[原创链接: http://www.smithfox.com/?e=16 转载请保留此声明, 谢谢]
绝大部分网络上对幂等性的解释类似于:
"幂等性是指重复使用同样的参数调用同一方法时总能获得同样的结果。比如对同一资源的GET请求访问结果都是一样的。"
我认为这种解释是非常错误的, 幂等性强调的是外界通过接口对系统内部的影响, 外界怎么看系统和幂等性没有关系. 就上面这种解释, System.getCPULoad(), 这两次调用返回能一样吗？ 但因为是只读接口, 对系统内部状态没有影响, 所以这个函数还是幂等性的.
首先了解一下什么是幂等性，如果你没有兴趣可以直接跳过这段代数概念解释 :)
幂等(idempotence)是来自于高等代数中的概念。
定义如下(加入了自己理解)：
单目运算, x为某集合内的任意数, f为运算子如果满足f(x)=f(f(x)), 那么我们称f运算为具有幂等性(idempotent)
比如在实数集中,绝对值运算就是一个例子: abs(a)=abs(abs(a))
双目运算，x为某集合内的任意数, f为运算子如果满足f(x,x)=x, f运算的前提是两个参数都同为x, 那么我们也称f运算为具有幂等性
比如在实数集中,求两个数的最大值的函数: max(x,x) = x,&还有布尔代数中,逻辑运算 "与", "或" 也都是幂等运算, 因为他们符合AND(0,0) = 0, AND(1,1) = 1, OR(0,0) = 0, OR(1,1) = 1
在将幂等性应用到软件开发中,需要一些更深的理解. 我的理解如下:
数学处理的是运算和数值, 程序开发中往往处理的是对象和函数. 但是我们不能简单地理解为数学幂等中的运算就是函数,而数值就是对象!!
比如有Person对象有两个属性weight和age,但是所有的function只能对其中一个属性操作. 所以从这个层面我们可以理解为: 函数只对该函数所操作的对象某个属性具有幂等性, 而不是说对整个对象有运算幂等性.
//是幂等函数
public void setAge(int v){
this.age =
//不是幂等函数
public void increaseAge(){
this.age++;
//是幂等函数
public void setWeight(int v){
this.weight=v+10;//故意加10斤!!
还有一点必须要澄清的是:&幂等性所表达的概念关注的是数学层面的运算和数值, 并没有提及到数值的安全性问题.
比如上面的Person的setAge函数, 有两种case不是幂等性所关心的, 但程序开发却又必须要关心的:
1. 两个线程同时调用
2. 因为age从业务上讲不可能递减, 如果前一次调用设置是30岁, 后一次调用变成了10岁或是更离谱的 -1&岁
所以RESTful设计中将幂等性和安全性是作为两个不同的指标来衡量POST,PUT,GET,DELETE操作的:
重要方法 安全？ 幂等？
幂等性是系统的接口对外一种承诺(而不是实现), 承诺只要调用接口成功, 外部多次调用对系统的影响是一致的. 声明为幂等的接口会认为外部调用失败是常态, 并且失败之后必然会有重试.
就象cache有cache基本实现范式一样,&幂等也有自己的固定外部调用范式
cache实现范式:
value getValue(key){
value = getValueFromCache(key);
if( value == null ){
value = readFromPersistence(key);
saveValueIntoCache(key,value);
幂等外部调用范式
client.age = 30;
while(一些退出条件){
if(socket.setPersonAge(person,client.age) == FAILED){
int newAge = socket.getPersonAge();
//处理冲突问题: 因为age只可能越来越大,所以将client的age更新为server端更大的age
if(newAge&30){
client.age = newA
//无法进行冲突解决,再次尝试
} catch(Exception){
//发生网络异常, 再次尝试
幂等接口的内部实现需要有对内保护机制, 一般情况是用类似于乐观锁的版本机制.版本重点是体现时间的先后.
