J2EE开发初步，MyEclipse+SQLServer2000插入、删除、更新、查询步骤+代码（改进版）

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上一篇中代码冗余太多，不符合Java代码重用的特点，特此改进。本次改进定义两个类：public class DBConnection和public class CRUTestByDBConnection，前者主要用于加载驱动、创建连接对象和关闭资源对象；后者用于定义sql语句、遍历结果集（如果用得到的话），来实现对数据库的各种操作。

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

public class DBConnection {
private static String driverName="com.microsoft.sqlserver.jdbc.SQLServerDriver";
private static String url="jdbc:sqlserver://localhost:1433;DataBaseName=jdbc_test";
private static String user="sa";
private static String password="sa";

    private DBConnection(){

    }
    static{
    try{
      Class.forName(driverName);
    }catch(ClassNotFoundException e){
      e.printStackTrace();
      throw new ExceptionInInitializerError(e.getMessage());
    }
    }

    public static Connection getConnection()throws SQLException{
    return DriverManager.getConnection(url,user,password);
    }

    public static void close(ResultSet rs,Statement st,Connection conn){
    try{
      if(rs!=null){
       rs.close();
      }
    }catch(SQLException e){
      e.printStackTrace();
    }finally{
      try{
       if(st!=null){
        st.close();
       }
      }catch(SQLException e){
       e.printStackTrace();
      }finally{
       if(conn!=null){
        try{
         conn.close();
        }catch(SQLException e){
         e.printStackTrace();
        }
       }
      }
    }
    }
}

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;

public class CRUTestByDBConnection {
private static Connection conn=null;
private static Statement st=null;
private static ResultSet rs=null;

public static void main(String[]args)throws SQLException{
  CRUTestByDBConnection.add();
  CRUTestByDBConnection.get();
  CRUTestByDBConnection.update();
  CRUTestByDBConnection.delete();
}

public static void add()throws SQLException{
  try{
   conn=DBConnection.getConnection();
   String sql="insert into [user](name,password,email,age,birthday,money)values('zhangsan','123','zhangsan@126.com',22,'1988-12-31',500.0)";
   st=conn.createStatement();
   st.executeUpdate(sql);
  }finally{
   DBConnection.close(rs, st, conn);
  }
}

public static void get()throws SQLException{
  try{
   conn=DBConnection.getConnection();
   String sql="select id,name,password,email,age,birthday,money from [user]";
   st=conn.createStatement();
   rs=st.executeQuery(sql);
   while(rs.next()){
    int id=rs.getInt("id");
    String name=rs.getString("name");
    String password=rs.getString("password");
    String email=rs.getString("email");
    int age=rs.getInt("age");
    Date birthday=rs.getDate("birthday");
    float money=rs.getFloat("money");
    System.out.println("id="+id+";name="+name+";password="+password+";email="+email+";age="+age+";birthday="+birthday+";money="+money);

   }
   }finally{
    DBConnection.close(rs, st, conn);
   }
}

public static void update()throws SQLException{
  try{
   conn=DBConnection.getConnection();
   String sql="update [user] set name='lisi',password='abcd',email='lisi@163.com',age=22,birthday='1988-12-21',money=1000.0 where id=4";
   st=conn.createStatement();
   st.executeUpdate(sql);
  }finally{
      DBConnection.close(rs,st,conn);
  }
}

public static void delete()throws SQLException{
  try{
   conn=DBConnection.getConnection();
   String sql="delete from [user] where id=9";
   st=conn.createStatement();
   st.executeUpdate(sql);
  }finally{
   DBConnection.close(rs, st, conn);
  }
}

}