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ABAP_SXML - Token-Based Parsing In token-based parsing, the parser iterates across all nodes (tokens) in the tree structure of the XML data, one after the other. By default, the iterator passes across all subnode branches until the final node. The parser pauses after every iteration step on a node whose properties are available in the attributes of the XML reader. If the parser pauses on the node for an element opening, the list of the XML attributes there can be accessed. ITOC
Basic Approach An XML reader is created using the factory method CREATE of the required class and by passing the source xml to the XML data, for example: DATA(reader) = cl_sxml_string_reader=>create( xml ). The static type of the reference variables is then the interface IF_SXML_READER and its methods and attributes can be addressed directly. In the simplest parsing case, the method NEXT_NODE is applied as many times as it takes to reach the end of the XML: reader->next_node( ). Once the method is called, the attributes of the reader with the required properties of the node can be accessed directly. If the parser is on the node of an element opening, the method NEXT_ATTRIBUTE can be used to iterate across the list of attributes of an XML element: reader->next_attribute( ). After this method, the attributes of the reader object contain the name and the value of the current XML attribute. The end of the data is represented by the value of the constants IF_SXML_NODE=>CO_NT_FINAL in the attribute NODE_TYPE. Any exceptions should be caught and handled in a TRY control structure. VX_EXA_ONLY
Example ABAP Coding
The class CL_DEMO_SXML_PARSE_XML executes a simple token-based parsing for any XML data that can be entered. ABAP_EXAMPLE_END
Methods for Token-Based Parsing In addition to the simple iteration across nodes and attributes, the interfaces IF_SXML_READER offers several other methods for token-based parsing, summarized below:
Methods for parsing using nodes
NEXT_NODE - Moves the parser to the next node
CURRENT_NODE - Resets the parser to the node for the element opening of the current node, if available. This method is ignored by value nodes or closed elements.
PUSH_NODE - Resets the parser to the node for the element opening of the direct parent node.
SKIP_NODE - Parses all nodes from a node for an element opening to the associated end of element. The parser is then at the end of the element. If required, the current node and all subnodes are passed to an XML writer. This method has no effect for value nodes or closed elements.
Methods for reading the attribute list
NEXT_ATTRIBUTE - Reads the next attribute in the list
NEXT_ATTRIBUTE_VALUE - Sets the attribute VALUE or VALUE_RAW of the read explicitly to the value of the current attribute
GET_ATTRIBUTE_VALUE - Sets the attribute VALUE of the reader to the value of a specific attribute
Latest notes:
The method CURRENT_NODE is most useful when reading an attribute list, to return to the start.
If an XML element has multiple identically named attributes, all of these attributes are respected in the order in which they appear (see example class CL_DEMO_XML_ATTRIBUTES )
Apart from simply skipping nodes, the method SKIP_NODE can also be used to check the subtrees or the entire tree for errors or to copy trees. In particular, the format of the copied tree or subtree can be transformed into a different format. NON_V5_HINTS
For the latter see the executable example.
Token-based parsing is designed mainly for forward iteration through the XML data. Free navigation, as possible in iXML Library in DOM, is not recommended here. The method PUSH_BACK makes it possible to move back a step but does not restore the reader to the state it had when it reached the node using NEXT_NODE. After a PUSH_BACK, the parsed node does not always produce the same result as the last time. In particular, subnodes already parsed could be skipped. ABAP_HINT_END
ABAP_EXAMPLES_ABEXA
Steps in Token-Based Parsing
Methods for token-based parsing ABAP_EXAMPLE_END
Attributes for Token-Based Parsing The attributes of the reader with the properties of the current node are:
NODE_TYPE - Node type in accordance with the constants of the interface IF_SXML_NODE
PREFIX - Namespace prefix
NAME - Element name
NSURI - Namespace
VALUE_TYPE - Type of the value in accordance with the constants of the interface IF_SXML_VALUE:
CO_VT_TEXT - Text data in the attribute VALUE
CO_VT_TEXT - Raw data in the attribute VALUE_RAW
VALUE - Character-like value (if text data)
VALUE_RAW - Byte-like value (if raw data) The value of the constants IF_SXML_NODE=>CO_NT_FINAL in the attribute NODE_TYPE indicate that the end of the XML data was reached.
Latest notes:
When parsing, the attributes of a reader are only overwritten by non-initial content. If the parser is set to a literal element without a name, for example, the preceding content of the attribute NAME is kept. This applies particularly to the attribute VALUE, which is not initialized if a node has no value.
The attributes are declared in the interface IF_SXML_READER. In a reader class, they can also be addressed using alias names. NON_V5_HINTS ABAP_HINT_END
