public User loadUser(User user) { String sql = "select * from user where userID = '" + user.getUserId() + "'and password = '" + user.getPassword() + "'"; System.out.println("登录的sql："+ sql); User user1 = null; try { user1 = queryRunner.query(connection, sql, new BeanHandler<>(User.class)); } catch (SQLException e) { e.printStackTrace(); } return user1; }输入用户ID为1，密码为123456，为什么显示登录的sql：select * from user where userID = 'null'and password = '123456'

根据您提供的代码，如果传入的`User`对象的`userId`属性值为`1`，则`sql`语句应该为：

select * from user where userID = '1' and password = '123456'

但是，根据您提供的信息，`sql`语句中的`userID`字段被解析为字符串`'null'`。这可能是因为传入的`User`对象的`userId`属性值不是字符串类型，而是其他类型（例如整型）。可以将`userId`属性值转换为字符串类型，例如：

public User loadUser(User user) {
    String sql = "select * from user where userID = '" + String.valueOf(user.getUserId()) + "'and password = '" + user.getPassword() + "'";
    System.out.println("登录的sql："+ sql);
    User user1 = null;
    try {
        user1 = queryRunner.query(connection, sql, new BeanHandler<>(User.class));
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return user1;
}

这样，无论传入的`User`对象的`userId`属性值是什么类型，都会被转换为字符串类型，保证`sql`语句正确解析。