bmp5.html

jdbc书

and
<A HREF="./Code/auction/AuctionItemBean.java">AuctionItemBean</A> 
to retrieve each Bean in turn by calling
<CODE>findByPrimaryKey</CODE> on each primary
key in the list. This is a container-managed 
search based on the <CODE>finder</CODE> mechanism described in Chapter 2. 

</FONT>

<PRE>
//Iterate through search results
while ((enum != null) &amp;&amp; 
    enum.hasMoreElements())) {
 while(enum.hasMoreElements(in)) {

//Locate auction items
 AuctionItem ai=ahome.findByPrimaryKey((
    AuctionItemPK)enum.nextElement());
 displayLineItem(ai, out);
 }
}
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<A NAME="bean"></A>
<H3>SearchBean</H3>

The <A HREF="./Code/search/SearchBean.java">SearchBean.java</A>
class defines a Bean-managed search for the primary keys
of auction items with <CODE>summary</CODE> fields that
contain characters matching the search string. This Bean  
establishes a database connection, and 
provides the <CODE>getMatchingItemsList</CODE> and 
<CODE>EJBCreate</CODE> methods. 

<H4>Database Connection</H4>

Because this Bean manages its own database access and search, it
has to establish its own database connection. It cannot rely on the
container to do this.

<P>
The database connection is established by instantiating a static
<CODE>Driver</CODE> class and providing the 
<CODE>getConnection</CODE> method.
The <CODE>getConnection</CODE> method queries the static
<CODE>DriverManager</CODE> class for a registered database driver
that matches the Uniform Resource Locator (URL) . In this case, the URL is
<CODE>weblogic.jdbc.jts.Driver</CODE>.

</FONT>

<PRE>
//Establish database connection
  static {
    new weblogic.jdbc.jts.Driver();
  }

  public Connection getConnection()
        throws SQLException {
    return DriverManager.getConnection(
        "jdbc:weblogic:jts:ejbPool");
  }
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<H4>Get Matching Items List</H4>

The <CODE>getMatchingItemsList</CODE> method
looks up <CODE>AuctionItemsBean</CODE>
and creates a <CODE>PreparedStatement</CODE> object for querying
the database for <CODE>summary</CODE> fields that contain 
the search string. Data is read from the database into a
<CODE>ResultSet</CODE>, stored in a <CODE>Vector</CODE>, and
returned to <CODE>AuctionServlet</CODE>.

</FONT>

<PRE>
  public Enumeration getMatchingItemsList(
	String searchString) 
	throws RemoteException {

    ResultSet rs = null;
    PreparedStatement ps = null;
    Vector v = new Vector();
    Connection con = null;

    try{
//Get database connection
      con=getConnection();
//Create a prepared statement for database query
      ps=con.prepareStatement("select id from 
	auctionitems where summary like ?");
      ps.setString(1, "%"+searchString+"%");
//Execute database query
      ps.executeQuery();
//Get results set
      rs = ps.getResultSet();
//Get information from results set
      AuctionItemPK pk;
      while (rs.next()) {
        pk = new AuctionItemPK();
        pk.id = (int)rs.getInt(1);
//Store retrieved data in vector
	v.addElement(pk);
      }
      rs.close();
      return v.elements();

    }catch (Exception e) {
	System.out.println("getMatchingItemsList: 
			    "+e);
	return null;
    }finally {
      try {
	 if(rs != null) {
           rs.close();
         }
	 if(ps != null) {
           ps.close();
         }
	 if(con != null) {
           con.close();
         }
      } catch (Exception ignore) {}
    }
  }
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<H4>Create Method</H4>

The <CODE>ejbCreate</CODE> method creates an
<CODE>javax.naming.InitialContext</CODE> object. This is a
Java<FONT SIZE="-2"><SUP>TM</SUP></FONT> Naming and Directory (JNDI) class that lets
<CODE>SearchBean</CODE> access the database without
relying on the container.

</FONT>

<PRE>
  public void ejbCreate() throws CreateException, 
    RemoteException {
    Properties p = new Properties();
    p.put(Context.INITIAL_CONTEXT_FACTORY, 
	"weblogic.jndi.TengahInitialContextFactory");
    try{
	ctx = new InitialContext(p);
    }catch(Exception e) {
	System.out.println("create exception: "+e);
    }
  }
</PRE>
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