Adding Model Hints

Adding Model Hints

Once you’ve used Service Builder to define model entities, you may want to refine how users enter that data. Model hints specify entity data restrictions and other formatting. For example, model hints can define a calendar field with dates selectable in the future only.

You define model hints in a file called portlet-model-hints.xml. The portlet-model-hints.xml file goes in the service module’s src/main/resources/META-INF folder.

Model hints define two things:

  1. How entities are presented to users

  2. The size of database columns

As Liferay renders your form fields, it customizes the form’s input fields based on your configuration.


If you chose Spring as the dependency injector, Service Builder generates a number of XML configuration files in your service module’s src/main/resources/META-INF folder. Service Builder uses most of these files to manage Spring and Hibernate configurations. Don’t modify the Spring or Hibernate configuration files; changes to them are overwritten when Service Builder runs. You can however, safely edit the portlet-model-hints.xml file.

As an example, consider the Blogs app service module’s model hints file:

<?xml version="1.0"?>

	<model name="com.liferay.blogs.model.BlogsEntry">
		<field name="mvccVersion" type="long" />
		<field name="ctCollectionId" type="long" />
		<field name="uuid" type="String" />
		<field name="externalReferenceCode" 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="title" type="String">
			<hint name="max-length">255</hint>
			<sanitize content-type="text/plain" modes="ALL" />
			<validator name="required" />
		<field name="subtitle" type="String">
			<hint-collection name="TEXTAREA" />
		<field name="urlTitle" type="String">
			<hint name="max-length">255</hint>
		<field name="description" type="String">
			<hint-collection name="TEXTAREA" />
			<hint name="display-width">350</hint>
		<field name="content" type="String">
			<hint-collection name="CLOB" />
			<sanitize content-type="text/html" modes="ALL" />
		<field name="displayDate" type="Date" />
		<field name="allowPingbacks" type="boolean" />
		<field name="allowTrackbacks" type="boolean" />
		<field name="trackbacks" type="String">
			<hint-collection name="CLOB" />
		<field name="coverImageCaption" type="String">
			<hint-collection name="TEXTAREA" />
			<sanitize content-type="text/html" modes="ALL" />
		<field name="coverImageFileEntryId" type="long" />
		<field name="coverImageURL" type="String">
			<hint-collection name="URL" />
		<field name="smallImage" type="boolean" />
		<field name="smallImageFileEntryId" type="long" />
		<field name="smallImageId" type="long" />
		<field name="smallImageURL" type="String">
			<hint-collection name="URL" />
			<hint name="display-width">210</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" />

The root-level element is model-hints. 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 class name. Models have field elements representing their entity’s columns. Finally, field elements must have a name and a type. Each field element’s name and type maps to the name and type specified for the entity’s column in the service module’s service.xml file. Service Builder generates all these elements for you, based on the service.xml.

To add hints to a field, add a hint child element. For example, you can add a display-width hint to specify the pixel width to use in displaying 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, run Service Builder again and redeploy your module. 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 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.

Model Hint Types

The following table describes the portlet model hints available for use.

Model Hint Values and Descriptions

Name Value Type Description Default
auto-escape boolean sets whether text values should be escaped via HtmlUtil.escape true
autoSize boolean displays the field in a for scrollable text area false
day-nullable boolean allows the day to be null in a date field false
default-value String sets the default value of the form field rendered using the aui taglib (empty String)
display-height integer sets the display height of the form field rendered using the aui taglib 15
display-width integer sets the display width of the form field rendered using the aui taglib 350
editor boolean sets whether to provide an editor for the input false
max-length integer sets the maximum column size for SQL file generation 75
month-nullable boolean allows the month to be null in a date field false
secret boolean sets whether to hide the characters input by the user false
show-time boolean sets whether to show the time along with the date true
upper-case boolean converts all characters to upper case false
year-nullable boolean allows a date field’s year to be null false
year-range-delta integer specifies the number of years to display from today’s date in a date field rendered with the aui taglib 5
year-range-future boolean sets whether to include future dates true
year-range-past boolean sets whether to include past dates true

The aui taglib is fully supported and not related to AlloyUI (the JavaScript library) that’s deprecated.


You can use a mix of Clay and aui tags in a form. Model hints, however, affect aui tags only.

Note that Liferay DXP/Portal has its own model hints file portal-model-hints.xml. It’s in portal-impl.jar’s META-INF folder. This file contains many hint examples, so you can reference it when creating portlet-model-hints.xml files.

Default Hints

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 pixels to each field:

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

Hint Collections

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="EMAIL-ADDRESS">
    <hint name="max-length">254</hint>
<hint-collection name="HOSTNAME">
    <hint name="max-length">200</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" />

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, redeploy your project, and check that the hints defined in your hint collection have taken effect.

Nice work! 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.