财务软件系统（第一版）

				package caiwu;
				
				import java.sql.*;
				
				public class DBConnect {
					private Connection conn = null;
					private Statement stmt = null;
					private PreparedStatement prepstmt = null;
					private DBConnectionManager dcm=null;
				
				    void init() {
				        dcm = DBConnectionManager.getInstance();
						conn = dcm.getConnection("mysql");
				    }
				
					/**
					 * 构造数据库的连接和访问类
					 */
					public DBConnect() throws Exception {
				        init();
						stmt = conn.createStatement();
					}
				
				    public DBConnect(int resultSetType, int resultSetConcurrency)
				            throws Exception {
				        init();
				        stmt = conn.createStatement(resultSetType, resultSetConcurrency);
				    }
				
				    /**
				     * 构造数据库的连接和访问类
				     * 预编译SQL语句
				     * @param sql SQL语句
				     */
					public DBConnect(String sql) throws Exception {
				        init();
						this.prepareStatement(sql);
					}
				
					public DBConnect(String sql, int resultSetType, int resultSetConcurrency)
				            throws Exception {
				        init();
						this.prepareStatement(sql, resultSetType, resultSetConcurrency);
					}
				
					/**
					 * 返回连接
					 * @return Connection 连接
					 */
					public Connection getConnection() {
						return conn;
					}
				
					/**
					 * PreparedStatement
					 * @return sql 预设SQL语句
					 */
					public void prepareStatement(String sql) throws SQLException {
						prepstmt = conn.prepareStatement(sql);
					}
				
					public void prepareStatement(String sql, int resultSetType, int resultSetConcurrency)
				            throws SQLException {
						prepstmt = conn.prepareStatement(sql, resultSetType, resultSetConcurrency);
					}
				
					/**
					 * 设置对应值
				     *
					 * @param index 参数索引
					 * @param value 对应值
					 */
					public void setString(int index,String value) throws SQLException {
						prepstmt.setString(index, value);
					}
					public void setInt(int index,int value) throws SQLException {
						prepstmt.setInt(index,value);
					}
					public void setBoolean(int index,boolean value) throws SQLException {
						prepstmt.setBoolean(index,value);
					}
					public void setDate(int index,Date value) throws SQLException {
						prepstmt.setDate(index,value);
					}
					public void setLong(int index,long value) throws SQLException {
						prepstmt.setLong(index,value);
					}
					public void setFloat(int index,float value) throws SQLException {
						prepstmt.setFloat(index,value);
					}
					public void setBytes(int index,byte[] value) throws SQLException{
						prepstmt.setBytes(index,value);
					}
				
				
				
				    public void clearParameters()
				        throws SQLException
				    {
				        prepstmt.clearParameters();
					prepstmt=null;
				    }
					/**
					 * 返回预设状态
					 */
					public PreparedStatement getPreparedStatement() {
						return prepstmt;
					}
					/**
					 * 返回状态
					 * @return Statement 状态
					 */
					public Statement getStatement() {
						return stmt;
					}
					/**
					 * 执行SQL语句返回字段集
					 * @param sql SQL语句
					 * @return ResultSet 字段集
					 */
					public ResultSet executeQuery(String sql) throws SQLException {
						if (stmt != null) {
							return stmt.executeQuery(sql);
						}
						else return null;
					}
				
					public ResultSet executeQuery() throws SQLException {
						if (prepstmt != null) {
							return prepstmt.executeQuery();
						}
						else return null;
					}
				
					/**
					 * 执行SQL语句
					 * @param sql SQL语句
					 */
					public void executeUpdate(String sql) throws SQLException {
						if (stmt != null)
							stmt.executeUpdate(sql);
					}
					public void executeUpdate() throws SQLException {
						if (prepstmt != null)
							prepstmt.executeUpdate();
					}
					/**
					 * 关闭连接
					 */
					public void close() throws Exception {
						if (stmt != null)  {
							stmt.close();
							stmt = null;
						}
						if (prepstmt != null) {
							prepstmt.close();
							prepstmt = null;
						}
						if (conn!=null)
						{
				
							dcm.freeConnection("mysql",conn);
				
						}
				
					}
				}