Custom Static Metadata

Available since version 1.1

We’ll use Static Metadata to reference the Metadata that is known at compile time an available from the types in the connector’s jar. Simple java types are part of this static Metadata, as well as custom POJOs defined by the developer in its model. The relevant part is that the structure is well known or can be introspected, without depending on other Parameters.

The advantage of static metadata over dynamic is that, because it does not change, there is no need to recalculate its structure. This means that the resolution is already done when developing an application.

When working with simple java types or POJOs as return or parameter types the SDK will create a proper static type for the element, but when your type is not defined as a java object (e.g. Json Schema, XSD, etc) you know exactly the structure of the type you are working with, you need to use the custom static metadata capabilities that the SDK provides.

XML and JSON Types

Operations may require parameters to be JSON or XML types that follow a certain structure (schema). It is possible to signal this to DataSense using the proper XSD or JSON schemas.

this will only work for InputStream and String java type parameters.

JSON Type

To determine the structure of a JSON type, a JSON schema must be provided.

@OutputJsonType

@OutputJsonType(schema = "person-schema.json")
public Result<InputStream, RetrieveAttributes> retrievePerson() {
  // ...
}

@AttributesJsonType

@AttributesJsonType(schema = "resolution-attributes-schema.json")
public Result<Integer, InputStream> getSolution() {
  // ...
}

@InputJsonType

public void addPerson(@InputJsonType(schema = "person-schema.json") InputStream person) {
  // ...
}

XML Type

To determine the structure of an XML, you must provide an XSD file and the qualified name that is used to reference the element to be loaded.

@OutputXmlType

@OutputXmlType(schema = "order.xsd", qname = "shiporder")
public Result<InputStream, OrderAttributes> retrieveOrder() {
  // ...
}

@AttributesXmlType

@AttributesXmlType(schema = "order-attributes.xsd", qname = "attributes")
public Result<Integer, InputStream> getOrderStatistics() {
  // ...
}

@InputXmlType

public void createOrder(@InputXmlType(schema = "order.xsd", qname = "shiporder") InputStream order) {
  // ...
}

Static Type Resolvers

The way to resolve custom static metadata for input parameters, output payload or output attributes is very similar and it is shown on the next examples:

On each example, the resolvers extends of an abstract class that implements StaticResolver. getStaticMetadata is the method that has to be implemented in order to resolve the metadata.

InputStaticTypeResolver

To use custom static metadata resolution on the input parameters of an operation, you must annotate the parameter with @TypeResolver and the value for the annotation must be a InputStaticTypeResolver.

This is an example of a InputStaticTypeResolver, it must implement the method getStaticMetadata:

public class JsonPersonInputStaticTypeResolver extends InputStaticTypeResolver {
  @Override
  public MetadataType getStaticMetadata() {
    ObjectTypeBuilder object = BaseTypeBuilder.create(MetadataFormat.JSON).objectType();
    object.id("json-object");
    object.addField().key("name").value().stringType();
    object.addField().key("last-name").value().stringType();
    return object.build();
  }
}

OutputStaticTypeResolver

to use custom static metadata resolution on the output payload of an operation, you must annotate the method with @OutputResolver and the output value for the annotation must be a OutputStaticTypeResolver.

This is an example of a OutputStaticTypeResolver, it must implement the method getStaticMetadata:

public class CsvOutputStaticTypeResolver extends OutputStaticTypeResolver {
  @Override
  public MetadataType getStaticMetadata() {
    return BaseTypeBuilder.create(MetadataFormat.CSV).objectType().id("csv-object").build();
  }
}

AttributesStaticTypeResolver

to use custom static metadata resolution on the output attributes of an operation, you must annotate the method with @OutputResolver and the attributes value for the annotation must be a OutputStaticTypeResolver.

This is an example of a AttributesStaticTypeResolver, it must implement the method getStaticMetadata:

public class CsvAttributesStaticTypeResolver extends AttributesStaticTypeResolver {

  @Override
  public MetadataType getStaticMetadata() {
    ObjectTypeBuilder object = BaseTypeBuilder.create(MetadataFormat.CSV).objectType();
    object.addField().key("location").value().stringType();
    object.addField().key("size").value().numberType();
    return object.build();
  }
}