-hints.xml file. For example:

<hint-collection name="COMMENT-TEXTAREA">
	<hint name="display-height">105</hint>
	<hint name="display-width">500</hint>
	<hint name="max-length">4000</hint>

To reference a hint collection for a specific field, add the hint-collection element inside the field’s field element:

<field name="comment" type="String">
	<hint-collection name="COMMENT-TEXTAREA" />

After defining hint collections and adding hint collection references, rebuild your services using Service Builder, redeploy your project, and check that the hints defined in your hint collection have taken effect.

Nice work! You’ve learned the art of persuasion through Liferay’s model hints. Now you can not only influence how your model’s input fields are displayed, but you can also can set its database table column sizes. You can organize hints, insert individual hints directly into your fields, apply a set of default hints to all of a model’s fields, or define collections of hints to apply at either of those scopes. You’ve picked up the “hints” on how Liferay model hints specify how to display app data!

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