These two approaches
- The contract-first approach, where you define the contract first with XSD and WSDL and the generate the Java classes from the contract.
- The contract-last approach where you define the Java classes first and then generate the contract, which is the WSDL file from the Java classes.
Note: The WSDL describes all operations that the service provides, locations of the endpoints (i.e.e where the services can be invoked), and simple and complex elements that can be passed in requests and responses.