A Java Object Data Source is useful when your data cannot be accessed via common standards JDBC, SOAP, XML or if you have a pre-existing JAVA API to which you wish to connect.
Creating a Java Object Data Source requires, at minimum, the creation of a Data Loader class. A data loader class can be based on the ‘inetsoft.uql. object.DataLoader’ interface, the ‘inetsoft.uql.object.DataLoader2’ interface or ‘Introspection’ based (by complying to the Java Bean conventions). In some cases an additional ‘Data Helper’ class is also needed to describe the structure of the data being returned.
If your data has a ‘flat’ tabular structure, the Data Loader should be based on the ‘DataLoader2’ interface. It is the simplest and most convenient option; only deals with primitive data types and does not need any Data Helper class.
For data which has a hierarchy (especially a recursive one) the data loader should be based on the ‘DataLoader’ interface or Introspection. e.g. 1 forest had N Trees; 1 tree has N leaves. OR An ‘Employee’ has a ‘Manager’ who is also an ‘Employee’ etc.
Data Loader based on Introspection
A data loader that does not implement the DataLoader interface is completely based on introspection and must satisfy the following requirements:
• the class must have a default constructor that requires no arguments and
• the class must have methods that return a collection of objects. The collection may be an object of the subclass of either:
When a data source is defined based on the data loader, the query engine uses introspection to discover all public methods that return one of the collection types. Each method is then added to the data source as a request.
If a request is created from a method that requires parameters, the parameter values can be specified as part of the data source or they can be declared as variables, which become the data source parameters.
For each request, the user needs to specify the object type (class) returned by the request. This class will be probed by the query engine to find all of the public getter methods and treat them as the fields in the record. During probing, the query engine follows the object references, thus, the meta data may be a hierarchical structure.
Data Loader based on DataLoader Interface
While the default introspection based data loader works well with the classes that match the defined convention, the DataLoader interface provides a more flexible way to define the procedure to load objects. The design and runtime of the data source works in the same way as an introspection based data loader, except that the DataLoader interface is used for meta-data discovering and runtime execution without relying on introspection.
The DataLoader interface defines the following four methods:
InetSoft Technology Corp.
InetSoft Technology Corp.