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ABENASXML_CLASS_INSTANCES - ASXML CLASS INSTANCES

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- Instances of Classes

To transform classes to XML using the statement CALL TRANSFORMATION, or to create classes from XML data, their classes must implement the interface IF_SERIALIZABLE_OBJECT. The instance of a class (object) is represented as a subelement of heap as follows:

  asx:heap xmlns:nspace ...>
    class id = "key">
      part classVersion = "...">
        name>.../name>
        ...
      /part>
      ...
    /class>
  /asx:heap>

The class element name is the schema type name of the class of the object (or the dynamic type of the reference variables) from the nspace namespace (see table below) in uppercase letters. The mandatory attribute id contains the unique key key of the element used to reference it by the representation of the associated reference variables in values. The subelements part>.../part> contain the values of the instance attributes of individual object parts as subelements name>.../name>. The individual object parts are defined by means of the serializable classes of the current inheritance hierarchy.

The namespace of the class name indicates where the class is defined. The table below shows the possible namespaces, whereby in the first column, classes stands for http://www.sap.com/abapxml/classes. The same substitution rule applies to the identifiers PRG, CPOOL, and FPOOL as to the namespaces for anonymous data objects.

Namespace	Where Defined
classes/global	Class Library
classes/program/PRG	Program PRG
classes/class-pool/CPOOL	Class Pool CPOOL
classes/function-pool/FPOOL	Function pool FPOOL

The serializable values of an instance of a class (instance attributes or output parameters of a special helper method) are represented in the asXML representation for named data objects or for reference variables as the content or attributes of name>.../name>. Here, name is the name of an instance attribute or output parameter in uppercase letters. For interface attributes, the name of the interface is added before the name, separated by a period (.), to distinguish it from an identically named class attribute. The same substitution rules apply to the identifiers as to all elements.

The serializable values of an instance of a class are specified in the class by implementing the system interface IF_SERIALIZABLE_OBJECT. The system interface IF_SERIALIZABLE_OBJECT is a tag interface. Its implementation shows the runtime framework the serializability of a class and its subclasses and allows the declaration of certain other components in the class according to fixed syntax rules. This interface IF_SERIALIZABLE_OBJECT can only be implemented in one class of a path and is effective for all subclasses as of this class.

If the class or one of its superclasses does not implement the interface IF_SERIALIZABLE_OBJECT, the element class does not contain any subelements. By default, all instance attributes of a class in which the interface IF_SERIALIZABLE_OBJECT is implemented directly or in a superclass are serialized and deserialized to this class. This behavior can be changed by declaring special helper methods. Static attributes are ignored in serializations or deserializations (except for the special constant SERIALIZABLE_CLASS_VERSION).

Standard Behavior

If the class or one of its superclasses implements the interface IF_SERIALIZABLE_OBJECT, the element class>.../class> contains at least one subelement part>.../part>/class>. These subelements correspond to individual serializable object parts and contain the representations of the instance attributes of the respective object part in asXML format. An object part is determined by the class in which instance attributes are declared or in which an interface that contains instance attributes is implemented. A serializable class contains an object part for itself as well as object parts for all superclasses in the current path of the inheritance tree up to and including the class that implements interface IF_SERIALIZABLE_OBJECT. The name part is the name of the respective class. If the class is a local class, the prefix local is added in front of the name, separated by a period (.), to distinguish it from an identically named global class. Object parts of superclasses in which the interface IF_SERIALIZABLE_OBJECT is not implemented are not serializable and do not have a corresponding subelement part. This means that a class in which the interface IF_SERIALIZABLE_OBJECT is not implemented (neither in the class itself nor in a superclass) creates an empty XML element class in serializations.

In serializations, the XML elements part of the object parts of the superclasses that implemented the interface IF_SERIALIZABLE_OBJECT are created for the subclasses and by default the XML elements of the instance attributes are created in the order in which they are declared in the class.

During deserialization, an object of the respective class is generated, whereby the instance constructor is not executed. After the object is created, all instance attributes have their initial value or the start value that is specified using the addition VALUE of the statement DATA. By default, the instance attributes are supplied with the values of the associated XML elements, whereby the order of the object parts and the attributes is not important. Instance attributes without a corresponding XML element retain their value. Superfluous XML elements are ignored if they do not belong to a namespace and otherwise raise a catchable exception. During the deserialization of an element with no subelements part, no object is created and the target reference variable is initialized instead.

If a class or one of its superclasses implements the interface IF_SERIALIZABLE_OBJECT, the private constant SERIALIZABLE_CLASS_VERSION of type i can be declared in each object part, that is, in each participating class of the inheritance tree. In serializations, the value of the constant is assigned to attribute classVersion of the XML element part. In deserializations, the attribute value is currently not evaluated but is intended for possible future enhancements.

Note

Using the standard behavior poses a certain security risk because all instance attributes of an object can be serialized and can be manipulated in the XML data created (see executable example).

Adjusted Behavior

By default, all instance attributes of an object part are serialized regardless of their visibility and the version of the class is checked. To change this behavior, for each object part, the instance methods SERIALIZE_HELPER and DESERIALIZE_HELPER can be declared and implemented in the respective class. These methods can only be declared as private instance methods in classes that implement the interface IF_SERIALIZABLE_OBJECT directly or in one of its superclasses. The declaration of one of the methods restricts the declaration of the others, and the interface is predefined by the syntax check as described below:

The method SERIALIZE_HELPER is only allowed to have output parameters, and the method DESERIALIZE_HELPER is only allowed to have input parameters with generic typing.

For each output parameter of method SERIALIZE_HELPER, there must be an identically named input parameter of method DESERIALIZE_HELPER with the same typing. Additional input parameters of method DESERIALIZE_HELPER must be optional.

The method SERIALIZE_HELPER must not have any output parameters of name SERIALIZABLE_CLASS_VERSION, and the method DESERIALIZE_HELPER is allowed to have an optional input parameter of type i, which is currently not used but is intended for possible future enhancements.

If the methods SERIALIZE_HELPER and DESERIALIZE_HELPER are declared in an object part, the instance attributes of the object part are not serialized and deserialized. Instead, in serializations, the method SERIALIZE_HELPER is executed, and the values of all output parameters are written to the corresponding element part as subelements in the order specified in asXML format. The name of a subelement is the name of the corresponding output parameter in uppercase letters. In deserializations, the method DESERIALIZE_HELPER is called and the values of the subelements of the corresponding element part are passed to the input parameters of the identically named methods. The order does not matter here, and superfluous XML elements are ignored.

Adjusted Serialization and Deserialization

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