Array containing the variable names that should be ignored by the codec.
Array containing the variable names that should be turned into or converted from references. See Codec.getId and Codec.getObject.
Maps from field names to XML attribute names.
Maps from XML attribute names to fieldnames.
Holds the template object associated with this codec.
StaticallowStatic global switch that specifies if expressions in arrays are allowed.
NOTE: Enabling this carries a possible security risk.
Sets the decoded child node as a value of the given object. If the object is a map, then the value is added with the given field name as a key. If the field name is not empty, then setFieldValue is called or else, if the object is a collection, the value is added to the collection. For strongly typed languages it may be required to override this with the correct code to add an entry to an object.
Hook for subclassers to post-process the object after decoding. This implementation returns the given object without any changes. The return value of this method is returned to the decoder from decode.
Hook for subclassers to post-process the node for the given object after encoding and return the post-processed node. This implementation returns the input node. The return value of this method is returned to the encoder from encode.
Hook for subclassers to pre-process the node for the specified object and return the node to be used for further processing by decode. The object is created based on the template in the calling method and is never null. This implementation returns the input node. The return value of this function is used in decode to perform the default decoding into the given object.
Hook for subclassers to pre-process the object before encoding. This returns the input object. The return value of this function is used in encode to perform the default encoding into the given node.
Converts booleans and numeric values to the respective types. Values are numeric if isNumericAttribute returns true.
Converts true to "1" and false to "0" is isBooleanAttribute returns true. All other values are not converted.
Parses the given node into the object or returns a new object representing the given node.
Dec is a reference to the calling decoder. It is used to decode complex objects and resolve references.
If a node has an id attribute then the object cache is checked for the object. If the object is not yet in the cache then it is constructed using the constructor of template and cached in Codec.objects.
This implementation decodes all attributes and childs of a node according to the following rules:
For add nodes where the object is not an array and the variable name is defined, the default mechanism is used, allowing to override/add methods as follows:
<Object>
<add as="hello"><![CDATA[
function(arg1) {
mxUtils.alert('Hello '+arg1);
}
]]></add>
</Object>
If no object exists for an ID in idrefs a warning is issued using GlobalConfig.logger.
Returns the resulting object that represents the given XML node or the object given to the method as the into parameter.
Decodes all attributes of the given node using decodeAttribute.
Decodes all children of the given node using decodeChild.
Calls decodeAttributes and decodeChildren for the given node.
Encodes the specified object and returns a node representing then given object. Calls beforeEncode after creating the node and afterEncode with the resulting node after processing.
Enc is a reference to the calling encoder. It is used to encode complex objects and create references.
This implementation encodes all variables of an object according to the following rules:
If no ID exists for a variable in idrefs or if an object cannot be encoded, a warning is issued using GlobalConfig.logger.
Returns the resulting XML node that represents the given object.
Encodes the value of each member in then given obj into the given node using encodeValue.
Converts the given value according to the mappings and id-refs in this codec and uses writeAttribute to write the attribute into the given node.
Returns the attribute name for the given field name. Looks up the value in the mapping or returns the input if there is no mapping for the given name.
Returns the field name for the given attribute name. Looks up the value in the reverse mapping or returns the input if there is no reverse mapping for the given name.
Returns the template instance for the given field. This returns the value of the field, null if the value is an array or an empty collection if the value is a collection. The value is then used to populate the field for a new instance. For strongly typed languages it may be required to override this to return the correct collection instance based on the encoded child.
Returns the name used for the node names and lookup of the codec when classes are encoded and nodes are decoded. For classes to work with this the codec registry automatically adds an alias for the classname if that is different from what this returns.
The default implementation returns the classname of the template class if no name is set.
Returns true if the given attribute is to be ignored by the codec. This implementation returns true if the given field name is in exclude or if the field name equals ObjectIdentity.FIELD_NAME.
Object instance that contains the field.
Fieldname of the field.
Value of the field.
Optionalwrite: booleanBoolean indicating if the field is being encoded or decoded. Write is true if the field is being encoded, else it is being decoded.
Returns true if the given field name is to be treated as a textual reference (ID). This implementation returns true if the given field name is in idrefs.
