Distributed Web Software  Presentation-based, e.g., dynamic web pages  Service-based – Web Services

Without Web Service Layer: Content and Presentation mixed Database ADatabase BDatabase CDatabase D Servlet html

Web Services: Aggregators Database A Database BDatabase C Database D Service B Service A Service C Service D Aggregator Servlet html

View How You Want Database Service

View How You Want, Examples  Show Google Scholar as a graph  Various Bookstores using Amazon

Importance of Web Services  Larry Page, on why Google introduced its search API: “Within a few years, there will be more programs (agents) accessing Google than people accessing Google.”

Sample Web Service: The Google API   Your Java/.Net program can call Google functions.  SOAP underneath the hood  Let’s try it…

Google API Tutorial  Download at  Extract files from zip into directory “Google”  Register to get a key (same page).  Open the readme file that was downloaded.  Run the demo program from “Google” dir: java -cp googleapi.jar com.google.soap.search.GoogleAPIDem o search Foo Where is your registration key and Foo is the item you wish to search for.

Google API Tutorial  Check out the Google API Go to javadoc directory and click on index.html API Reference page is “APIs_Reference.html”  Check out demo program GoogleAPIDemo.java in main dir. Run it.

Google API Assignment  Write a class USFInward with a main program that lists the URLs (only) of five web pages that point to  Instead of beginning from scratch, modify GoogleAPIDemo.java.

Google Assignment Solution  SaveAs GoogleAPIDemo.java to USFInward.java.  Rename class in source file.  Replace the package statement at top with: import com.google.soap.search.*;  Modify code to perform requested actions.  javac -classpath googleapi.jar USFInward.java  Add “.” to classpath in execution line: java -cp.;googleapi.jar USFInward.java

Google Solution Issues  Define a private static final int MAX=5  Search string should be “linkto:  Use GoogleSearchResult.getResults() to get array, then loop on each GoogleSearchResultElement calling getURL()

Google Web Service: Under the Hood Google DB SOAP API Java APIC# API Java ClientC# ClientOther Client Google Crawler

Amazon Web Service  /panama/associates/ntg/browse/- / /

UDDI Registries

Writing Web Service Clients in Java WSDL – Web Service Description Language UDDI- Registry of Web Services WSDL wscompile Java stubs 1.Fine Web Service WSDL document in UDDI. 2.Generate Java stubs to access service: 3. Write Java client that accesses service through stubs.

Creating a Web Service  Similar to RMI, define a “Remote” interface public interface MathService extends Remote { int add(int x, int y) throws RemoteException; //… }  Implement the interface public class MathServiceImpl implements MathService { public int add( int x, int y) throws RemoteException; { return x+y; }

Creating a Web Service (cont.)  Use wsdeploy to create “ties” and WSDL file: wsdeploy WSDL Java ties MathService.java MathServiceImpl.java Package and Deploy– Build Web App Resource (WAR) file web.xml descriptor file