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Developing components, Understanding component design, Best practices for component design

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Developing components 70 Developing components Understanding component design A typical component contains four classes: • Service interface-This defines the contracts for the service implementation class and serves as a property type for the bean implementation class. • Service implementation-This implements service interface class. • Bean interface-This sets properties for the bean implementation class. • Bean implementation-This implements the bean interface and calls the methods of the service implementation class. Best practices for component design • Implement a standard JavaScript component interface: - Implement the new operator to create instances of the component. - Use uppercase letters for constants. - Define all constants as children of the component class. - Implement the setInput method, and accept an array where appropriate. - Implement the result field, and return an array where appropriate. • Each method is automatically logged to the confirmation page when called. Use com.lexmark.workflow.framework.annotation.ConfirmBeanMethodLoggingOverride to hide methods or arguments that should not appear in the confirmation page, such as passwords: - To prevent a method from appearing at all on the confirmation page, add @ConfirmBeanMethodLoggingOverride(hide=true) before the method declaration. - To prevent only the arguments of a method from appearing on the confirmation page, add @ConfirmBeanMethodLoggingOverride(hideArguments=true) before the method declaration. The arguments are replaced with the text on the confirmation page. • Log all activity using the Apache log4j framework, using the following levels: - ERROR-Fatal errors, such as system failures - WARN-Non‑fatal errors, such as script exceptions - INFO-Diagnostic information, such as progress or status - DEBUG-Debugging information • Handle script errors by throwing exceptions. Avoid catching exceptions within the component. • Use com.lexmark.workflow.framework.service.temporaryFile.TemporaryFileService for output files and temporary files. • Add a new bean, xxxVersionBean, in applicationContext.xml to show the version number of the component in LMC.

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Developing components
Understanding component design
A typical component contains four classes:
•
Service interface
—This defines the contracts for the service implementation class and serves as a property type
for the bean implementation class.
•
Service implementation
—This implements service interface class.
•
Bean interface
—This sets properties for the bean implementation class.
•
Bean implementation
—This implements the bean interface and calls the methods of the service implementation
class.
Best practices for component design
•
Implement a standard JavaScript component interface:
–
Implement the
new
operator to create instances of the component.
–
Use uppercase letters for constants.
–
Define all constants as children of the component class.
–
Implement the
setInput
method, and accept an array where appropriate.
–
Implement the
result
field, and return an array where appropriate.
•
Each method is automatically logged to the confirmation page when called. Use
com.lexmark.workflow.framework.annotation.ConfirmBeanMethodLoggingOverride
to
hide methods or arguments that should not appear in the confirmation page, such as passwords:
–
To prevent a method from appearing at all on the confirmation page, add
@ConfirmBeanMethodLoggingOverride(hide=true)
before the method declaration.
–
To prevent only the arguments of a method from appearing on the confirmation page, add
@ConfirmBeanMethodLoggingOverride(hideArguments=true)
before the method declaration.
The arguments are replaced with the text
<hidden
‑
args>
on the confirmation page.
•
Log all activity using the Apache log4j framework, using the following levels:
–
ERROR
—Fatal errors, such as system failures
–
WARN
—Non
‑
fatal errors, such as script exceptions
–
INFO
—Diagnostic information, such as progress or status
–
DEBUG
—Debugging information
•
Handle script errors by throwing exceptions. Avoid catching exceptions within the component.
•
Use
com.lexmark.workflow.framework.service.temporaryFile.TemporaryFileService
for output files and temporary files.
•
Add a new bean,
xxxVersionBean
, in applicationContext.xml to show the version number of the component in
LMC.
Developing components
70