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Chapter 2 Continued: Container-Managed finder Methods

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The auction house search facility is implemented as a container-managed finder. method. It starts when the end user types in a search string and clicks the Submit button on the home page to locate an auction item. As shown in the diagram, the browser passes the search string to the AuctionServlet.searchItem method, which then passes it to the BidderBean.getMatchingItemsList method.

At this point, BidderBean.getMatchingItemsList passes the search string to the findAllMatchingItems method declared in the AuctionItemHome interface. This method is a finder method, and container implementations vary in how they handle calls to finder methods. BEA Weblogic containers look in the Bean's deployment descriptor for information on a Bean's finder methods.

In the case of the search, the deployment descriptor maps the search string passed to AuctionItemHome.findAllMatchingItems to the summary field in the underlying AuctionItems database table. This tells the Enterprise JavaBeans^TM server to retrieve data for all auction items with a summary field that contains text that matches the search string.

This section walks through the different parts of the finder-based search code. Chapter 3 describes how to create a Bean-managed search to handle complex queries and searches that span more than one Bean type (entity and session Beans) or database tables.

• AuctionServlet.searchItems
• BidderBean.getMatchingItemsList
• AuctionItemHome.findAllMatchingItems
• AuctionItemBean Deployment Descriptor

---

AuctionServlet.searchItems

The searchItems method retrieves the text string from the browser, creates an HTML page to display the search results, and passes the search string to the BidderBean.getMatchingItemsList method. BidderBean is a session Bean that retrieves lists of auction items and checks the user ID and password for end users seeking to bid on auction items.

The search results are returned to this method in an Enumeration variable.

private void searchItems(ServletOutputStream out,
	HttpServletRequest request) 
	throws IOException {

//Retrieve search string
  String searchString=request.getParameter(
	"searchString");

//Create HTML page
  String text = "Click Item number for description 
	and to place bid.";
  setTitle(out, "Search Results");
  try {
        addLine("<BR>"+text, out);

//Look up home interface for BidderBean
        BidderHome bhome=(BidderHome) ctx.lookup(
		"bidder");

//Create remote interface for BidderBean
        Bidder bid=bhome.create();

//Pass search string to BidderBean method
        Enumeration enum=(Enumeration)
          bid.getMatchingItemsList(searchString);

        if(enum != null) {
          displayitems(enum, out);
          addLine("", out);
        }
  } catch (Exception e) {
    addLine("AuctionServlet Search Items error", 
	out);
    System.out.println("AuctionServlet <newlist>:
	"+e);
  }
    out.flush();
}

The search results are returned to this method in an Enumeration variable.

public Enumeration getMatchingItemsList(
		String searchString) 
	throws RemoteException {

  Enumeration enum=null;
  try{
//Create Home interface for AuctionItemBean
    AuctionItemHome home = (AuctionItemHome) 
	ctx.lookup("auctionitems");

//Pass search string to Home interface method
    enum=(Enumeration)home.findAllMatchingItems(
	searchString);
  }catch (Exception e) {
    System.out.println("getMatchingItemList: "+e);
    return null;
  }
  return enum;
}

When using these containers, even if the Bean has finder method implementations, they are ignored and the deployment descriptor settings are consulted instead.

//Declare method in Home interface
  public Enumeration findAllMatchingItems(
		String searchString) 
	throws FinderException, RemoteException;

The deployment descriptor for AuctionItemBean provides finderDescriptors for all finder methods declared in the AuctionItemHome interface. The finderDescriptor for the findAllMatchingItems method maps the search string to the summary field in the underlying AuctionItems database table. This tells the Enterprise JavaBeans server to retrieve the data for all table rows with a summary field that matches the text in the search string.

(finderDescriptors
 "findAllItems()"         "(= 1 1)"
 "findAllNewItems(java.sql.Date newtoday)" 
	"(= startdate $newtoday)"
 "findAllClosedItems(java.sql.Date closedtoday)" 
	"(= enddate $closedtoday)"
 "findAllMatchingItems(String searchString)" 
	"(like summary $searchString)"
); end finderDescriptors

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