[原创链接:&http://www.smithfox.com/?e=16 转载请保留此声明, 谢谢]
| Monday 27 September 2010 at 1:29 pm |
&&&&&& | Used tags:Lupe Fiasco_百度百科
声明：百科词条人人可编辑，词条创建和修改均免费，绝不存在官方及代理商付费代编，请勿上当受骗。
Lupe Fiasco
嘻哈歌手，代表作：The Show Goes On
Lupe Fiasco个人履历
Lupe Fiasco, 原名Wasalu Muhammad Jaco，于生于市. 现年34岁。音乐流派：Hip hop。现在同时是rapper，songwriter，record producer和1st&15th的CEO。
原名Wasalu Muhammad Jaco出生，是家里九位中最小的成员，父亲为非洲籍鼓手，母亲为美食，对于Hip Hop音乐的喜爱获得家里支持，早在上中学的时候就热衷于饶舌表演，以东岸街头诗人Nas为目标，其专辑It Was Written给了Lupe莫大震撼与影响。中学毕业后先是组团Da Pak并签约于Sony厂牌旗下的Epic，不久解散后又因和Jay-Z合作单曲被L.A. Reid相中并签入BMG厂牌旗下的Arista,不过他个人事业的发展却并不顺利，一直充当着，直到和主流大厂Atlantic唱片签约，在公司极为重视下全心着手筹备他的个人专辑。值得一提的是，虽然是Hip Hop歌手，但信奉伊斯兰教的Lupe，却遵守教规不去Club、不抽烟喝酒，成为乐坛的异类人物。
Lupe Fiasco社会评价
Jay-Z 觉得他歌词玩的文字游戏让人精神振奋；Twista把他看作来自的下一个说唱大明星；XXL 杂志评价他是一个在2006年与巨星们平起平坐的新秀，并且还将得到大量的称赞。 业内人士都把他看作是前途无量的新星，他就是Lupe Fiasco,一个穆斯林，高手与狂热收集者，他以一首关于滑板的说唱歌曲《Kick,Push》横空出世，不久在主流媒体开始热播，不久他的处女专辑《Food and Liquor》就广受好评。
一开始听那旋律就知道这张专辑十分特别。Lupe在中唱到“没人会做得更好”，我们听到的旋律流畅无比, 从详尽的故事讲述转换到对社会的隐喻。文字游戏如“跟一个盲人坐在一起然后给他描述什么是黄色，这十分困难”就可以让我们轻而易举的了解到Lupe为什么能得到这么多好评。 在整张专辑中各种名词动词入弹珠般迸射。《Just Might be Okay》就是一首文字游戏的代表作. 这首曲子中以恰到好处的鼓点与喇叭声为背景，Lupe 展现了他的抒情诗体“my vida loca was built like Bob Vila via God,” “now we hold the coming like contracepts” 以及“I’m cool I don’t foretell best/I ain’t nicest emcee/I ain’t Cornel West/I am Cornel Westside/Chi-Town Guevara…”
同时，Lupe在《Kick, Push》中讲述了一个惹了一身麻烦的滑板少年试图掌控自己的。这是一个令人难以置信的抒情表现。《Kick, Push 2》则是故事的续集，令人赞赏Lupe讲故事的能力. 另外《The Instrumental》是一首由Linkin Park的Mike Shinoda操刀的作品，带有明显的Mike风格，但是Lupe却用自己的歌词让这首歌有了更多的社会隐喻。.在《Hurt Me Soul》这首作品中，Lupe回顾了自己的说唱生涯，了那些对他产生影响的歌手，在曲子的最后，他还指出了这个社会的病态，唱出了他的无奈与忧虑，也是我最喜欢的作品。《I Gotcha》则是一首调侃性的歌曲，描述了各种不同类型的人，开玩笑的告诉我们“处女”与“皮条客”的原型。但是在这首歌的最后，Lupe用一些政治术语让听众重新回到严肃的状态中来。在《Real》中，Lupe深入的说明了一些街头、游戏与正义的典型问题。《American Terrorists》一看这首歌的题目就知道是一首政治性的歌曲，对美国社会进行剖析，从美国历史一直到美国的时事，表达自己的社会观，聪明的批评了美国政治的。
Lupe带着他的精神食粮，成为美国的未来。《Food and Liquor》表现了Lupe的嘻哈哲学，从爱情、社会到政治，涵盖内容十分广泛。Food是指社会的优秀，Liquor则是指社会的病态。如果你想为大脑提供些营养，这里有丰富的智识；如果你想听一些好听的旋律，这里也有适合你的节拍。这张唱片关注了社会各阶层的生活,这将使它成为经典之作。这张专辑是对人生、社会的真实反映，兼收并蓄的包含各种元素，为你提供知识与娱乐，这也是Hip-Hop的真谛。
Lupe Fiasco音乐作品
Hip-Hop Saved My Life (Feat. Nikki Jean) (Explicit Album Version)
Shining Down (Feat. Matthew Santos) [Bonus Track]
Around My Way (Freedom Ain't Free)
Daydreamin' [Feat. Jill Scott] (Explicit Album Version)
Paris, Tokyo (Explicit Album Version)
Fighters (Feat. Matthew Santos) (Explicit Album Version)
Hurt Me Soul (Explicit Album Version)
Day Dreaming
Go Go Gadget Flow (Explicit Album Version)
显示方式：专辑列表
唱片公司：1st & 15th / Atlantic
专辑曲目（12）
Letting Go
Beautiful Lasers, Two Ways
Words I Never Said
Till I Get There
State Run Radio
I Don’t Wanna Care Right Now
Break The Chain
Out Of My Head
All Black Everything
The Show Goes On
Never Forget You
专辑曲目（14）
Superstar (Feat. Matthew Santos (Live)
Bottom Top
Superstar (Fiascogate Remix)
Kick Push (Live)
Paris Tokyo (Live)
Kick Push Part 2
Can You Let Me Know
Dumb It Down (Live)
I Gotcha (Live)
Us Placers (Feat. Pharrell And Kanye West)
City Wings
Touch The Sky (Live)
Day Dreaming (Live)
Superstar (Feat. Young Jeezy & T.I.) (Remix)
唱片公司：Atlantic / Wea
专辑曲目（3）
Streets On Fire
Hi-Definition
专辑曲目（10）
Baba Says Cool for Thought
Paris, Tokyo& Deodato, Eumir/Lupe Fiasco/Soundtrakk Soundtrakk
