JAVA高级面试进阶训练营视频教程

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/// <summary>
    /// ef实现withnolock，给表名后面添加with(nolock)，不适用.net core
    /// </summary>
    public class WithNoLockInterceptor : DbCommandInterceptor
    {
        private static readonly Regex TableAliasRegex = new Regex(@"(?<tableAlias>\[dbo\].\[\w+\] AS \[Extent\d+\](?! WITH\(NOLOCK\)))", RegexOptions.Multiline | RegexOptions.IgnoreCase);

        /// <summary>
        /// https://www.bbsmax.com/A/8Bz8V6V65x/
        /// 建议不要为标记为 ThreadStaticAttribute 的字段指定初始值，因为这样的初始化只会发生一次，因此在类构造函数执行时只会影响一个线程。
        /// 在不指定初始值的情况下，如果它是值类型，可依赖初始化为其默认值的字段，如果它是引用类型，则可依赖初始化为空引用的字段。
        /// </summary>
        [ThreadStatic]
        public static bool Uselocking;

        [ThreadStatic]
        public static string CommandText;

        public override void ScalarExecuting(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
        {
            if (!Uselocking)
            {
                command.CommandText = TableAliasRegex.Replace(command.CommandText, "${tableAlias} WITH(NOLOCK) ");
                CommandText = command.CommandText;
            }
            //System.IO.File.AppendAllText("D:\\1.txt", "Uselocking=" + Uselocking.ToString() + "~" + CommandText + "\r\n\r\n");
        }

        public override void ReaderExecuting(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
        {
            if (!Uselocking)
            {
                command.CommandText = TableAliasRegex.Replace(command.CommandText, "${tableAlias} WITH(NOLOCK) ");
                CommandText = command.CommandText;
            }
            //System.IO.File.AppendAllText("D:\\1.txt", "Uselocking=" + Uselocking.ToString() + "~" + CommandText + "\r\n\r\n");
        }

使用：在Global.cs的Application_Start()里面添加如下语句，生成的sql会自动加上with(nolock)

//ef命令拦截器
DbInterception.Add(new WithNoLockInterceptor());

如果执行的sql语句需要锁表，增加如下扩展即可

public static class WithNoLockExtensions
    {
        /// <summary>
        /// 部分查询需要使用锁查询的，可以调用此扩展（默认全局查询使用with(nolock)）
        /// 参考：https://github.com/aspnetboilerplate/aspnetboilerplate/issues/1637/
        /// 示例：
        /// 1、query.OrderByCustom(filters.orderFields).Select({...}).UseLocking(querable => querable.PagingAsync(filters.page, filters.rows));
        /// 2、repository.EntitiesAsNoTracking.Select(...).UseLocking(item=>item.FirstOrDefaultAsync());
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="query"></param>
        /// <param name="queryAction"></param>
        /// <returns></returns>
        public static TResult UseLocking<T, TResult>(this IQueryable<T> query, Func<IQueryable<T>, TResult> queryAction)
        {
            WithNoLockInterceptor.Uselocking = true;
            //System.IO.File.AppendAllText("D:\\2.txt", $"更改了Uselocking{WithNoLockInterceptor.Uselocking}状态\r\n\r\n");

            TResult queryableResult = default(TResult);
            try
            {
                queryableResult = queryAction(query);
            }
            finally
            {
                WithNoLockInterceptor.Uselocking = false;
            }

            //System.IO.File.AppendAllText("D:\\2.txt", $"更改了Uselocking2{WithNoLockInterceptor.Uselocking}状态\r\n\r\n");
            return queryableResult;
        }

 

 

1、修复了网上提供的正则表达式特殊情况下报错问题