Java基础~JDBC连接数据库

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import org.apache.commons.beanutils.BeanUtils;
public class JdbcUtils {  
  private static String Driver="";  
  private static String url=""; 
  private static String username="";  
  private static String password="";  
  static {    
          //获得一个资源文件对象
    Properties p = new Properties();    
    try {     
            //加载资源文件
      p.load(JdbcUtils.class.getClassLoader().getResourceAsStream("jdbc.properties"));
      Driver = p.getProperty("Driver");
      url = p.getProperty("url");
      username = p.getProperty("username");
      password = p.getProperty("password");     
      //加载驱动程序
      Class.forName(Driver);
    } catch (Exception e) {
      e.printStackTrace();
    }
  } 
  private static Connection getConnection(){
    Connection conn = null;   
    try {
      conn = DriverManager.getConnection(url, username, password);
    } catch (SQLException e) {
      e.printStackTrace();
    }   return conn;
  } 
  //封装列表User
  public static List<?> getList(String sql,Class<?> clazz) {
    System.out.println(sql);
    Connection conn = null;
    PreparedStatement ps = null;
    ResultSet re = null;
    conn = getConnection();
    List<Object> list = new ArrayList(); 
    try {     
            //创建sql预编译器
      ps = conn.prepareStatement(sql);      
      //执行sql语句
      re = ps.executeQuery();     
      //从执行完成的结果中得到数据
      ResultSetMetaData data = re.getMetaData();      
      //得到数据的总列数
      int i = data.getColumnCount();      
      while(re.next()){       
              Object obj = clazz.newInstance();       
              for (int j = 1; j <=i; j++) {
          BeanUtils.copyProperty(obj, data.getColumnName(j),re.getObject(j));
        }
        list.add(obj);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }finally{
      close(conn, ps, re);
    }   
    return list;
  } 
  //修改查询
  public static Object findById(String sql,Class<?> clazz){   
          //获取数据库连接
    Connection conn = null;
    PreparedStatement ps = null;    
    Object obj = null;
    conn = getConnection();   
    try {
                ps = conn.prepareStatement(sql);
                ResultSet re = ps.executeQuery();
                ResultSetMetaData data = re.getMetaData();    
                int i = data.getColumnCount();    
                if(re.next()){
                  obj = clazz.newInstance();      
                  for (int j = 1; j <= i; j++) {
                    BeanUtils.copyProperty(obj, data.getColumnName(j), re.getObject(j));
                  }
                }
    } catch (Exception e) {
      e.printStackTrace();
    }   return obj;
  }   

  //添加/删除/修改
  public static int excute(String sql){   
          int i = 0;
    Connection conn = null;
    PreparedStatement ps = null;
    conn = getConnection();   
    try {
            ps = conn.prepareStatement(sql);
            i = ps.executeUpdate();   
            if(i>0){
              System.out.println("成功");
            }
    } catch (Exception e) {
      e.printStackTrace();
    }   
    return i;
  } 


  //封装关流
  private static void close(Connection conn,PreparedStatement ps,ResultSet re){   
          try {     
                  if(conn!=null)
              conn.close();     
      if(ps!=null)
              ps.close();     
      if(re!=null)
              re.close();
    } catch (SQLException e) {
      e.printStackTrace();
    }

  }
}