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Presentation of Data
The rest of the article is about how data is presented and formatted in a nice, readable way. This zip file contains a class, DocObject, with a static toString method that follows the ideas outlined above. The basic format of the data returned by DocObject.toString is this:
package-and-classname{
fieldname=value
fieldname=value
. . .
}
Since fields often are other classes, the format will generally look like this:
package-and-classname{
fieldname=value
fieldname=package-and-classname{
fieldname=value
fieldname=value
. . .
}
. . .
}
The format of the DocObject.toString method is controlled by set of options:
| Option |
Purpose |
| showSuperClass |
true/false: determines if a class' superclasses should be
included in the data returned. |
| indentationString |
String: the string used to indent fieldnames in a class (4 spaces in the
examples above) |
classOpenBracket
classCloseBracket |
The strings used to mark the opening and closing of a class.
Default: { and } |
arrayOpenBracket
arrayCloseBracket |
The strings used to enclose elements in an array.
Default: [ and ] |
collectionOpenBracket
collectionCloseBracket |
The strings used to mark the opening and closing of a collection.
Default: [ and ] |
mapOpenBracket
mapCloseBracket |
The strings used to mark the opening and closing of a map.
Default: { and } |
HTML Format
When debugging Web applications, it can be useful to show the results from DocObject.toString in HTML format. The simple solution, HTML-wise, is to put the data inside a pair of <PRE> tags, but you can do much better than this. For a large output, it's very convenient to be able to "collapse" or "expand" the data belonging to a class. Using the last example above, a series of expansions looks like this:
To implement this, you need to:
- Put all the data from one class (from the "{" to the "}") inside a
<DIV> tag.
- Set a named style sheet on this tag.
- Create a link on the "package-and-class" name that invokes a JavaScript function, which flips the visibility on the
<DIV> tag between "visible" and "invisible."
- Let this JavaScript function also switch the "plus" and "minus" image in front of the link.
You can see the complete HTML-page here.
An example of how to use this HTML setup could be to display the contents of the servlet "request" and "session" objects. You may read more details about extracting information from these objects in "Development
Standards in Apache Struts".
Simple and Useful
Adding toString methods to your classes often makes development and debugging much simpler. Generally speaking, toString is useful in any situation where a complete picture of the state of a class is needed, for example, when documenting a systems error to a log. The generic solution presented above keeps the coding and maintenance of toString methods to a minimum.
Related Resources
- All the programs and files from the article are in this zip file.
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