+1 for all :-) > -----Original Message----- > From: craigmcc@localhost [mailto:craigmcc@localhost] On Behalf Of Craig R. > McClanahan > Sent: 15 December 2001 21:26 > To: [EMAIL PROTECTED] > Subject: [Design Discussion] DynaBean - JavaBeans with dynamic properties > > There's been a lot of interest, both here (COMMONS-DEV), on the Struts > mailing lists, and elsewhere in the idea of a JavaBean-like thing where > the set of properties can be dynamically defined. If support for this was > integrated into the BeanUtils package in Commons, we could also make the > methods in BeanUtils and PropertyUtils treat the properties of these beans > like they do for regular JavaBeans, and thus be able to leverage them in > environments based on BeanUtils (such as Struts). > > The purpose of this email is to summarize a set of design requirements for > discussion purposes, so we can coalesce on a design and then get it > implemented. For extra fun, I've thrown in a very-raw idea of what the > APIs might look like -- but I'd like to have the group's agreement before > turning that into code. > > Before embarking on the actual development of dynamic beans support, we > should also do a release of BeanUtils with the current enhancements, to > provide a stable starting point. > > Please let me know what you think! > > > BACKGROUND: > > The purpose of the DynaBean design (I'm not firmly attached to the name, > but kinda like it :-) is to support application programming designs based > on JavaBeans design patterns, but where the static nature of JavaBeans > themselves (i.e. the fact that the set of properties is fixed at compile > time) is too restrictive. Some typical use cases for such a capability: > > * A bean object that represents a Row from a JDBC ResultSet > (the names and types of the column properties cannot be known > in advance because they are based on the SELECT statement). > > * A way to construct and use "value objects" that extract the > properties of an EJB into a structure that can be utilized by a > presentation tier technology such as JSP pages, without having > to hand code the value object. > > * A way to capture *all* of the request parameters from a servlet > request as a single object. > > * A way to dynamically represnt XML input data as a tree of Java objects. > > > DESIGN REQUIREMENTS: > > * Support a completely arbitrary set of properties and corresponding > values, with the ability to add and remove properties dynamically. > > * Support the ability to dynamically register the set of property > names that are allowed, and then enforce storing only those > property names. > > * Support the ability to register data types (Java classes) for each > property, along with the names, with automatic type checking. > > * Support for properties with scalar types, array types, and > "mapped" types (as currently supported in Beanutils). > > * Support "simple" and "indexed" property getters and setters > in a style similar to standard JavaBeans. > > * Support registration of property change listeners and broadcast > of property change events > > * Provide the basic DynaBean API as a Java interface, as well as a > convenience base class, so that applications can adopt it however > they wish. > > * Base implementation class should implement Serializable so that > DynaBeans can be serialized and deserialized (assuming that the > actual property values can be). > > * Transparently support DynaBean objects in the existing BeanUtils > and PropertyUtils classes of the Bean Utilities package. > > * To the maximum extent feasible, provide JavaBeans-like introspection > capabilities of the available properties. May require an > IntrospectionUtils addition to the Beanutils package. > > > CONCEPTUAL API: > > public interface DynaBean { > > > // ---------------------------------------------------------------- > // Dynamic property configuration > // ---------------------------------------------------------------- > > void addDynamic(String name); // Unrestricted type > void addDynamic(String name, Class type); // Restricted type > void removeDyanamic(String name); // Remove property & value > void restrictDynamic(boolean restrict); // Are property names > // restricted to registered > // ones? (default=false) > // (can be changed) > > // ---------------------------------------------------------------- > // Property getters and setters. Behavior on previously > // unknown property names depends on the restrict setting > // ---------------------------------------------------------------- > > // Does this bean have a property of the specified name? > boolean contains(String name); > > // Getters return null on unknown property names > Object get(String name); // Simple > Object get(String name, int index); // Indexed > Object get(String name, String key); // Mapped > > // Setters are allowed to set null unless property is native. > // Optionally throw IllegalArgumentException if type is restricted > // and the value argument is not assignment-compatible > void set(String name, Object value); // Simple > void set(String name, int index, // Indexed > Object value); > void set(String name, String key, // Mapped > > } > > > Craig McClanahan > > > > > -- > To unsubscribe, e-mail: <mailto:commons-dev- > [EMAIL PROTECTED]> > For additional commands, e-mail: <mailto:commons-dev- > [EMAIL PROTECTED]> >
-- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
