JSP Servlet JavaBean的网上交易系统理论课贯穿案例

package y2javaee.sg.util; import java.util.*; import java.sql.*; import javax.servlet.jsp.jstl.sql.*; /* * 通用的JDBC数据库访问类 * Y2JavaEE的ch06的工具类 */ public class SQLCommandBean { private Connection conn; private String sqlValue; private List values; /** * 设定连接类 */ public void setConnection(Connection conn) { this.conn = conn; } /** * 设定SQL语句. */ public void setSqlValue(String sqlValue) { this.sqlValue = sqlValue; } /** * 设定SQL语句的参数 */ public void setValues(List values) { this.values = values; } /** * 执行查询 * * @return a javax.servlet.jsp.jstl.sql.Result object * @exception SQLException */ public Result executeQuery() throws SQLException { Result result = null; ResultSet rs = null; PreparedStatement pstmt = null; Statement stmt = null; try { if (values != null && values.size() > 0) { // Use a PreparedStatement and set all values pstmt = conn.prepareStatement(sqlValue); setValues(pstmt, values); rs = pstmt.executeQuery(); } else { // Use a regular Statement stmt = conn.createStatement(); rs = stmt.executeQuery(sqlValue); } result = ResultSupport.toResult(rs); }finally { if (rs != null) { try {rs.close();} catch (SQLException e) {} } if (stmt != null) { try {stmt.close();} catch (SQLException e) {} } if (pstmt != null) { try {pstmt.close();} catch (SQLException e) {} } } return result; } /** * 执行Update语句 * * @return the number of rows affected * @exception SQLException */ public int executeUpdate() throws SQLException { int noOfRows = 0; ResultSet rs = null; PreparedStatement pstmt = null; Statement stmt = null; try { if (values != null && values.size() > 0) { // Use a PreparedStatement and set all values pstmt = conn.prepareStatement(sqlValue); setValues(pstmt, values); noOfRows = pstmt.executeUpdate(); } else { // Use a regular Statement stmt = conn.createStatement(); noOfRows = stmt.executeUpdate(sqlValue); } } finally { if (rs != null) { try {rs.close();} catch (SQLException e) {} } if (stmt != null) { try {stmt.close();} catch (SQLException e) {} } if (pstmt != null) { try {pstmt.close();} catch (SQLException e) {} } } return noOfRows; } /** * 设定语句的参数. * * @param pstmt the PreparedStatement * @param values a List with objects * @exception SQLException */ private void setValues(PreparedStatement pstmt, List values) throws SQLException { for (int i = 0; i < values.size(); i++) { Object v = values.get(i); // Set the value using the method corresponding to the type. // Note! Set methods are indexed from 1, so we add 1 to i pstmt.setObject(i + 1, v); } } }