Extensions¶
Creating New Functions for Regular Expressions¶
It is possible to create new functions to use in the link and rewriting filters used by the WebBot crawling module.
To create new functions in WebBot, implemented in Java, the following class has to be extended:
com.denodo.aracne.webbot.util.processors.function.FunctionExpression
implementing its two abstract methods:
public abstract void validate()
which checks that the parameters of the function are valid and, in
another case, launches an ExpressionProcessorException
.
and
public abstract String doProcess()
which evaluates the function and returns the result. In the case of the
built-in DateFormat
function, doProcess
calculates the date
corresponding to a specific expression and returns it as a string
following the indicated pattern.
The FunctionExpression
class provides two utility methods:
public String getParameter(int i) throws InvalidParameterException
public int getNumOfParameters()
which allow obtaining the parameters of the function and its number.
In order for the new functions to be used by Denodo Aracne, these must
belong to the package
com.denodo.aracne.webbot.util.processors.function
.
For more information consult the Denodo Aracne Javadoc documentation and
the examples in <DENODO_HOME>/samples/arn/webbot-api
.