Trim token

This section explains how to eliminate HTML tag element from HTML page in PageMixer framework. Explanation uses the filter which eliminate "<br>" tags from HTML page.

before line break.<br>
after line break.

before line break.
after line break.

In other words, the filter tirms the tokens named as "br" from sequence.

Overview

Class diagram

Class diagram in this section is shown below:

Class diagram (click for large figure)

Classes which you must define are colored, and other are already defined.

Object diagram

Object diagram in this section is shown below:

Object diagram (click for large figure)

Sequence diagram

Sequence diagram in this section is shown below:

Sequence diagram (click for large figure)

Classe names

In this tutorial, abbreviated class names are used. Complete names are shown below.

Classes of PageMixer framework

Tutorial specific classes

Create TokenWatcher

In PageMixer framework, "processing something" and "finding targets of that" are treated as different functions, and for single token 'filterring', these are implemented by "TokenEditFilter" and "TokenWatcher".

So, at first, create TokenWatcher object to tell TokenEditFilter what token should be trimmed in sequence (= "finding targets of that").

In this case, to trim all token named as "br", "TokenWatcher.Name" is used. It is "Token Watcher watching at Name of it".

new TokenWatcher.Name(HTMLSymbolSet.SET.BR)

To create instance of TokenWatcher.Name class, you should specify "Symbol" on construction, and "HTMLSymbolSet" is used to get Symbol in above example.

It is out of purpose of this tutorial to explain what Symbol is, why Symbol is used instead of String, or other detail about them.

In this tutorial, it is enough that you know how to use HTMLSymbolSet to get Symbol objects appropirated to well-known names of HTML tag and attribute. Please see "Symbol comparison" for detail.

Concretize TokenEditFilter

Then, define derived class from "TokenEditFilter" to trim token found by TokenWatcher defined as above.

"Trimming token from sequence" is to discard the trimmed token without passing it to connected Consumer, so derived class is defined as below.

public class BrTrimFilter
    extends TokenEditFilter
{
    final static
    private HTMLSymbolSet SET = HTMLSymbolSet.SET;

    ///////////////////////////////////////////

    public BrTrimFilter(){
        super(new TokenWatcher.Name(SET.BR));
    }

    ///////////////////////////////////////////
    // Concretization of class TokenEditFilter

    protected void edit(ConsumerContext context,
                        Token token)
    {
        // NOTHING TO DO = DISCARD "BR" TOKEN
    }
}

Connect and mix

Now, everything needed are ready to use. Execution code is as below (see pagemixer.filter.BrTrimFilter for detail).

try{
    Bootstrap bootstrap =
    new Bootstrap.Default(filename);

    // apply the filter
    bootstrap.execute(new BrTrimFilter());
}
catch(Exception e){
    e.printStackTrace(System.err);
}

Sample HTML file as input is "index.en.html" under "src/demo/servlet/war/WEB-INF/page/demosite" in distribution.