J2EE中连接SQL2000数据库

   首先我们在与数据库连接中应该注意几个问题：1 不允许重复取值 如：

   ResultSet rs = stmt.executeQuery(sql);

   if(rs.next())

   {

       System.out.printlin("name");

       System.out.printlin("name");

   }

  像这种取值方式就是错误的

   2:取值过程中不允许乱序取值 如：

   ResultSet rs = stmt.executeQuery(sql);

   if(rs.next())

   {

       System.out.printlin(1);

       System.out.printlin(3);

       System.out.printlin(2);

   }

   这种乱序取值也是错误不可取的

   3:不允许交叉

 

其次，写出正确的JAVA中连接数据库的方法类

 

先建立一个com.viita.common的包，在包里面建立 BaseDao.java 数据库基本操作类

 

 

 

 

  

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class BaseDao {
    private Connection conn = null;
    private Statement stmt = null;
    private ResultSet rs = null;
    
    public BaseDao()
    {
        try {
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            conn = DriverManager.getConnection("jdbc:odbc:test");
     stmt = conn.createStatement();
        } catch (Exception e) {
            // TODO Auto-generated catch block

            e.printStackTrace();
        }
        
    }
    
    public void executeUpdate(String sql) throws SQLException
    {
        stmt.executeUpdate(sql);
        System.out.println(sql);
    }
    
    
    public ResultSet executeQuery(String sql) throws SQLException
    {
        rs = stmt.executeQuery(sql);
        return rs;
    }
    
    
    public void close()
    {
        try {
            if(rs!=null)
                rs.close();
        } catch (Exception e) {
            // TODO: handle exception

            System.out.println(e);
        }
        try {
            if(stmt!=null)
                stmt.close();
        } catch (Exception e) {
            // TODO: handle exception

            System.out.println(e);
        }
        try {
            if(conn!=null)
                conn.close();
        } catch (Exception e) {
            // TODO: handle exception

            System.out.println(e);
        }
    }
    
    
    
    public static void main(String[] args) throws Exception {
        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
        Connection conn = DriverManager.getConnection("jdbc:odbc:Driver={MicroSoft Access Driver (*.mdb)};DBQ=C:\\accp.mdb","","");
        Statement stmt = conn.createStatement();
        
        String sql = "insert into userinfo (userName,passWord,sex,age,address) values ('zs','zs','female','2','accp')";
        stmt.executeUpdate(sql);
        conn.close();
    }
    
    
    
}


 

接着我们建立com.viita.dao包，里面放 用来操作数据库增 删 改 查 等方法的类baseDao.java

 

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.accp.bean.UserinfoBean;
import com.accp.common.BaseDao;

public class UserinfoDao {

    //插入方法
    public void saveUserinfo(UserinfoBean userinfo) throws SQLException
    {
        String sql = "insert into ...";
        BaseDao db = new BaseDao();
        try {
            db.executeUpdate(sql);
        } catch (SQLException e) {
            // TODO Auto-generated catch block

            throw new SQLException("数据库操作错误:"+e);
        }finally
        {
            db.close();
        }
    }

        //获取数据库信息
         public List getUserinfos()
       {
        List list = new ArrayList();
        String sql = "select * from ...";
        BaseDao db = new BaseDao();
        ResultSet rs;
        try {
            rs = db.executeQuery(sql);
            while(rs.next())
            {
                UserinfoBean bean = new UserinfoBean();
                bean.setId(rs.getInt(1));
                .......                list.add(bean);
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block

            e.printStackTrace();
        }finally
        {
            db.close();
        }
        
        return list;
    }
}


 

这样 就基本上完成了J2EE中对数据库的标准操作 切记：执行完方法必须关闭数据库的链接！