Form Processor Filters - Alfresco Content Services - 23.4 - 23.4 - Ready - Alfresco - external

Form Processor filters can be used to modify submitted form data before and after persistence. They can also be used to manage form fields before and after form generation.

Architecture Information: Software Architecture

Form Processor filters are typically used to add custom processing to a form processor. If you are new to how forms are persisted and generated, and how filters plays into that, then read the Form Processor extension point docs before proceeding.

Here are a number of use-cases for form processor filters:

• Adding fields before the form is generated.
• Adding calculated fields after the default set of fields have been processed.
• Generating a unique identifier for a field before it’s stored in the database.
• Generate XML rendition of the metadata after the form data is stored in the database.
• Check field values before they are stored in the database.

A filter registry is associated with each Form Processor implementation that extends the FilteredFormProcessor class, each registered Filter is then called (within the same transaction) for each request processed by the FormProcessor.

It is the responsibility of the Filter to determine whether it is applicable for the request. The order in which the Filters are executed is not guaranteed.

Implementing a form processor filter requires a bit of Java programming. The following is an example of a filter that adds a property called prop_dueDateReadOnly, which is then used in a custom Form Control (for more information, see Form Controls) to determine if a Due Date should be read-only or not:

publicclassTaskFormFilterextendsAbstractFilter<WorkflowTask, WorkflowTask> {
    publicstaticfinal String DUEDATE_READONLY_PROP_NAME = "prop_dueDateReadOnly";

    @Override
    publicvoidbeforeGenerate(WorkflowTask workflowTask, List<String> fields, List<String> forcedFields,
                               Form form, Map<String, Object> context) {
        if (workflowTask != null) {
            boolean dueDateReadOnly = false;

            final FieldDefinition dueDateReadOnlyFieldDef = new PropertyFieldDefinition("dueDateReadOnly", "d:boolean");
            dueDateReadOnlyFieldDef.setDataKeyName(DUEDATE_READONLY_PROP_NAME);
            dueDateReadOnlyFieldDef.setProtectedField(true);
            dueDateReadOnlyFieldDef.setLabel("Due Date Read-only");
            form.addFieldDefinition(dueDateReadOnlyFieldDef);
            form.addData(DUEDATE_READONLY_PROP_NAME, dueDateReadOnly);
        }
    }

    @Override
    publicvoidafterGenerate(WorkflowTask workflowTask, List<String> fields, List<String> forcedFields,
                              Form form, Map<String, Object> context) {}

    @Override
    publicvoidbeforePersist(WorkflowTask workflowTask, FormData fieldDatas) {}

    @Override
    publicvoidafterPersist(WorkflowTask workflowTask, FormData fieldDatas, WorkflowTask workflowTask1) {}
}

By extending the AbstractFilter class the filter gets automatically registered with the form processor. The form filter class is parametrized so we can specialize the data type that the form is for upfront: Filter<ItemType, PersistType>. The above filter has been created assuming the form is for a Workflow Task: AbstractFilter<WorkflowTask, WorkflowTask>

After the filter class has been implemented we need to define a Spring Bean for it and at the same time specify which form processor we want to use:

<beanid="org.alfresco.training.repo.form.filter.taskFormFilter"class="org.alfresco.training.repo.forms.processor.TaskFormFilter"parent="baseFormFilter">
    <property name="filterRegistry" ref="taskFilterRegistry" />
</bean>

In this case we are using the taskFilterRegistry as we are dealing with a Workflow Task forms that are processed by the TaskFormProcessor. There are other filter registries that you need to use for form filters that deal with objects from content models:

• NodeFormProcessor: use the nodeFilterRegistry
• TypeFormProcessor: use the typeFilterRegistry

Defining a filter for a content model item and form looks something like this:

publicclassContentItemFormFilterextendsAbstractFilter<Object, NodeRef> {
    @Override publicvoidbeforeGenerate(Object item, List<String> fields, List forcedFields,
                                         Form form, Map<String, Object> context) {}
    @Override publicvoidafterGenerate(Object item, List<String> fields, List forcedFields,
                                        Form form, Map<String, Object> context) {}
    @Override publicvoidbeforePersist(Object item, FormData data) {}
    @Override publicvoidafterPersist(Object item, FormData data, NodeRef persistedObject) {}
}

This filter would be registered via the following Spring bean definition:

<beanid="org.alfresco.training.repo.form.filter.contentItemFormFilterEdit"class="org.alfresco.training.repo.forms.processor.ContentItemFormFilter"parent="baseFormFilter">
    <property name="filterRegistry" ref="nodeFilterRegistry" />
</bean>

This filter will actually only be invoked when you edit the content item (Node), if you want to also have the filter to be invoked when creating a content item (Node), then you have to also register it as follows:

<beanid="org.alfresco.training.repo.form.filter.contentItemFormFilterCreate"class="org.alfresco.training.repo.forms.processor.ContentItemFormFilter"parent="baseFormFilter">
    <property name="filterRegistry" ref="typeFilterRegistry" />
</bean>

The different methods that can be overridden, such as beforeGenerate, gives you the possibility to hook into the forms processing. They have the following meaning:

• beforeGenerate: Callback invoked before the form is generated/created. This is the place to add properties that should be used by for example form controls.
• afterGenerate: Callback invoked after the form has been generated for the given items and fields.
• beforePersist: Callback invoked before the form data is stored in the database. This method can be used to for example check the form fields.
• afterPersist: Callback invoked after the form data is stored in the database.