Often you might like to get access to information about a DynamicBean that has not yet been instantiated. For instance, imagine that you have a DynamicBean based on JDBC ResultSets. You might like to know what properties a ResultSet for some query would have if the query took place. Using the above techniques, there’s no way to do this; where would the DynamicBeanInfo come from?
Imagine that you have a Query class or interface, which describes a query that generates a ResultSet when executed. It would be nice to have a way to get a DynamicBeanInfo from the Query without executing it. We’d like to use the Query (apart from its other functions) as a “dynamic type”: it can provide information about the dynamic beans that it is capable of generating.
Dynamic Beans provides an interface called DynamicBeanTyper. It contains a single method:
public DynamicBeanInfo getBeanInfoFromType(Object pDescription)
throws IntrospectionException;
The purpose of this method is to return a DynamicBeanInfo from an object (such as our imagined Query) that plays the role of a dynamic type. You register a DynamicBeanTyper by calling DynamicBeans.registerBeanTyper(Class, DynamicBeanTyper). The class parameter is the class of a dynamic type, not the class of a DynamicBean. In this example, it would be Query.class.
Once our example DynamicBeanTyper is registered, the static method DynamicBeans.getBeanInfoFromType(Object) can be used to obtain a DynamicBeanInfo for any Query.
One final, useful twist: instances of java.lang.Class (i.e. static types) act as dynamic types. In other words, there is a DynamicBeanTyper registered for Class.class. Its function is to return a DynamicBeanInfo that describes an instance of the given class, as analyzed by JavaBeans introspection. You could, for instance, call DynamicBeans.getBeanInfoFromType(Date.class), and the result would be a DynamicBeanInfo describing an instance of Date. This is exactly the same result you would get by calling DynamicBeans.getBeanInfo() on an instance of Date.
