連接數據庫步驟的簡單代碼

連接數據庫步驟的簡單代碼

/**

• 實體類
  */
  public class User {

  //主鍵
  private Integer userid;
  //用戶名
  private String username;
  //密碼
  private String password;

  public Integer getUserid() {
  return userid;
  }

  public void setUserid(Integer userid) {
  this.userid = userid;
  }

  public String getUsername() {
  return username;
  }

  public void setUsername(String username) {
  this.username = username;
  }

  public String getPassword() {
  return password;
  }

  public void setPassword(String password) {
  this.password = password;
  }

  @Override
  public String toString() {
  return “User{” +
  “userid=” + userid +
  “, username=” + username +
  “, password=” + password +
  ‘}’;
  }
  }

/**

• 執行代碼的先後順序
  */
  public class UserController {

  /**

  • 查詢

  • @return
    */
    public List select() {

    Connection connection = null;
    PreparedStatement ps = null;
    ResultSet rs = null;

    ArrayList users = new ArrayList();
    //1.加載驅動
    try {
    Class.forName(“com.mysql.jdbc.Driver”);

     //2.建立連接
     connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/newsdb_month", "root", "123");
     //3.執行sql返回結果
     String sql = "select * from user";
     ps = connection.prepareStatement(sql);
     rs = ps.executeQuery();
    
     //4.處理結果集
     while (rs.next()) {
         User user = new User();
         user.setUserid(rs.getInt("userid"));
         user.setUsername(rs.getString("username"));
         user.setPassword(rs.getString("password"));
         users.add(user);
     }
     return users;
    

    } catch (ClassNotFoundException e) {
    e.printStackTrace();
    } catch (SQLException e) {
    e.printStackTrace();
    } finally {
    //5.釋放資源
    try {
    connection.close();
    ps.close();
    rs.close();
    } catch (SQLException e) {
    e.printStackTrace();
    }
    }
    return null;
    }

}