java基础——数据库ORM操作原型

喜欢ヅ旅行 2023-07-02 08:28 106阅读 0赞

package jdbc;
    
    import java.sql.*;
    import java.util.ArrayList;
    import java.util.List;
    
    public class TestJDBC { 
        public static Hero get(int id) { 
            Hero hero = null;
    
            try { 
                Class.forName("com.mysql.cj.jdbc.Driver");
            } catch (ClassNotFoundException e) { 
                e.printStackTrace();
            }
    
            try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8" +
                            "&useSSL=false&serverTimezone=UTC",
                    "root", "123");
                 Statement s = c.createStatement();
            ) { 
                String sql = "select * from hero where id = "+id;
                ResultSet rs = s.executeQuery(sql);
                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) { 
                e.printStackTrace();
            }
            return hero;
        }
    
        public static void add(Hero h) { 
            try { 
                Class.forName("com.mysql.cj.jdbc.Driver");
            } catch (ClassNotFoundException e) { 
                e.printStackTrace();
            }
            String sql = "insert into hero values(null,?,?,?)";
            try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8" +
                            "&useSSL=false&serverTimezone=UTC",
                    "root", "123");
                 PreparedStatement ps = c.prepareStatement(sql);
            ) { 
                ps.setString(1,h.name);
                ps.setFloat(2,h.hp);
                ps.setInt(3,h.damage);
    
                ps.execute();
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    
        public static void delete(Hero h) { 
            try { 
                Class.forName("com.mysql.cj.jdbc.Driver");
            } catch (ClassNotFoundException e) { 
                e.printStackTrace();
            }
            String sql = "delete from hero where id = ?";
            try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8" +
                            "&useSSL=false&serverTimezone=UTC",
                    "root", "123");
                 PreparedStatement ps = c.prepareStatement(sql);
            ) { 
                ps.setInt(1,h.id);
                ps.execute();
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    
        public static void update(Hero h) { 
            try { 
                Class.forName("com.mysql.cj.jdbc.Driver");
            } catch (ClassNotFoundException e) { 
                e.printStackTrace();
            }
            String sql = "update hero set name = ?,hp = ?,damage = ? where id = ?";
            try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8" +
                            "&useSSL=false&serverTimezone=UTC",
                    "root", "123");
                 PreparedStatement ps = c.prepareStatement(sql);
            ) { 
                ps.setString(1,h.name);
                ps.setFloat(2,h.hp);
                ps.setInt(3,h.damage);
                ps.setInt(4,h.id);
                ps.execute();
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    
        public static List<Hero> list() { 
            List<Hero> heros = new ArrayList<>();
            try { 
                Class.forName("com.mysql.cj.jdbc.Driver");
            } catch (ClassNotFoundException e) { 
                e.printStackTrace();
            }
            try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8" +
                            "&useSSL=false&serverTimezone=UTC",
                    "root", "123");
                 Statement s = c.createStatement();
            ) { 
                String sql = "select * from hero";
                ResultSet rs = s.executeQuery(sql);
                while(rs.next()){ 
                    Hero hero = new Hero();
                    int id = rs.getInt(1);
                    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;
                    heros.add(hero);
                }
            } catch (SQLException e) { 
                e.printStackTrace();
            }
            return heros;
        }
    
    
    
        public static void main(String[] args){ 
            List<Hero> heros = list();
            System.out.println("数据库多少条数据："+heros.size());
    
            /*Hero h = get(27); System.out.println(h.name);*/
            /*Hero h1 = new Hero(); h1.name = "test hero"; h1.hp = 3123f; h1.damage = 233; add(h1);*/
            //delete(h);
            /*h.name = "new name"; update(h);*/
        }
    }