Creating Attributes
Defining an attribute.
An xchain attribute is defined including an abstract method in a command and annotating it with the Attribute annotation. The method should have one parameter of type JXPathContext and may throw an exception. Here is an example of an attribute definition:
@Attribute(localName="name", type=AttributeType.JXPATH_VALUE) public static String getName( JXPathContext context );
This example defines a name attribute on the current XChain command. The value of that attribute will be treated as a jxpath, so calling:
String name = getName(context);
from inside a command that had the attribute:
<commnd name="$name"/>
will return the value of the name variable. If the name attribute is not defined, or the jxpath caused an exception to be thrown, then null will be returned.
The type attribute and its effect of the attribute.
An Attribute annotation has a type attribute that tells XChains how to convert the attribute in the xml into a java object. Each AttributeType cause the value of the xml attribute to be treated differently. Some will treat the value as an xpath, others will treat it as a literal value. This section defines the attribute types, they kind of code the produce, and the valid return types that they support.
AttributeType.ATTRIBUTE_VALUE_TEMPLATE
The attribute value template type treats the value as an attribute value template, much like attribute value templates in xslt. The value is a literal, except inside {} areas that contain jxpaths. The literal parts and jxpath parts are concatinated into a string and converted into the return type. You can escape { and } by doubling them in the value.
Currently this attribute type only supports String and Enum types, but others will be supported in the future.
A command with the attribute:
@Attribute(localName="name", type=AttributeType.ATTRIBUTE_VALUE_TEMPLATE) public static String getName( JXPathContext context );
And the variable $var defined as "value" in the context, will resolve to the following values:
| Attribute | getName(JXPathContext) |
| name="name" | "name" |
| name="$var" | "$var" |
| name="{$var}" | "value" |
| name="name {$var}" | "name value" |
| name="name {{$var}}" | "name {$var}" |