Glossary

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Attribute

In connection with XML or HTML (or SGML in general), attributes are the named values associated with elements. For example, in <body bgcolor=black text=green>...</body>, the attributes are bgcolor=black and text=green. On the left side of = is the name of the attribute, while on the right side is the value of the attribute. Note that in XML, the values must be quoted (for example: <body bgcolor="black" text='green'>), while in HTML it is optional for certain values.

See Also Start-tag

Environment

An Environment object stores the runtime state of a single template template processing job. That is, for each Template.process(...) call, an Environment instance will be created, and then discarded when process returns. This object stores the set of temporary variables created by the template, the value of settings set by the template, the reference to the data-model root, etc. Everything that is needed to fulfill the template processing job.

Extensible Markup Language

A subset (restricted version) of SGML. This is less powerful than SGML, but it easier to learn and much easier to process with programs. If you are an HTML author: XML documents are similar to HTML documents, but the XML standard doesn't specify the usable elements. XML is a much more general-purpose thing than HTML. For example you can use XML to describe Web pages (like HTML) or to describe non-visual information like a phone book database.

FreeMarker Template Language

Simple programming language designed to write text file templates, especially HTML templates.

FTL

See FreeMarker Template Language

FTL tag

Tag-like text fragment used to invoke FreeMarker directives in FTL templates. These are similar to HTML or XML tags at the first glance. The most prominent difference is that the tag name is started with # or @. Another important difference is that FTL tags do not use attributes, but a substantially different syntax to specify parameters. Examples of FTL tags: <#if newUser>, </#if>, <@menuitem title="Projects" link="projects.html"/>

Full-qualified name

... of nodes (XML node or other FTL node variable): The full-qualified name of a node specifies not only the node name (node?node_name), but also the node namespace (node?node_namespace), this way it unambiguously identify a certain kind of node. The format of the full-qualified name is nodeName or prefix:nodeName. The prefix is shorthand to identify the node namespace (the a node namespace is usually specified with a long ugly URI). In FTL, prefixes are associated with the node namespaces with the ns_prefixes parameter of the ftl directive. In XML files, prefixes are associated with the node namespaces with the xmlns:prefix attributes. The lack of the prefix means that the node uses the default node namespace, if a default node namespace is defined; otherwise it means that the node does not belong to any node namespace. The default node namespace is defined in FTL by registering reserved prefix D with the ns_prefixes parameter of the ftl directive. In XML files it is defined with attribute xmlns.

... of Java classes: The full-qualified name of a Java class contains both the class name and the name of the package the class belongs to. This way it unambiguously specifies the class, regardless of the context. An example of full-qualifed class name: java.util.Map (as opposed to Map).

Function definition body

The template fragment between the <#function ...> and </#function>. This template fragment will be executed when you call the function (for example as myFuction(1, 2)).

Hash

A variable that acts as a container that stores sub variables that can be retrieved via a string that is a lookup name.

See Also Sequence

Line break

Line break is a special character (or a sequence of special characters) that causes a line breaking when you see the text as plain text (say, when you read the text with Windows notepad). Typically you type this character by hitting ENTER or RETURN key. The line break is represented with different characters on different platforms (to cause incompatibility and confusion...): "line feed" character on UNIX-es, "carriage return" character on Macintosh, "carriage return" + "line feed" (two characters!) on Windows and DOS. Note that line breaks in HTML do not have a visual effect when viewed in a browser; you must use markup such as <BR> for that. This manual never means <BR> when it says "line-break".

Macro definition body

The template fragment between the <#macro ...> and </#macro>. This template fragment will be executed when you call the macro (for example as <@myMacro/>).

Markup output value

A value with FTL type "markup output". This type is related to auto-escaping mechanism; you can read about this type there. But in short, this is a value that stores text that's already in the output markup format (like HTML, XML, RTF, etc.), and hence must not be auto-escaped.

Method

A variable that calculates something based on parameters you give, and returns the result.

MVC pattern

MVC stands for Model View Controller. It's a design pattern started his life in the 70's as a framework developer by Trygve Reenskaug for Smalltalk, and was used primary for for UI-s (user interfaces). MVC considers three roles:

Model: Model represents application (domain) specific information in a non-visual way. For example, an array of product objects in the memory of your computer is the part of the model.
View: View displays the model and provides UI. For example, it's the task of the view component to render the array of product objects to a HTML page.
Controller: The controller handles user input, modifies the model, and ensures that the view is updated when needed. For example it is the task of controller to take the incoming HTTP requests, parse the received parameters (forms), dispatch the requests to the proper business logic object, and chose the right template for the HTTP response.

The most important thing for us when applying MVC for Web applications is the separation of View from the other two roles. This allows the separation of designers (HTML authors) from programmers. Designers deal with the visual aspects, programmers deal with the application logic and other technical issues; everybody works on what he is good at. Designers and programmers are less dependent on each other. Designers can change the appearance without programmers having to change or recompile the program.

For more information I recommend reading chapter 4.4 of Designing Enterprise Applications with the J2EE Platform blueprint.

Output encoding

Means output charset. In the Java world the term "encoding" is commonly (mis)used as a synonym to charset.

Parse-time error

An error occurring during the template parsing phase, as opposed to the later template execution phase (see more explanation below). The presence of a such error prevents the execution of the whole template, even if the execution wouldn't use the part where the error is. This is seen as an advantage, as it helps early (before deployment, ideally in-editor) error detection.

A FreeMarker template is processed in two phases. First the whole template is analyzed syntactically, which is called parsing. The result of the parsing is a Template Java object, which is usually cached for fast reuse. Later, the already parsed template can be executed for unlimited times to produce output based on the content of a data-model. Errors occurring during the parsing are called parse-time errors.

Predefined directive

Directive what is defined by FreeMarker, thus always available. Example of predefined directives: if, list, include

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