For this purpose, the data handler class needs to implement icc.net.DataHandling by containing the methods public void process (Package pkg) and public void handleException (Exception e). For example:
public void process(Package pkg) {
IDCard source = pkg.from();
Object content = pkg.content;
System.out.println("Received package from " +
source.name() + " with content of class " +
pkg.content.getClass().getName());
}
public void handleException(Exception e) {
System.out.println("Caught "+ e);
}
The data handler class can register itself to the speaker as follows:
speaker.setDataHandler(this);
2. Creating requests
All service methods for creating data requests are listed with specification of the icc.db class files they can be found in:
Document requests: File, WorkFile
Partner requests: Partner, Team
Project requests: Project, Access, Cube, Phase
Document search requests: Folder, Select, Cube
Mediator service requests: icc.net.DataRequest
Attention: Requests cannot be modified after creation. Read access to requests is limited as well. See below for more information on how to deal with these restrictions.
3. Altering the arguments of a requests
Once created, requests cannot be modified. However, sometimes it may be necessary to alter the arguments of a request after creation, e.g., when created in a different process. One of the following two methods can be used to achieve this.
a. Delaying the creation
If the request can be created from an object (non-static service method), this object (or objects) can be passed on by the first process, in order to create the request just before sending it off.
b. Providing separate access to the arguments
Otherwise, the arguments can additionally be provided as separate objects to the request, though within a single package when passed on over the network. When the argument objects are manipulated, so are the arguments in the request.
4. Sending requests
a. Chaining requests
Multiple requests can be sent as one, by attaching them to one another:
request1.attach(request2);
attaches request2 to request1, or at the end of the chain of requests represented by request1.
b. Packaging a request (chain)
In order to be serviced, a request must be sent to IDCard.SERVICE. The result will be returned to the sender, unless otherwise specified in the package.
new Package(IDCard.SERVICE, request)
prepares a request to be sent off.
5. Processing the results
It is assumed that the result arrives as a package pkg to the process method and that the content of this package is an instance of the DataRequest class:
DataRequest request = (DataRequest) pkg.content;
a. Was the request successful?
if (!request.successful())
System.out.println("unsuccessful " + request.toString());
A request is unsuccessful if the service threw an exception when processing the request, or if the service in question was not available, resulting in a nonServicedRequest exception.
In both cases, the thrown Exception object is provided as the result of the request:
Exception result = (Exception) request.result();
b. Interpreting the result
To aid in the processing, the following information can be extracted from the result:
The name of the service
String name = request.service();
The resulting object
Object result = request.result();
The number of arguments to the request
int number = request.arguments();
Each argument to the request
Object arg1 = request.argument(0);
c. Chained results
If multiple requests were attached into a chain, their results may arrive attached as well (though they don't need to).
if ((request = request.detach()) != null)
retrieves the next attached result, and checks if it is non-null.
6. Handling respective results
Examples are provided on how to deal with the results from each type of data requests:
Document results
Partner results
Project results
Document search results
Mediator service results
Putting it all together: Processing the results
This java source file shows a data handler class handling the results from data requests, as compiled from the information provided higher.
 Last updated: 12 June 1999
Please send suggestions, comments and bug reports to tuncer@arch.ethz.ch
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