ABAP Keyword Documentation → ABAP - Reference → Data Interfaces and Communication Interfaces → ABAP and XML → Transformations for XML → asXML - Canonical XML Representation → asXML - Mapping of ABAP Data Types → asXML - Mapping of Reference Variables and Objects
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 displayed as a subelement of heap as follows:
<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. Mandatory attribute id contains unique key key of the element by means of which it is referenced by the display of the corresponding reference variables in values. 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. 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 display for named data objects or for reference variables as content or attributes of <name>...</name> whereby 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 differentiate 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).
Other versions: 7.31 | 7.40 | 7.54
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 displays 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 differentiate 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) generates 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 generated, whereby the instance constructor is not executed. After the object generation, all instance attributes have their
initial value or the
start value that is specified
with addition VALUE of 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. By default,
an exception that can be handled is raised in deserializations if the value of the attribute does not
match the value of the constant in the specified class. An object part can only be deserialized if the
values match or if neither the attribute nor the constant exists. This behavior can be changed by declaring special help methods.
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 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:
- Method SERIALIZE_HELPER is only allowed to have output parameters, and 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 input parameter of method DESERIALIZE_HELPER that has the same name and the same typing. Additional input parameters of method DESERIALIZE_HELPER have to be optional.
- Method SERIALIZE_HELPER is not allowed to have any output parameters of name SERIALIZABLE_CLASS_VERSION,
and method DESERIALIZE_HELPER is allowed to have this optional input parameter of type
i. In deserializations, this is supplied with the value of attribute classVersion of element part. This avoids the standard check made on the version.
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, method DESERIALIZE_HELPER is called, whereby 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.
Example