Object instance that contains the field.
Field name of the field.
Value of the field.
Optionalwrite: booleanBoolean indicating if the field is being encoded or decoded. Write is true if the field is being encoded, else it is being decoded.
Writes the given value into node using writePrimitiveAttribute or writeComplexAttribute depending on the type of the value.
Writes the given value as a child node of the given node.
Writes the given value as an attribute of the given node.
Generic codec for JavaScript objects that implements a mapping between JavaScript objects and XML nodes that maps each field or element to an attribute or child node, and vice versa.
Atomic Values
Consider the following example.
This object is encoded into an XML node using the following.
The output of the encoding may be viewed using GlobalConfig.logger as follows.
Finally, the result of the encoding looks as follows.
In the above output, the foo and bar fields have been mapped to attributes with the same names, and the name of the constructor was used for the node name.
Booleans
Since booleans are numbers in JavaScript, all boolean values are encoded into 1 for true and 0 for false. The decoder also accepts the string true and false for boolean values.
Objects
The above scheme is applied to all atomic fields, that is, to all non-object fields of an object. For object fields, a child node is created with a special attribute that contains the field name. This special attribute is called "as" and hence, as is a reserved word that should not be used for a field name.
Consider the following example where foo is an object and bar is an atomic property of foo.
This will be mapped to the following XML structure by ObjectCodec.
In the above output, the inner Object node contains the as-attribute that specifies the field name in the enclosing object. That is, the field foo was mapped to a child node with an as-attribute that has the value foo.
Arrays
Arrays are special objects that are either associative, in which case each key, value pair is treated like a field where the key is the field name, or they are a sequence of atomic values and objects, which is mapped to a sequence of child nodes. For object elements, the above scheme is applied without the use of the special as-attribute for creating each child. For atomic elements, a special add-node is created with the value stored in the value-attribute.
For example, the following array contains one atomic value and one object with a field called bar. Furthermore it contains two associative entries called bar with an atomic value, and foo with an object value.
This array is represented by the following XML nodes.
The Array node name is the name of the constructor. The additional as-attribute in the last child contains the key of the associative entry, whereas the second last child is part of the array sequence and does not have an as-attribute.
References
Objects may be represented as child nodes or attributes with ID values, which are used to lookup the object in a table within Codec. The isReference function is in charge of deciding if a specific field should be encoded as a reference or not. Its default implementation returns true if the field name is in idrefs, an array of strings that is used to configure the ObjectCodec.
Using this approach, the mapping does not guarantee that the referenced object itself exists in the document. The fields that are encoded as references must be carefully chosen to make sure all referenced objects exist in the document, or may be resolved by some other means if necessary.
For example, in the case of the graph model all cells are stored in a tree whose root is referenced by the model's root field. A tree is a structure that is well suited for an XML representation, however, the additional edges in the graph model have a reference to a source and target cell, which are also contained in the tree. To handle this case, the source and target cell of an edge are treated as references, whereas the children are treated as objects. Since all cells are contained in the tree and no edge references a source or target outside the tree, this setup makes sure all referenced objects are contained in the document.
In the case of a tree structure we must further avoid infinite recursion by ignoring the parent reference of each child. This is done by returning true in isExcluded, whose default implementation uses the array of excluded fieldnames passed to the ObjectCodec constructor.
References are only used for cells in mxGraph. For defining other referencable object types, the codec must be able to work out the ID of an object. This is done by implementing Codec.reference. For decoding a reference, the XML node with the respective id-attribute is fetched from the document, decoded, and stored in a lookup table for later reference. For looking up external objects, Codec.lookup may be implemented.
Expressions
For decoding JavaScript expressions, the add-node may be used with a text content that contains the JavaScript expression. For example, the following creates a field called foo in the enclosing object and assigns it the value of Constants.ALIGN.LEFT.
The resulting object has a field called foo with the value "left". Its XML representation looks as follows.
This means the expression is evaluated at decoding time and the result of the evaluation is stored in the respective field. Valid expressions are all JavaScript expressions, including function definitions, which are mapped to functions on the resulting object.
Expressions are only evaluated if allowEval is true.