Data Model Versioning

REST API can handle data model changes. It is useful when, for example, some entity attribute was renamed, but REST API client doesn’t know about this modification and expects the attribute to have an old name.

For such cases REST API allows you to define transformation rules for entities JSON. If the client application sends the data model version in the request query parameter then the JSON in REST API method response or request body will be transformed according to transformation rules defined for that particular domain model version.

JSON transformation rules must be specified in files registered in cuba.rest.jsonTransformationConfig application property of the web or portal module (e.g in the web-app.properties file):

cuba.rest.jsonTransformationConfig = +com/company/myapp/rest-json-transformations.xml

The rest-json-transformations.xml file must be placed in the web or portal module (e.g. in package com.company.myapp). Its content is defined by the rest-json-transformations.xsd schema. File example:

<?xml version="1.0"?>
<transformations xmlns="http://schemas.haulmont.com/cuba/rest-json-transformations.xsd">

    <transformation modelVersion="1.0" oldEntityName="sales$OldOrder" currentEntityName="sales$NewOrder">
        <renameAttribute oldName="oldNumber" currentName="number"/>
        <renameAttribute oldName="date" currentName="deliveryDate"/>
        <toVersion>
            <removeAttribute name="discount"/>
        </toVersion>
    </transformation>

    <transformation modelVersion="1.0" currentEntityName="sales$Contractor">
        <renameAttribute oldName="summary" currentName="total"/>
        <renameAttribute oldName="familyName" currentName="lastName"/>
        <fromVersion>
            <removeAttribute name="city"/>
            <removeAttribute name="country"/>
        </fromVersion>
        <toVersion>
            <removeAttribute name="phone"/>
        </toVersion>
    </transformation>

    <transformation modelVersion="1.1" currentEntityName="sales$NewOrder">
        <renameAttribute oldName="date" currentName="deliveryDate"/>
    </transformation>

</transformations>

Standard transformers configured in the config file can perform the following transformations of entity JSON:

• rename entity
• rename entity attribute
• remove entity attribute

JSON transformation works for the following REST API endpoints:

• /entities - getting entities list, getting a single entity, entity create, entity update, entity delete
• /queries - entities JSON returned by the query will be transformed
• /services - JSON transformations will be applied both to entities returned by the service method and to entities passed as a service method argument

JSON transformations are applied if the request to the REST API contains the modelVersion URL parameter with the data model version number.

See the Data Model Versioning Example to understand how to configure data model versioning and use it from the client application.

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