Servlet API  for RAP version 1.2.1

Last Updated - 04/06/00 NRD

package ServletAPI   

• new package name:  was Servlet.Interface

All RAP Servlets should implement this interfaces:

• Servlet.java

  changes from RAP 1.1

  • was ServletInterface.java
  • no longer inherits from SignatureGenerator interface
  • added GetTypeSignatureID() method
  • GetServletDescriptor() instead of GetServletDescription() to match new IDL
  • SetDataStream() returns void instead of boolean
  • added throws clauses to method declarations
  • addition of GetValidResultType() method

All RAP SignatureGenerators should implement this interfaces:

• SignatureGenerator.java

  changes from RAP 1.1

  • was SignatureInterface.java
  • method names changed to match new IDL
  • added throws clauses to method declarations

These are the supporting classes for the RAP Servlet API:

• AttachmentDef.java
  • was Definition.java
• AttachmentException.java
• AttachmentRoleSpec.java
  • was AttachmentRoleSpecification.java
  • now "requiredIndicator" variable  (was "optionalIndicator")
• Domain.java
  • new, used in ParameterDescription
• MethodSignature.java
  • was MethodDescription.java
  • instance variables start with lowercase letter to match IDL
  • no more ReturnMIMEType
  • addition of returnType
• MIMETypedStream.java
  • was MethodReturn.java
  • "data" instance variable was "buffer"
  • removal of constructor with no arguments (functionality supplied by java, no need to state it)
• Ordinality.java
  • instance variables match IDL
• ParameterDescription.java
  • instance variables start with lowercase letter to match IDL
• ServletAPIException.java
  • was SystemException.java

Additional Info on some changes:

1. AttachmentRoleSpec: "requiredIndicator" instead of "optionalIndicator". We feel the intuitive question is "is it required?" not "is it optional?". The latter means you have to reason through a double negative to determine whether or not you must attach a DataStream.
2. we moved the list of returnMIMEtypes from the MethodSignature to a method in the Servlet interface (with a MethodSignature as a parameter so you get this info per implemented method). We can see that a client or user might want to know whether a RAP Dissemination will/can produce results of a particular MIME type, without actually performing the Dissemination. However, it seems wrong to have each MethodSignature indicate the possible MIME types that would be returned, as this could a) cause a proliferation of TypeSignatures that are the same except for return types and b) cause quicker obsolescence of TypeSignatures due to obsolescence of MIME types. It also seems wrong for the SignatureGenerator to indicate possible return types per method for the same reasons: this would still associate the return types for each method with the TypeSignature. Since a Servlet is an implementation of a TypeSignature, it seems more sensible to try to specify this information in the Servlet: the potential return types pertain to the implementation of each MethodSignature. This further makes sense as return types may be dependent on the MIME of the Attached DataStreams, and that is specified in the Servlet attachment specification. Have we overlooked something?