java中一些常用的公共类

package common; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.Properties; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException; import javax.sql.DataSource; import org.apache.log4j.Logger; public class ConnUtil { private static String DRIVER; private static String URL; private static String USER; private static String PWD; private static boolean POOL; private static Logger log = Logger.getLogger(ConnUtil.class); static { Properties p = new Properties(); try { p.load(ConnUtil.class.getResourceAsStream("/db.properties")); DRIVER = p.getProperty("driver"); URL = p.getProperty("url"); USER = p.getProperty("user"); PWD = p.getProperty("pwd"); POOL = "true".equals(p.getProperty("pool")); log.info("成功加载连接配置文件！"); } catch (Exception e) { log.error("加载连接配置文件出错！原因：" + e); throw new DBAccessException("加载连接配置文件出错！原因：" + e.getMessage()); } } public static Connection getConn() { Connection conn = null; if (!POOL) {// 普通模式 try { Class.forName("com.mysql.jdbc.Driver"); conn = DriverManager.getConnection( "jdbc:mysql://localhost:3306/restrant", "root", "ok"); log.info("普通方式获得连接成功"); } catch (Exception e) { log.error("普通方式获得连接出错！"+e); throw new DBAccessException("普通方式获得连接出错！原因：" + e.getMessage()); } } else { try { Context ct = new InitialContext(); DataSource ds = (DataSource) ct.lookup("java:comp/env/jdbc/restrant"); conn = ds.getConnection(); log.info("连接池方式获得连接成功"); } catch (Exception e) { log.error("连接池方式获得连接出错！"+e); throw new DBAccessException("连接池方式获得连接出错！原因：" + e.getMessage()); } } return conn; } public static void close(Connection conn) { try { if (conn != null && !conn.isClosed()) { conn.close(); } } catch (Exception e) { log.error("关闭连接出错！"+e); throw new DBAccessException("关闭连接出错！原因：" + e.getMessage()); } } public static ResultSet executeQuery(Connection conn, String sql) { ResultSet res = null; try { PreparedStatement ps = conn.prepareStatement(sql); res = ps.executeQuery(); } catch (SQLException e) { log.error("执行查询出错！"+e); throw new DBAccessException("执行查询出错！！原因：" + e.getMessage()); } return res; } public static ResultSet executeQuery(Connection conn, String sql, Object[] params) { ResultSet res = null; try { PreparedStatement ps = conn.prepareStatement(sql); if (params != null && params.length > 0) { for (int i = 0; i < params.length; i++) { ps.setObject(i + 1, params[i]); } } res = ps.executeQuery(); } catch (Exception e) { log.error("执行查询出错！"+e); throw new DBAccessException("执行查询出错！！原因：" + e.getMessage()); } return res; } public static int executeUpdate(Connection conn, String sql, Object[] params) { int count = 0; try { PreparedStatement ps = conn.prepareStatement(sql); if (params != null && params.length > 0) { for (int i = 0; i < params.length; i++) { ps.setObject(i + 1, params[i]); } count = ps.executeUpdate(); } } catch (Exception e) { log.error("执行更新出错！"+e); throw new DBAccessException("执行更新出错！！原因：" + e.getMessage()); } return count; } }