.NET：可擴展的單據編號生成器 + 簡單的解釋器

背景

在企業應用中單據編號的自定義是一個很常見的需求，能不能抽象一個通用的框架呢？之前寫個一篇自定義密碼強度的博文，感覺他們兩個思路應該很相似。就讓我們試試吧。

思路

這里的難點在於實現"解釋器"，比如將"前綴_<日期:yyyy_MM_dd>"解釋為“工號生成器”，而且“解釋器”的“規則”允許動態增加。

 

實現

代碼下載

類圖

核心代碼

CodeRuleGenerator.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.Text.RegularExpressions;

namespace EntityCodeRuleDemo
{
    public sealed class CodeRuleGenerator : ICodeRuleGenerator
    {
        private readonly IEnumerable<ICodeRuleProvider> _providers = new List<ICodeRuleProvider>();

        internal CodeRuleGenerator(IEnumerable<ICodeRuleProvider> providers)
        {
            _providers = providers;
        }

        public string Generate(object entity)
        {
            var sb = new StringBuilder();

            foreach (var provider in _providers)
            {
                sb.Append(provider.Generate(entity));
            }

            return sb.ToString();
        }
    }
}

CodeRuleInterpreter.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.Text.RegularExpressions;

using EntityCodeRuleDemo.RuleProviders;

namespace EntityCodeRuleDemo
{
    public static class CodeRuleInterpreter
    {
        private static Dictionary<Regex, Func<string, ICodeRuleProvider>> _providerFactorys = new Dictionary<Regex, Func<string, ICodeRuleProvider>>();

        static CodeRuleInterpreter()
        {
            SetProviderFactory(new Regex("^[^<].*?[^>]?$"), LiteralRuleProvider.LiteralRuleProviderFactory);
            SetProviderFactory(new Regex("^<日期(:(?<格式>.*?))?>$"), DateRuleProvider.DateRuleProviderFactory);
            SetProviderFactory(new Regex("^<屬性(:(?<名稱>.*?))?>$"), PropertyRuleProvider.PropertyRuleProviderFactory);
        }

        public static void SetProviderFactory(Regex regex, Func<string, ICodeRuleProvider> providerFactory)
        {
            _providerFactorys[regex] = providerFactory;
        }


        public static ICodeRuleGenerator Interpret(string codeRule)
        {
            var providers = GetProviders(codeRule);

            return new CodeRuleGenerator(providers);
        }

        private static IEnumerable<ICodeRuleProvider> GetProviders(string codeRule)
        {
            var literals = codeRule.Replace("<", "$<").Replace(">", ">$").Split('$');

            return literals
                .Where(x => !string.IsNullOrEmpty(x))
                .Select(GetProvider)
                .ToList();
        }

        private static ICodeRuleProvider GetProvider(string literal)
        {
            var providerFactory = _providerFactorys
                .FirstOrDefault(x => x.Key.IsMatch(literal))
                .Value;

            if (providerFactory == null)
            {
                throw new FormatException("格式化錯誤");
            }

            return providerFactory(literal);
        }
    }
}

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EntityCodeRuleDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            var employeeCode = CodeRuleInterpreter
                .Interpret("前綴_<日期:yyyy_MM_dd>_<屬性:NamePinYin>")
                .Generate(new Employee { NamePinYin = "DUANGW" });

            Console.WriteLine(employeeCode);
        }
    }

    class Employee
    {
        public string NamePinYin { get; set; }
        public string EmployeeCode { get; set; }
    }
}

運行效果

備注

按照這種思路，基本上能滿足企業應用的多數編碼規則要求。在真實的項目中，這些規則是要持久化到數據庫的，這樣就可以做到運行時動態的修改規則了。