3.7.2. Drag & Drop

Internal use

Internal M This topic is intended for MetaFactory developers only

Steps to implement the feature

Drag & Drop of an item in a list involves a dragable object (e.g. ‘Subtask’) and a reference to a parent object (e.g. ‘Task’).

In order to implement this feature take the following steps:

  1. Add metadata to the draggable object to mark it orderable within a certain reference (e.g. reference ‘task’ )

    Listing 3.11 model.xml
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    <object name="Subtask">
        <metadata>
                ...
                <orderable>task</orderable>
        </metadata>
        ...
        <reference name="task" type="Task">
                ...
        </reference>
</object>

    Exclam M In the <orderable> metadata you need to specify the name of a reference, not the name of an object.

  2. Add an attribute sortOrder to the draggable object (here object Subtask)

    Listing 3.12 model.xml
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    <object name="Subtask">
        <metadata>
                <orderable>task</orderable>
        </metadata>
        ...
        <attribute name="sortOrder" type="Integer" notnull="true">
                <metadata>
                        <entity.default.value>Integer.MAX_VALUE</entity.default.value>
                        <list.relation.mgmt>[number]</list.relation.mgmt>
                </metadata>
        </attribute>
        <reference name="task" type="Task">
                <metadata>
                        ...
                </metadata>
        </reference>
</object>

  3. Add metadata to the reference to create a finder (e.g. findByTask)

    Listing 3.13 model.xml
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    <object name="Subtask">
        <metadata>
                ...
                <orderable>task</orderable>
        </metadata>
        ...
        <attribute name="sortOrder" type="Integer" notnull="true">
                <metadata>
                        <entity.default.value>Integer.MAX_VALUE</entity.default.value>
                        <list.relation.mgmt>[number]</list.relation.mgmt>
                </metadata>
        </attribute>
        <reference name="task" type="Task">
                <metadata>
                        ...
                        <create.finder.method.list>true</create.finder.method.list>
                </metadata>
        </reference>
</object>

  4. Generate the application

  5. Create a changeSet in the Liquibase alters changelog to add the column to the table of the draggable object.

    Set a default value of 0 as the sort_order is required and must not be null. On the entity the default value becomes Integer.MAX_VALUE, however this is not supported by SQL. 0 is fine to start with.

    Listing 3.14 [projectdir]\[backenddir]\src\main\resources\config\liquibase\liquibase-alters-changeLog.xml
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    <databaseChangeLog ...>
        ...
        <changeSet id="[id-named-after-jira-issue]" author="[your-initials]">
                <addColumn tableName="subtask">
                        <column name="sort_order" type="INT" defaultValueNumeric="0">
                                <constraints nullable="false" />
                        </column>
                </addColumn>
        </changeSet>
</databaseChangeLog>

    Glasses M Read more about Liquibase change sets

  6. Run the application.