Download PDF (1.3 MB) - IBM Redbooks

3.2.4 Business object parsing mode considerations
This section describes how and why to choose the BO parsing mode. Two options for this
mode exist: eager parsing mode and lazy parsing mode.
Overview
WebSphere Business Process Manager V7.0.0.1 introduced BO lazy parsing mode. In this
mode, when BOs are created. their properties are not populated until they are accessed by
the application. Also, when reading XML input, the stream is incrementally parsed and its
properties do not materialize until they are accessed.
In contrast, with eager parsing mode, the input XML stream is immediately and fully parsed
(with some exceptions for specific mediation primitives) and materializes into a complete
in-memory data object representation.
Lazy parsing uses the XML Cursor Interface (XCI) implementation of Service Data Objects
(SDOs), provided by the WebSphere Application Server Feature Pack for Service Component
Architecture (SCA), which is delivered as part of Business Process Manager V8.0. In this
mode, the input XML stream remains in memory throughout the lifetime of the corresponding
BO. The cursor-based XML parser creates nodes in memory only when the nodes are
traversed. Properties and attributes are evaluated only when the application requests them.
Parsing the XML stream in this fashion delivers better performance than complete parsing for
many applications in eager mode. This improvement is especially evident if only a small
portion of the BO is accessed during the application execution.
Lazy parsing also reuses the XML stream when BOs are serialized, for example, for outbound
service calls. The result is faster serialization because serializing the entire in-memory BO
into XML strings is not necessary. Lazy parsing automatically detects namespaces in the
output stream that differ from the namespaces in the original input stream, and corrects them.
This form of serialization is used for all bindings and internal Business Process Manager
runtime components, such as the Business Process Choreographer (BPC) container, and
when custom code calls BO serialization.
To further optimize performance, lazy parsing also employs a technology referred to as
copy-on-write, where properties in BOs are lazily copied. When the copy operation initially
takes place, the target BO points only to the node tree of the source BO. Lazy parsing copies
no properties. Subsequent modifications of either the source or target BO trigger a split of the
affected node in the BO tree, copying BO properties only as needed. Modifications occur in
the local copy of the corresponding node. Copy-on-write is transparent to the application.
Setting parsing mode
In Business Process Manager V8.0, the default parsing mode is the lazy mode for newly
developed applications in Integration Designer V8.0. Applications moved from WebSphere
Process Server V7.0.0.3 and earlier releases continue to run in the eager parsing mode.
However, for these older applications, you can manually enable lazy parsing mode through
Integration Designer, which provides a property for each module and library to configure the
XML parsing mode to either eager or lazy.
Figure 3-5 on page 31 shows the Integration Designer panel that the system displays during
creation of a library. At this point, you can specify whether it can be included in an eager
parsing or lazy parsing module, or both. The default is set to lazy parsing when the library is
initially created. When both parsing modes are selected for the library, the module in which
the library is located determines the actual parsing mode at run time.
30 IBM Business Process Manager V8.0 Performance Tuning and Best Practices