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asXML - 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 XML 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. This key is used by the representation of the associated reference variables in values to reference the attribute. 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. In the first column here, classes stands for http://www.sap.com/abapxml/classes. For identifiers PRG, CPOOL, and FPOOL, the same substitution rule applies as that for 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 group fpool

The serializable values of an instance of a class (instance attributes or output parameters of a special helper method) are displayed 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 point (.), to distinguish it from a class attribute of the same name. For the identifiers, the same substitution rules apply as for 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 environment the serializability of a class and its subclasses and allows it to declare 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 from 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 help methods. Static attributes are ignored in serializations or deserializations (with the exception of 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 specified by the class in which instance attributes are declared or into which an interface that contains instance attributes is integrated. 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 the interface IF_SERIALIZABLE_OBJECT. Name part is the name of the respective class. If the class is a local class, prefix local is added in front of the name, separated by a point (.), to distinguish it from a global class of the same name. 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.

In deserializations, an object of the respective class is created. Here, 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 corresponding XML elements. Here the order of the object parts and the attributes is not important. Instance attributes without a corresponding XML element retain their value. Unnecessary XML elements are ignored as long as they do not belong to a namespace; otherwise they raise an exception that can be handled. In the deserialization of an element that does not have any subelements part, no object is created but instead the target reference variable is initialized.

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 XML element part. In deserializations, the attribute value is currently not evaluated but is intended for possible future enhancements.

Note

Using the standard behavior involves a certain security risk, because all instance attributes of an object can be serialized and can be manipulated in the XML data that is 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, 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:

If 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, 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, where the values of the subelements of the corresponding element part are passed to the input parameters of the methods that have the same name. The order does not matter here and unnecessary XML elements are ignored.

Executable Example

Modified Serialization and Deserialization



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Example Modified Serialization and Deserialization