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## com.mxgraph.io
Class mxCodec

    java.lang.Object
      com.mxgraph.io.mxCodec

    public class mxCodec

extends Object

XML codec for Java object graphs. In order to resolve forward references when reading files the XML document that contains the data must be passed to the constructor.

Field Summary
`protected Document` | `document` Holds the owner document of the codec.
`protected boolean` | `encodeDefaults` Specifies if default values should be encoded.
`protected Map<String,Object>` | `objects` Maps from IDs to objects.

Constructor Summary
`mxCodec()` Constructs an XML encoder/decoder with a new owner document.
`mxCodec(Document document)` Constructs an XML encoder/decoder for the specified owner document.

Method Summary
`Object` | `decode(Node node)` Decodes the given XML node using `decode(Node, Object)`.
`Object` | `decode(Node node, Object into)` Decodes the given XML node.
`mxICell` | `decodeCell(Node node, boolean restoreStructures)` Decodes cells that have been encoded using inversion, ie.
`Node` | `encode(Object obj)` Encodes the specified object and returns the resulting XML node.
`void` | `encodeCell(mxICell cell, Node node, boolean includeChildren)` Encoding of cell hierarchies is built-into the core, but is a higher-level function that needs to be explicitely used by the respective object encoders (eg.
`Document` | `getDocument()` Returns the owner document of the codec.
`Node` | `getElementById(String id)` Returns the element with the given ID from the document.
`Node` | `getElementById(String id, String attr)` Returns the element with the given ID from document.
`String` | `getId(Object obj)` Returns the ID of the specified object.
`Object` | `getObject(String id)` Returns the decoded object for the element with the specified ID in `document`.
`Map<String,Object>` | `getObjects()` Returns the object lookup table.
`boolean` | `isEncodeDefaults()` Returns if default values of member variables should be encoded.
`Object` | `lookup(String id)` Hook for subclassers to implement a custom lookup mechanism for cell IDs.
`Object` | `putObject(String id, Object object)` Assoiates the given object with the given ID.
`String` | `reference(Object obj)` Hook for subclassers to implement a custom method for retrieving IDs from objects.
`static void` | `setAttribute(Node node, String attribute, Object value)` Sets the attribute on the specified node to value.
`void` | `setEncodeDefaults(boolean encodeDefaults)` Sets if default values of member variables should be encoded.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### document

    protected Document document

  Holds the owner document of the codec.

### objects

    protected Map<String,Object> objects

  Maps from IDs to objects.

### encodeDefaults

    protected boolean encodeDefaults

  Specifies if default values should be encoded. Default is false.

Constructor Detail

### mxCodec

    public mxCodec()

  Constructs an XML encoder/decoder with a new owner document.

### mxCodec

    public mxCodec(Document document)

  Constructs an XML encoder/decoder for the specified owner document.

  Parameters:
    `document` - Optional XML document that contains the data. If no document is specified then a new document is created using mxUtils.createDocument

Method Detail

### isEncodeDefaults

    public boolean isEncodeDefaults()

  Returns if default values of member variables should be encoded.

### setEncodeDefaults

    public void setEncodeDefaults(boolean encodeDefaults)

  Sets if default values of member variables should be encoded.

### getObjects

    public Map<String,Object> getObjects()

  Returns the object lookup table.

### getDocument

    public Document getDocument()

  Returns the owner document of the codec.

  Returns:
    Returns the owner document.

### putObject

    public Object putObject(String id,
                            Object object)

  Assoiates the given object with the given ID.

  Parameters:
    `id` - ID for the object to be associated with.
    `object` - Object to be associated with the ID.
  Returns:
    Returns the given object.

### getObject

    public Object getObject(String id)

  Returns the decoded object for the element with the specified ID in `document`. If the object is not known then `lookup(String)` is used to find an object. If no object is found, then the element with the respective ID from the document is parsed using `decode(Node)`.

