SQLHelper、DBUtil终极封装

DBUtil.java

 package org.guangsoft.util;

 import java.io.InputStream;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.ResultSetMetaData;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Properties;

 import org.apache.commons.beanutils.BeanUtils;

 /**
  *
  * @author guanghe
  */
 public class DBUtil
 {
     //定义连接资源
     private static Connection ct = null;
     private static PreparedStatement ps = null;
     private static ResultSet rs = null;

     //定义配置参数
     private static String driver = null;
     private static String url = null;
     private static String username = null;
     private static String password = null;

     //定义配置文件引入
     private static Properties pp = null;
     private static InputStream is = null;

     //读取配置参数，加载驱动
     static
     {
         try
         {
             pp = new Properties();
             is = DBUtil.class.getClassLoader().getResourceAsStream("org/guangsoft/util/db.properties");
             pp.load(is);
             driver = pp.getProperty("driver");
             url = pp.getProperty("url");
             username = pp.getProperty("username");
             password = pp.getProperty("password");
             Class.forName(driver);
         }
         catch (Exception e)
         {
             e.printStackTrace();
             System.exit(0);
         }
         finally
         {
             try
             {
                 is.close();
             }
             catch (Exception e)
             {
                 e.printStackTrace();
             }
             is = null;
         }
     }

     //获取连接
     public static Connection getConnection()
     {
         try
         {
             ct = DriverManager.getConnection(url, username, password);
         }
         catch (Exception e)
         {
             e.printStackTrace();
         }
         return ct;
     }

     //执行DQL查询
     public static<T> List<T> executeQuery(String sql, Object[] parameters,Class<T> clazz)
     {
         List<T> list = new ArrayList<T>();
         try
         {
             //得到数据结果集
             ct = getConnection();
             ps = ct.prepareStatement(sql);
             if (parameters != null)
             {
                 for (int i = 0; i < parameters.length; i++)
                 {
                     ps.setObject(i + 1, parameters[i]);
                 }
             }
             rs = ps.executeQuery();

             //封装数据
             ResultSetMetaData metaData = rs.getMetaData();
             int columnCount = metaData.getColumnCount();
             while(rs.next())
             {
                 T t = clazz.newInstance();
                 for(int i = 0; i < columnCount; i++)
                 {
                     String columnName = metaData.getColumnName(i+1);
                     Object value = rs.getObject(columnName);
                     BeanUtils.copyProperty(t, columnName, value);
                 }
                 list.add(t);
             }
         }
         catch(Exception e)
         {
             e.printStackTrace();
         }
         finally
         {
             close();
         }
         return list;
     }

     //执行DML更新
     public static int executeUpdate(String sql, Object[] parameters)
     {
         try
         {
             ct = getConnection();
             ps = ct.prepareStatement(sql);
             if (parameters != null)
             {
                 for (int i = 0; i < parameters.length; i++)
                 {
                     ps.setObject(i + 1, parameters[i]);
                 }
             }
             return ps.executeUpdate();
         }
         catch (Exception e)
         {
             e.printStackTrace();
         }
         finally
         {
             close();
         }
         return 0;
     }

     //关闭所有资源连接
     public static void close()
     {
         if (rs != null)
         {
             try
             {
                 rs.close();
             }
             catch (Exception e)
             {
                 e.printStackTrace();
             }
             rs = null;
         }
         if (ps != null)
         {
             try
             {
                 ps.close();
             }
             catch (Exception e)
             {
                 e.printStackTrace();
             }
             ps = null;
         }
         if (null != ct)
         {
             try
             {
                 ct.close();
             }
             catch (Exception e)
             {
                 e.printStackTrace();
             }
             ct = null;
         }
     }

 }

db.properties

 driver = com.mysql.jdbc.Driver
 url = jdbc:mysql://localhost:3306/test
 username = root
 password =root