Key-Value Containers

KeyValueContainer and KeyValueCollectionContainer are designed to work with key-value entities. Such entities can contain an arbitrary number of attributes that are defined at runtime.

KeyValueContainer and KeyValueCollectionContainer can be defined in a view XML descriptor using keyValueInstance and keyValueCollection elements.

XML definition of a key-value container must include the properties element that defines the KeyValueEntity attributes (actually, keys and their types). The order of nested property elements should conform to the order of result set columns returned by the query. In the following example the username attribute will get its value from us.user.username column and the stepsCount attribute from count(us) column:

<keyValueCollection id="summaryDc">
    <loader id="summaryDl">
            <![CDATA[select us.user.username, count(us) from UserStep us
            where us.dueDate < current_date and us.completedDate is null
            group by us.user.username]]>
        <property name="username" datatype="string"/>
        <property name="stepsCount" datatype="int"/>

Besides, you can configure key-value containers using their Java API which includes the following methods:

  • addProperty() - allows you to define the entity attributes (keys). The method accepts a name of the attribute and its type in the form of a Datatype or a Java class. In the latter case, the class should be either an entity class or a class supported by one of the datatypes. This method is used by the framework under the hood when you define properties of the key-value container declartively in XML as explained above.

  • setIdName() is an optional method that allows you to define one of the attributes as an identifier attribute of the entity. It means that KeyValueEntity instances stored in this container will have identifiers obtained from the given attribute. Otherwise, KeyValueEntity instances get randomly generated UUIDs.

  • getEntityMetaClass() returns a dynamic implementation of the MetaClass interface that represents the current schema of KeyValueEntity instances. It is determined by previous calls to addProperty().