estorebooks.java

数据库exercise4作业,JSP

package estore;
import java.sql.*;
import java.util.*;

/**
 * Class <b>EStoreBooks</b> stores
 * all of the books currently in the E-Store.
 *
 * @author A Jiayi
 * @version 1.0
 */
public class EStoreBooks {
	//Database connection parameter
	private final String driver = "org.postgresql.Driver";
	private final String url = "jdbc:postgresql:E-StoreDB";
	private final String user = "webuser";
	private final String passwd = "webuser";

	//Hashtable stores the title and isbn 
	//of all books in the E-Store.     
	private Hashtable tempBooks = new Hashtable(15, 8);

	/**
	* Constructor.Connect database and store
	* the title and isbn of all books into two arrays.
	*/
	public EStoreBooks() throws ClassNotFoundException, SQLException {
		Class.forName(driver);
		Connection conn = DriverManager.getConnection( url, user, passwd);
		Statement stmt = conn.createStatement();
		ResultSet rset = stmt.executeQuery("SELECT name, isbn FROM title5");
		while (rset.next()) {
			tempBooks.put(rset.getString("name"), rset.getString("isbn"));
		}
		rset.close();
		stmt.close();
		conn.close();
	}
	
	/**
	* Get the isbns of all books.
	* @param null
	* @return String[] isbns
	*/
	public String[] getIsbns() {
		int i = 0;
                String[] isbns = new String[tempBooks.size()];
                for (Enumeration isbnEnum = tempBooks.keys(); isbnEnum.hasMoreElements(); ) {
                        isbns[i++] = (String)isbnEnum.nextElement();
                }
                return isbns;
	}
	
	/**
	* Get the titles of all books.
	* @param  null
	* @return String[] titles
	*/
	public String[] getTitles() {
	        int i = 0;
                String[] titles = new String[tempBooks.size()];
                for (Enumeration isbnEnum = tempBooks.keys(); isbnEnum.hasMoreElements(); ) {
                        titles[i++] = (String)tempBooks.get(isbnEnum.nextElement());
                }
                return titles;
	}

	/**
	* Get the title of a book gived isbn.
	* @param String isbn
	* @return String title
	*/
	public String getTitle(String isbn) {
		return (String)tempBooks.get(isbn);
	}
}