8.3 Javaクラスの作成
データベース表を作成した後は、発注書システムに必要な操作を考慮して、適切なJavaメソッドを作成します。前述の例で定義した表に基づいた簡単なシステムでは、顧客の登録、部品の保管、発注の入力などのメソッドが必要です。これらのメソッドは、JavaクラスPOManager
で次のように実装できます。
import java.sql.*; import java.io.*; import oracle.jdbc.*; public class POManager { public static void addCustomer (int custNo, String custName, String street, String city, String state, String zipCode, String phoneNo) throws SQLException { String sql = "INSERT INTO Customers VALUES (?,?,?,?,?,?,?)"; try { Connection conn = DriverManager.getConnection("jdbc:default:connection:"); PreparedStatement pstmt = conn.prepareStatement(sql); pstmt.setInt(1, custNo); pstmt.setString(2, custName); pstmt.setString(3, street); pstmt.setString(4, city); pstmt.setString(5, state); pstmt.setString(6, zipCode); pstmt.setString(7, phoneNo); pstmt.executeUpdate(); pstmt.close(); } catch (SQLException e) { System.err.println(e.getMessage()); } } public static void addStockItem (int stockNo, String description, float price) throws SQLException { String sql = "INSERT INTO StockItems VALUES (?,?,?)"; try { Connection conn = DriverManager.getConnection("jdbc:default:connection:"); PreparedStatement pstmt = conn.prepareStatement(sql); pstmt.setInt(1, stockNo); pstmt.setString(2, description); pstmt.setFloat(3, price); pstmt.executeUpdate(); pstmt.close(); } catch (SQLException e) { System.err.println(e.getMessage()); } } public static void enterOrder (int orderNo, int custNo, String orderDate, String shipDate, String toStreet, String toCity, String toState, String toZipCode) throws SQLException { String sql = "INSERT INTO Orders VALUES (?,?,?,?,?,?,?,?)"; try { Connection conn = DriverManager.getConnection("jdbc:default:connection:"); PreparedStatement pstmt = conn.prepareStatement(sql); pstmt.setInt(1, orderNo); pstmt.setInt(2, custNo); pstmt.setString(3, orderDate); pstmt.setString(4, shipDate); pstmt.setString(5, toStreet); pstmt.setString(6, toCity); pstmt.setString(7, toState); pstmt.setString(8, toZipCode); pstmt.executeUpdate(); pstmt.close(); } catch (SQLException e) { System.err.println(e.getMessage()); } } public static void addLineItem (int lineNo, int orderNo, int stockNo, int quantity, float discount) throws SQLException { String sql = "INSERT INTO LineItems VALUES (?,?,?,?,?)"; try { Connection conn = DriverManager.getConnection("jdbc:default:connection:"); PreparedStatement pstmt = conn.prepareStatement(sql); pstmt.setInt(1, lineNo); pstmt.setInt(2, orderNo); pstmt.setInt(3, stockNo); pstmt.setInt(4, quantity); pstmt.setFloat(5, discount); pstmt.executeUpdate(); pstmt.close(); } catch (SQLException e) { System.err.println(e.getMessage()); } } public static void totalOrders () throws SQLException { String sql = "SELECT O.PONo, ROUND(SUM(S.Price * L.Quantity)) AS TOTAL " + "FROM Orders O, LineItems L, StockItems S " + "WHERE O.PONo = L.PONo AND L.StockNo = S.StockNo " + "GROUP BY O.PONo"; try { Connection conn = DriverManager.getConnection("jdbc:default:connection:"); PreparedStatement pstmt = conn.prepareStatement(sql); ResultSet rset = pstmt.executeQuery(); printResults(rset); rset.close(); pstmt.close(); } catch (SQLException e) { System.err.println(e.getMessage()); } } static void printResults (ResultSet rset) throws SQLException { String buffer = ""; try { ResultSetMetaData meta = rset.getMetaData(); int cols = meta.getColumnCount(), rows = 0; for (int i = 1; i <= cols; i++) { int size = meta.getPrecision(i); String label = meta.getColumnLabel(i); if (label.length() > size) size = label.length(); while (label.length() < size) label += " "; buffer = buffer + label + " "; } buffer = buffer + "\n"; while (rset.next()) { rows++; for (int i = 1; i <= cols; i++) { int size = meta.getPrecision(i); String label = meta.getColumnLabel(i); String value = rset.getString(i); if (label.length() > size) size = label.length(); while (value.length() < size) value += " "; buffer = buffer + value + " "; } buffer = buffer + "\n"; } if (rows == 0) buffer = "No data found!\n"; System.out.println(buffer); } catch (SQLException e) { System.err.println(e.getMessage()); } } public static void checkStockItem (int stockNo) throws SQLException { String sql = "SELECT O.PONo, O.CustNo, L.StockNo, " + "L.LineNo, L.Quantity, L.Discount " + "FROM Orders O, LineItems L " + "WHERE O.PONo = L.PONo AND L.StockNo = ?"; try { Connection conn = DriverManager.getConnection("jdbc:default:connection:"); PreparedStatement pstmt = conn.prepareStatement(sql); pstmt.setInt(1, stockNo); ResultSet rset = pstmt.executeQuery(); printResults(rset); rset.close(); pstmt.close(); } catch (SQLException e) { System.err.println(e.getMessage()); } } public static void changeQuantity (int newQty, int orderNo, int stockNo) throws SQLException { String sql = "UPDATE LineItems SET Quantity = ? " + "WHERE PONo = ? AND StockNo = ?"; try { Connection conn = DriverManager.getConnection("jdbc:default:connection:"); PreparedStatement pstmt = conn.prepareStatement(sql); pstmt.setInt(1, newQty); pstmt.setInt(2, orderNo); pstmt.setInt(3, stockNo); pstmt.executeUpdate(); pstmt.close(); } catch (SQLException e) { System.err.println(e.getMessage()); } } public static void deleteOrder (int orderNo) throws SQLException { String sql = "DELETE FROM LineItems WHERE PONo = ?"; try { Connection conn = DriverManager.getConnection("jdbc:default:connection:"); PreparedStatement pstmt = conn.prepareStatement(sql); pstmt.setInt(1, orderNo); pstmt.executeUpdate(); sql = "DELETE FROM Orders WHERE PONo = ?"; pstmt = conn.prepareStatement(sql); pstmt.setInt(1, orderNo); pstmt.executeUpdate(); pstmt.close(); } catch (SQLException e) { System.err.println(e.getMessage()); } } }