# CycleStrategy
Date: 2013-02-18

## org.simpleframework.xml.strategy
Class CycleStrategy

    java.lang.Object
      org.simpleframework.xml.strategy.CycleStrategy

All Implemented Interfaces:
  Strategy

    public class CycleStrategy

extends java.lang.Object
implements Strategy

The `CycleStrategy` represents a strategy that is used to augment the deserialization and serialization process such that cycles in an object graph can be supported. This adds additional attributes to the serialized XML elements so that during the deserialization process an objects cycles can be created. Without the use of a strategy such as this, cycles could cause an infinite loop during the serialization process while traversing the graph.

        <root id="1">
           <object id="2">
              <object id="3" name="name">Example</item>
              <object reference="2"/>
           </object>
        </root>

In the above serialized XML there is a circular reference, where the XML element with id "2" contains a reference to itself. In most data binding frameworks this will cause an infinite loop, or in some cases will just fail to represent the references well. With this strategy you can ensure that cycles in complex object graphs will be maintained and can be serialized safely.

Author:
  Niall Gallagher
See Also:
  `Persister`, `Strategy`

Constructor Summary
`CycleStrategy()` Constructor for the `CycleStrategy` object.
`CycleStrategy(java.lang.String mark, java.lang.String refer)` Constructor for the `CycleStrategy` object.
`CycleStrategy(java.lang.String mark, java.lang.String refer, java.lang.String label)` Constructor for the `CycleStrategy` object.
`CycleStrategy(java.lang.String mark, java.lang.String refer, java.lang.String label, java.lang.String length)` Constructor for the `CycleStrategy` object.

Method Summary
`Value` `read(Type type, NodeMap node, java.util.Map map)` This method is used to read an object from the specified node.
`boolean` `write(Type type, java.lang.Object value, NodeMap node, java.util.Map map)` This is used to write the reference in to the XML element that is to be written.

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

Constructor Detail

### CycleStrategy

    public CycleStrategy()

  Constructor for the `CycleStrategy` object. This is used to create a strategy with default values. By default the values used are "id" and "reference". These values will be added to XML elements during the serialization process. And will be used to deserialize the object cycles fully.

### CycleStrategy

    public CycleStrategy(java.lang.String mark,
                         java.lang.String refer)

  Constructor for the `CycleStrategy` object. This is used to create a strategy with the specified attributes, which will be added to serialized XML elements. These attributes are used to serialize the objects in such a way the cycles in the object graph can be deserialized and used fully.

  Parameters:
    `mark` - this is used to mark the identity of an object
    `refer` - this is used to refer to an existing object

### CycleStrategy

    public CycleStrategy(java.lang.String mark,
                         java.lang.String refer,
                         java.lang.String label)

  Constructor for the `CycleStrategy` object. This is used to create a strategy with the specified attributes, which will be added to serialized XML elements. These attributes are used to serialize the objects in such a way the cycles in the object graph can be deserialized and used fully.

  Parameters:
    `mark` - this is used to mark the identity of an object
    `refer` - this is used to refer to an existing object
    `label` - this is used to specify the class for the field

### CycleStrategy

    public CycleStrategy(java.lang.String mark,
                         java.lang.String refer,
                         java.lang.String label,
                         java.lang.String length)

  Constructor for the `CycleStrategy` object. This is used to create a strategy with the specified attributes, which will be added to serialized XML elements. These attributes are used to serialize the objects in such a way the cycles in the object graph can be deserialized and used fully.

  Parameters:
    `mark` - this is used to mark the identity of an object
    `refer` - this is used to refer to an existing object
    `label` - this is used to specify the class for the field
    `length` - this is the length attribute used for arrays

Method Detail

### read

    public Value read(Type type,
                      NodeMap node,
                      java.util.Map map)
               throws java.lang.Exception

  This method is used to read an object from the specified node. In order to get the root type the field and node map are specified. The field represents the annotated method or field within the deserialized object. The node map is used to get the attributes used to describe the objects identity, or in the case of an existing object it contains an object reference.

  Specified by:
    `read` in interface `Strategy`
  Parameters:
    `type` - the method or field in the deserialized object
    `node` - this is the XML element attributes to read
    `map` - this is the session map used for deserialization
  Returns:
    this returns an instance to insert into the object
  Throws:
    `java.lang.Exception` - thrown if the class cannot be resolved

### write

    public boolean write(Type type,
                         java.lang.Object value,
                         NodeMap node,
                         java.util.Map map)

  This is used to write the reference in to the XML element that is to be written. This will either insert an object identity if the object has not previously been written, or, if the object has already been written in a previous element, this will write the reference to that object. This allows all cycles within the graph to be serialized so that they can be fully deserialized.

  Specified by:
    `write` in interface `Strategy`
  Parameters:
    `type` - the type of the field or method in the object
    `value` - this is the actual object that is to be written
    `node` - this is the XML element attribute map to use
    `map` - this is the session map used for the serialization
  Returns:
    returns true if the object has been fully serialized