JDBC原理

   JDBC定义了一组操作数据库的接口，不同的数据库厂商提供了JDBC接口的实现，这个实现称为JDBC驱动。这样就可以通过JDBC接口来对不同数据库获得统一的操作。

 

JDBC常用类

1. java.sql.DriverManager: 管理一组 JDBC 驱动程序的基本服务。 2. java.sql.Connection: 与特定数据库的连接（会话）。 3. java.sql.Statement: 用于执行静态 SQL 语句并返回它所生成结果的对象。 4. java.sql.ResultSet: 表示数据库结果集的数据表，通常通过执行查询数据库的语句生成。 5. java.sql.PreparedStatement

6. java.sql.CallableStatement

 

JDBC操作数据库的一般步骤

本人封装的简单JDBC工具类SqlBean

package can.javaBean; 
import java.sql.*; 

public  class sqlBean { 
         public    Connection conn =  null; 
         public    Statement stmt =  null; 
         public    ResultSet rs =  null; 
         
         public  boolean connectDB(String DatabaseDriver, String url) {        
                conn =  null; 
                 
                 //打开数据库连接 
                 try { 
                        Class.forName(DatabaseDriver);    
                        conn = DriverManager.getConnection(url); 
                         return  true;                        
                } catch(ClassNotFoundException ex) { 
                        ex.printStackTrace(); 
                } catch(SQLException ex) { 
                        ex.printStackTrace(); 
                } 
                 return  false; 
        } 
         
         public  boolean closeConn() { 
                 //关闭数据库连接 
                 try{ 
                         if(stmt !=  null){ 
                                stmt.close(); 
                                stmt =  null; 
                        } 
                         
                         if(conn !=  null){ 
                                conn.close(); 
                                conn =  null; 
                        } 
                         return  true; 
                } catch(SQLException ex) { 
                        ex.printStackTrace(); 
                         return  false; 
                } 
        } 
         
         public ResultSet execQuery(String sql) { 
                 //执行查询 
                rs =  null; 
                 if (conn !=  null && sql !=  null) { 
                         try{ 
                                stmt = conn.createStatement(); 
                                rs = stmt.executeQuery(sql); 
                        } catch(SQLException ex)        { 
                                ex.printStackTrace(); 
                        } 
                } 
                 return rs; 
        } 
         
         public  int execUpdate(String sql) { 
                 //执行更新或删除 
                 int rows = 0; 
                 
                 if (conn !=  null && sql !=  null){ 
                         try{ 
                                stmt = conn.createStatement(); 
                                rows = stmt.executeUpdate(sql); 
                        } catch(SQLException ex)        { 
                                ex.printStackTrace(); 
                        } 
                } 
                 return rows; 
        } 
}

web.xml相应设置

<context-param>        
         <param-name>context/driver</param-name>        
         <param-value>com.mysql.jdbc.Driver</param-value> 
         <param-name>context/url</param-name> 
         <param-value><![CDATA[jdbc:mysql: //localhost/teachingSystem?user=canny&password=123456&useUnicode=true&characterEncoding=GB2312]]></param-value> 
</context-param> 

servlet使用例子

doPost()