数据库操作，jdbc的CRUD

 1 public class DBUtil {
 2 
 3     public static String URL = "jdbc:mysql://localhost:3306/JDBCDEmo";
 4     public static String USER = "root";
 5     public static String PASSWORD = "abc123_";
 6     
 7     private static Connection conn;
 8     
 9     static{
10         try {
11             //或得去驱动
12             Class.forName("com.mysql.jdbc.Driver");
13             //得到数据库的连接
14             conn = DriverManager.getConnection(URL, USER, PASSWORD);
15         } catch (Exception e) {
16             // TODO Auto-generated catch block
17             e.printStackTrace();
18         }
19     }
20     
21     public static Connection getConnection(){
22         return conn;
23     }46 }

public void addBoy(Boy by) {
　　　　　　//或得连接，编写sql语句，？号代表要插入额数据
        Connection conn = DBUtil.getConnection();
        String sql = "INSERT INTO Boy" + " (user_name, sex, age, birthday, email, mobile, create_user, "
                + "create_date, update_user, update_date, isdel)"
                + " values(?, ?, ?, ?, ?, ?, ?, current_date(), ?, current_date(), ?)";
        try {
1.PreparedStatement是预编译的,对于批量处理可以大大提高效率. 也叫JDBC存储过程
2.使用 Statement 对象。在对数据库只执行一次性存取的时侯，用 Statement 对象进行处理。PreparedStatement 对象的开销比Statement大，对于一次性操作并不会带来额外的好处。
3.statement每次执行sql语句，相关数据库都要执行sql语句的编译，preparedstatement是预编译得, preparedstatement支持批处理
关于是使用PrepareStatement还是普通的statement 请参考这里 http://www.cnblogs.com/0banana0/articles/2029863.html

            PreparedStatement pst = conn.prepareStatement(sql);
            pst.setString(1, by.getUser_name());
            pst.setInt(2, by.getSex());
            pst.setInt(3, by.getAge());
            pst.setDate(4, new Date(by.getBirthday().getTime()));
            pst.setString(5, by.getEmail());
            pst.setString(6, by.getMobile());
            pst.setString(7, by.getCreate_user());
            pst.setString(8, by.getUpdate_user());
            pst.setInt(9, by.getIsdel());
            pst.execute();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
//修改
    public void updateBoy(Boy by){
        Connection conn = DBUtil.getConnection();
        String sql = "Update Boy set " + " user_name = ?, sex = ?, age = ?, birthday = ?, email = ?, mobile = ?, create_user = ?, "
                + "create_date = current_date(), update_user = ?, update_date = current_date(), isdel = ?"
                + " where id = ?";
        try {
            PreparedStatement pst = conn.prepareStatement(sql);
            pst.setString(1, by.getUser_name());
            pst.setInt(2, by.getSex());
            pst.setInt(3, by.getAge());
            pst.setDate(4, new Date(by.getBirthday().getTime()));
            pst.setString(5, by.getEmail());
            pst.setString(6, by.getMobile());
            pst.setString(7, by.getCreate_user());
            pst.setString(8, by.getUpdate_user());
            pst.setInt(9, by.getIsdel());
            pst.setInt(10, by.getId());
            pst.execute();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    public void deleteBoy(Boy by) throws Exception{
        Connection conn = DBUtil.getConnection();
        String sql ="DELETE FROM Boy"    + " where id = ?";
            PreparedStatement pst = conn.prepareStatement(sql);
            pst.setInt(1, by.getId());
            pst.execute();
    }

    public List<Boy> queray() {
        List<Boy> list = new ArrayList<>();
        try {
            Connection conn = DBUtil.getConnection();
            Statement sm = conn.createStatement();
　　　　　　//需要获得 结果操作集，之后就可以得到查询出来的结果 .next()是判断有没有结果，并把操作集的指针移到下一个操作集上。其实查询出来的结果可以看做是数据库中的一行一行的数据，那么刚开始的时候指针指向数据表的上一行，好比一个空的头指针，所以要移到下一个，以判断到底有没有数据。
            ResultSet rs = sm.executeQuery("SELECT user_name FROM Boy");
            while (rs.next()) {
                String name = rs.getString("user_name");
                Boy by = new Boy();
                by.setUser_name(name);
                list.add(by);
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return list;

    }
}