HiveMind Module Descriptor

<attribute> is used to define an attribute within an <element>. Inside a <contribution>, only known attributes are allowed in elements; unknown attributes will be logged as an error and ignored. In addition, some attributes are required; again, errors occur if the contributed element does not provide a value for the attribute.

The <configuration-point> element defines a configuration extension point.

Contains: <schema>

<configuration-point> only defines a configuration point, it does not supply any data into that point. The <contribution> element is used to provide such data.

The <contribution> element contributes elements to an existing configuration extension point.

The content of the <contribution> consists of elements. These elements are converted, in accordance with the configuration point's <schema>, into Java objects.

<conversion> is an alternative to <rules> that is generally simpler and more concise. An <element> should contain <conversion> or <rules> but not both.

<conversion> is geared towards the typical case; a straight-forward mapping of the element to an instance of a Java class, and a mapping of the element's attributes to the properties of the Java object.

Contains: <map>

Each attribute will be mapped to a property. A limited amount of name mangling occurs: if the attribute name contains dashes, they are removed, and the character following is converted to upper case. So, an attribute named "complex-attribute-name" would be mapped to a property named "complexAttributeName". Only attributes identified with a <attribute> element will be mapped, others will be ignored.

<create-instance> is used, within <service-point> and <implementation> to create the core service implementation for a service by instantiating a class. This is appropriate for simple services that require no explicit configuration.

Additional service models can be defined via the hivemind.ServiceModels configuration point.

The <element> element is used to define an element in a the <schema>. <element> may also be nested within another <element>, to indicate an element that may be enclosed within another element.

Contains: <attribute>, <conversion>, <element>, <rules>

Future enhancements to the HiveMind framework will include greater sophistication in defining configuration content.

The <implementation> element contributes a core implementation or interceptors to a service extension point.

Contains: <create-instance>, <interceptor>, <invoke-factory>

<interceptor> contributes an interceptor factory to a service extension point. An interceptor factory is a service which implements the ServiceInterceptorFactory interface.

When the service is constructed, each invoked interceptor factory will fabricate an interceptor class to provide additional functionality for the service.

Like a service implementation factory, a service interceptor factory may need parameters. As with <invoke-factory>, parameters to the interceptor factory are enclosed by the <interceptor> element. The service interceptor factory will decode the parameters using the schema identified by its parameters-schema-id attribute.

Interceptor ordering is based on dependencies; each interceptor can identify, by interceptor service id, other interceptors. Interceptors in the before list are deferred until after this interceptor. Likewise, this interceptor is deferred until after all interceptors in the after list.

The value for before or after is a list of service ids seperated by commas. Service ids may be unqualified if they are within the same module. Alternately, the fixed value * may be used instead of a list: this indicates that the interceptor should be ordered absolutely first or absolutely last.

The <invoke-factory> element is used to provide a service implementation for a service by invoking another service, a factory service.

A service factory defines its parameters in terms of a schema. The content of the <invoke-factory> is converted, in accordance with the factory's schema, and provided to the factory.

The <map> element appears within <conversion> to override the default mapping from an attribute to a property. By default, the property name is expected to match the attribute name (with the name mangling described in the description of <conversion>); the <map> element is used to handle exceptions to the rule.

The <module> element is the root element.

Contains: <contribution>, <configuration-point>, <implementation> , <service-point>, <schema>, <sub-module>

The <parameters-schema> element is identical to the <schema> element, but only appears inside <service-point>, to define the schema for the parameters for a service implementation factory or service interceptor factory.

<rules> is a container for element and attribute parsing rules within an <element>. These rules are responsible for converting the contributed element and its attributes into objects and object properties. The available rules are documented separately .

The <schema> element is used to describe the format of element contributions to an <configuration-point>, or parameters provided to a service or interceptor factory.

Contains: <element>

At a future time, the <schema> element will be extended to provide more options, to provide more precise control over the elements that may be provided in an <contribution>. At this time, a <schema> is simply a list of <element> elements.

The <service-point> element defines a service extension point.

Contains: <create-instance>, <interceptor>, <invoke-factory> , <parameters-schema>

The <sub-module> element is used to identify an additional HiveMind module deployment descriptor. This is used when a single JAR file contains logically distinct packages, each of which should be treated as an individual HiveMind module. This can also be useful as a way to reduce developer conflict against a single, large, central module descriptor by effectively breaking it into smaller pieces. Sub-modules identified in this way must still have their own unique module id.

The descriptor should be specified as a relative path, either the name of another module descriptor within the same folder, or within a child folder.