IBM BPM, V8.0.1, All platforms > Programming IBM BPM > Business objects programming > Programming techniques > Use the Sequence object to set data order
Why do I need to know a DataObject has a Sequence?
If you are working on a DataObject that has a Sequence, it is important to know the order in which the data is set. Because of this, care must be taken in the order in which the values are set.
A DataObject that is not sequenced allows random order set access. This functions like a Map where all the keys are set to the same values. It does not matter in what order the keys were set, the data in the map is the same, and would be serialized to XML identically.
When a DataObject is sequenced, the order in which the data was set is recorded in the Sequence, much like adding data to a List. This provides two ways to access the data, by name/value pairs (the DataObject APIs) and by order in which it was set (the Sequence APIs).
You can use the DataObject set(...) or Sequence add(...) APIs to preserve the structure. This ordering affects the way that the XML is serialized.
Take for example, the <all/> tag XSD. When the set methods are called in the following order it produces the following XML when serialized:
DataObject all = ... all.set("element1", "foo"); all.set("element2", "bar"); <?xml version="1.0" encoding="UTF-8"?> <p:All xsi:type="p:All" xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance xmlns:p="http://All"> <element1>foo</element1> <element2>bar</element2> </p:All>If instead, the set methods are called in the opposite order, then the following XML is produced when the business object is serialized:
DataObject all = ... all.set("element2", "bar"); all.set("element1", "foo"); <?xml version="1.0" encoding="UTF-8"?> <p:All xsi:type="p:All" xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance xmlns:p="http://All"> <element2>bar</element2> <element1>foo</element1> </p:All>If the order of the Sequence is ever changed, then the Sequence class has basic add, remove, and move methods to allow the user to alter the order of Sequence.