fr.gedeon.telnetservice
Class OutputFormatVelocityImpl

java.lang.Object
  fr.gedeon.telnetservice.OutputFormatDefaultImpl
      fr.gedeon.telnetservice.OutputFormatVT100Impl
          fr.gedeon.telnetservice.OutputFormatVelocityImpl

All Implemented Interfaces:

OutputFormat, OutputFormatSpi, OutputFormatVT100Constants

public abstract class OutputFormatVelocityImpl
extends OutputFormatVT100Impl

This implementation of the OutputFormat interface formats a given subject using a selected Apache Velocity Engine template. For more information on the Apache Velocity Engine and the Apache Software Foundation, please refer to the 'See Also' section below.

The template selection process is based on the class structure of the subject to be represented. This class is abstract but does not require any method implementation, the extension mechanism is used to provide bundle specific templates as follows:
If a class custompackage.MyOutputFormatVelocityImpl extends OutputFormatVelocityImpl, the templates that are provided by this class are located under: custompackage/vms/ in the custom bundle's domain. Subject classes or interfaces that require a template must have a template in that location, the template for a class or interface would be named: [package].[classname].vm. For example, the template for java.util.List.class in the above situation would be named in: custompackage/vms/java.util.List.vm

The search order is as follows:

1. The subject class is checked
2. The subject interfaces are checked in the order they are provided by the class definition, this order is described here
3. The process is repeated with the subject's superclass

When a template is found, it is cached against all the classes and interfaces that were visited to arrive to it, and when a lookup fails for a class that class is cached as a failed lookup class. The caches are checked before a lengthy search operation to improve performance.
If a different template source is to be used, it is strongly recommended to override findClassTemplate(Package, Class), this would allow to load the templates from a different location while still having the caching mechanism. The same Package/Class pair will not be requested twice.

The template is merged with the following context entries:

• sessionState: contains the current session state handle
• format: is an instance of the global output format (sessionState.getSession().getOutputFormat()
• vt100: a tool to provide syntax coloring
• subject: the subject to represent
• indent: the indent suggested by the caller of the format method.

Please be sure to read VTL (Velocity Template Language) documentation to write a template.

The following is an example template, this one is for java.lang.Iterable:

 #foreach ( $item in $subject )
 $indent  o $format.format($sessionState, $item, "${indent}    ")
 #end
 

The template lays each item in the iterable each on a new line, and puts an indent and a bullet before it. However, it doesnt impose a format on the item, it delegates the item's representation back to the format search engine.
Replacing the o in the above with ${format.style( [ $vt100.ATTRS_FORE_RED ])}o${format.style( [ ] )} would make the bullet plain red on black background.
$format.style() takes an array of color attributes, those correspond to the STYLE_* and ATTRS_* constants declared in OutputFormatVT100Constants. It is important to reset the style once it's no longer wanted (by having a ${format.style( [ ] )} that matches each ${format.style( [ $vt100.ATTRS_FORE_RED ])} to avoid colors running out of the subject's boundaries.

Author:

wgedeon@gmail.com

See Also:

OutputFormatVT100Constants, Apache Velocity Engine site, Apache Software Foundation site

Field Summary

Fields inherited from interface fr.gedeon.telnetservice.OutputFormatVT100Constants

_DONE, _MORE, _RESET, ATTRS_BACK_BLACK, ATTRS_BACK_BLUE, ATTRS_BACK_CYAN, ATTRS_BACK_GREEN, ATTRS_BACK_MAGENTA, ATTRS_BACK_RED, ATTRS_BACK_WHITE, ATTRS_BACK_YELLOW, ATTRS_DEFAULT, ATTRS_FORE_BLACK, ATTRS_FORE_BLUE, ATTRS_FORE_CYAN, ATTRS_FORE_GREEN, ATTRS_FORE_MAGENTA, ATTRS_FORE_RED, ATTRS_FORE_WHITE, ATTRS_FORE_YELLOW, STYLE_BLINK, STYLE_BOLD, STYLE_DIM, STYLE_HIDDEN, STYLE_REVERSE, STYLE_UNDERSCORE

Constructor Summary

OutputFormatVelocityImpl()


Method Summary

protected org.apache.velocity.Template	findClassTemplate(Package base, Class clazz)
StringBuffer	format(SessionState sessionState, StringBuffer buffer, Object subject, String indent) Uses the velocity template associated with the given subject to append this subject's representation to the buffer. The template is given the following context: outputFormat holds this instance, subject the subject to be represented, and indent the suggested indent to affect each lined
boolean	formats(Object subject) Called to check if the implementation of this interface knows how to format the given subject.
String	toString()

Methods inherited from class fr.gedeon.telnetservice.OutputFormatVT100Impl

resetAttrs, resetAttrs, setAttrs, setAttrs, setAttrs, setAttrs, style, style

Methods inherited from class fr.gedeon.telnetservice.OutputFormatDefaultImpl

format, format, format, getPriority

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface fr.gedeon.telnetservice.OutputFormatSpi

getPriority

Methods inherited from interface fr.gedeon.telnetservice.OutputFormat

format, format, format

Constructor Detail

OutputFormatVelocityImpl

public OutputFormatVelocityImpl()

Method Detail

findClassTemplate

protected org.apache.velocity.Template findClassTemplate(Package base,
                                                         Class clazz)

formats

public boolean formats(Object subject)

Description copied from interface: OutputFormatSpi

Called to check if the implementation of this interface knows how to format the given subject.

Specified by:

formats in interface OutputFormatSpi

Overrides:

formats in class OutputFormatDefaultImpl

Returns:

true

format

public StringBuffer format(SessionState sessionState,
                           StringBuffer buffer,
                           Object subject,
                           String indent)
                    throws OutputFormatException

Uses the velocity template associated with the given subject to append this subject's representation to the buffer.
The template is given the following context:

• outputFormat holds this instance,
• subject the subject to be represented, and
• indent the suggested indent to affect each lined

Specified by:

format in interface OutputFormat

Overrides:

format in class OutputFormatDefaultImpl

Parameters:

sessionState - the current session state

buffer - the caller's current buffer

subject - the subject to be represented

indent - a hint to the indent expected by the caller at the beginning of each line.

Returns:

the provided buffer updated with the subject's representation

Throws:

OutputFormatException - for any errors that occur in the formatting process.

toString

public String toString()

Overrides:

toString in class Object