JDBC ORM（Object Relationship Database Mapping）

ORM=Object Relationship Database Mapping

对象和关系数据库的映射

简单说，一个对象，对应数据库里的一条记录

示例：根据id返回一个Hero对象

提供方法get(int id)
返回一个Hero对象

public class Hero {
    //增加id属性
    public int id;
    public String name;
    public float hp;
    public int damage;
 
}

public class TestJDBC {
   
    public static Hero get(int id) {
        Hero hero = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
 
        try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8","root", "admin");
            Statement s = c.createStatement();) {
 
            String sql = "select * from hero where id = " + id;
   
            ResultSet rs = s.executeQuery(sql);
   
            // 因为id是唯一的，ResultSet最多只能有一条记录
            // 所以使用if代替while
            if (rs.next()) {
                hero = new Hero();
                String name = rs.getString(2);
                float hp = rs.getFloat("hp");
                int damage = rs.getInt(4);
                hero.name = name;
                hero.hp = hp;
                hero.damage = damage;
                hero.id = id;
            }
   
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return hero;
   
    }

    public static void main(String[] args) {
        Hero hero = get(2);
        System.out.println(hero.name+"的hp是"+hero.hp+",damage是"+hero.damage);
    }
}

 输出：

提莫的hp是313.0,damage是50