  Parameters:
    `id` - ID of the object to be returned.
  Returns:
    Returns the object for the given ID.

### lookup

    public Object lookup(String id)

  Hook for subclassers to implement a custom lookup mechanism for cell IDs. This implementation always returns null.

  Parameters:
    `id` - ID of the object to be returned.
  Returns:
    Returns the object for the given ID.

### getElementById

    public Node getElementById(String id)

  Returns the element with the given ID from the document.

  Parameters:
    `id` - ID of the element to be returned.
  Returns:
    Returns the element for the given ID.

### getElementById

    public Node getElementById(String id,
                               String attr)

  Returns the element with the given ID from document. The optional attr argument specifies the name of the ID attribute. Default is "id". The XPath expression used to find the element is //*[@attr='arg'] where attr is the name of the ID attribute and arg is the given id. Parameters: id - String that contains the ID. attr - Optional string for the attributename. Default is id.

### getId

    public String getId(Object obj)

  Returns the ID of the specified object. This implementation calls reference first and if that returns null handles the object as an mxCell by returning their IDs using mxCell.getId. If no ID exists for the given cell, then an on-the-fly ID is generated using mxCellPath.create.

  Parameters:
    `obj` - Object to return the ID for.
  Returns:
    Returns the ID for the given object.

### reference

    public String reference(Object obj)

  Hook for subclassers to implement a custom method for retrieving IDs from objects. This implementation always returns null.

  Parameters:
    `obj` - Object whose ID should be returned.
  Returns:
    Returns the ID for the given object.

### encode

    public Node encode(Object obj)

  Encodes the specified object and returns the resulting XML node.

  Parameters:
    `obj` - Object to be encoded.
  Returns:
    Returns an XML node that represents the given object.

### decode

    public Object decode(Node node)

  Decodes the given XML node using `decode(Node, Object)`.

  Parameters:
    `node` - XML node to be decoded.
  Returns:
    Returns an object that represents the given node.

### decode

    public Object decode(Node node,
                         Object into)

  Decodes the given XML node. The optional "into" argument specifies an existing object to be used. If no object is given, then a new instance is created using the constructor from the codec. The function returns the passed in object or the new instance if no object was given.

  Parameters:
    `node` - XML node to be decoded.
    `into` - Optional object to be decodec into.
  Returns:
    Returns an object that represents the given node.

### encodeCell

    public void encodeCell(mxICell cell,
                           Node node,
                           boolean includeChildren)

  Encoding of cell hierarchies is built-into the core, but is a higher-level function that needs to be explicitely used by the respective object encoders (eg. mxModelCodec, mxChildChangeCodec and mxRootChangeCodec). This implementation writes the given cell and its children as a (flat) sequence into the given node. The children are not encoded if the optional includeChildren is false. The function is in charge of adding the result into the given node and has no return value.

  Parameters:
    `cell` - mxCell to be encoded.
    `node` - Parent XML node to add the encoded cell into.
    `includeChildren` - Boolean indicating if the method should include all descendents.

### decodeCell

    public mxICell decodeCell(Node node,
                              boolean restoreStructures)

  Decodes cells that have been encoded using inversion, ie. where the user object is the enclosing node in the XML, and restores the group and graph structure in the cells. Returns a new instance that represents the given node.

  Parameters:
    `node` - XML node that contains the cell data.
    `restoreStructures` - Boolean indicating whether the graph structure should be restored by calling insert and insertEdge on the parent and terminals, respectively.
  Returns:
    Graph cell that represents the given node.

### setAttribute

    public static void setAttribute(Node node,
                                    String attribute,
                                    Object value)

  Sets the attribute on the specified node to value. This is a helper method that makes sure the attribute and value arguments are not null.

  Parameters:
    `node` - XML node to set the attribute for.
    `attribute` - Name of the attribute whose value should be set.
    `value` - New value of the attribute.

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Copyright (c) 2010 Gaudenz Alder. All rights reserved.