Free Chilly& Soundtrakk Sarah Green & GemStones
Hi-Definition& Broadus, Cordozar Calvin/Shuckburgh,
Go Go Gadget Flow& Lupe Fiasco/Soundtrakk Soundtrakk
Gold Watch& Paultre, Chris/Braxton, Derrick/Lupe Fiasco Chris & Drop
The Coolest& Paultre, Chris/Braxton, Derrick/Lupe Fiasco Chris & Drop
Hip Hop Saved My Life& Lupe Fiasco/Jean, Nikki/Soundtrakk Soundtrakk Nikki Jean
Superstar& Lupe Fiasco/Soundtrakk Soundtrakk Matthew Santos
Intruder Alert& Lupe Fiasco/Soundtrakk Soundtrakk Sarah Green
Food & Liquor
专辑曲目（16）
Daydreamin
Just Might Be OK
Hurt Me Soul
Kick, Push
American Terrorist
The Instrumental
The Emperor's Soundtrack
He Say, She Say
Kick, Push II
Lupe Fiasco荣誉及奖项
BET Awards
2007, Best New Artist (nominated)
BET Hip Hop Awards
2007, Hip-Hop CD of the Year: Food & Liquor (nominated)
2007, Hip-Hop Video of the Year: &Kick Push& (nominated)
2007, Rookie of the Year: &Kick Push& (nominated)
2007, Element Award- Lyricist of the Year: (nominated)
Grammy Awards
2008, Best Urban/Alternative Performance: &Daydreamin'(feat Jill Scott)& (Winner)
2007, Best Rap Solo Performance: &Kick Push& (nominated)
2007, Best Rap Song: &Kick Push& (nominated)
2007, Best Rap Album: Food & Liquor (nominated)
Image Awards
2007, Outstanding New Artist (nominated)
MTV Video Music Awards
2008, Best Hip-Hop Video: &Superstar& feat. Matthew Santos (nominated)
Soul Train Awards
2007, Best New R&B/Soul or Rap New Artist: &I Gotcha& (nominated)
Lupe Fiasco履历及从业经历
Wasalu Muhammad Jaco (born February 17, 1982), better known by his stage name Lupe Fiasco, is a Grammy-winning American rapper. He rose to fame in 2006 following the success of his critically acclaimed debut album, Lupe Fiasco's Food & Liquor. Prominent hip hop mogul Jay-Z describes him as a &breath of fresh air& in a new hip hop world characterized by mainstream pop and glamour, a sharp contrast with the widespread lyricism-focused rap of the 1990s, and critics have called him the &Hip-Hop Generation's Next Vanguard.& [1] His second album, Lupe Fiasco's The Cool, was released on December 18, 2007.
Lupe FiascoEarly life
Born and raised on the Westside of Chicago,Wasalu Jaco is the fifth child of nine brothers and sisters. His father was an engineer, a prolific African drummer, karate teacher and owner of karate schools and army surplus stores.[3] His mother was a gourmet chef.[4] Jaco went to high school at Thornton Township High School in Harvey, Illinois.[5] He started rapping when he was in the eighth grade, but was initially put off by the vulgarity and violent imagery of his father's N.W.A..It wasn't until he heard Nas' 1996 album, It Was Written, at the age of 14 that he began to pursue hip hop music.
Growing up, Jaco was given the nickname &Lu,& the last part of his first name, by his mother. &Lupe& is an extension of this nickname, which he borrowed from a friend from high school. &Fiasco,& he says, &came from the Firm album. They had the song, 'Firm Fiasco'. I just liked the way it looked on paper.&
Lupe FiascoEarly career
By 19, Lupe Fiasco was in a group called Da Pak. They signed to Epic Records and released one single before splitting up.[6] Fiasco later signed a solo deal with Arista Records, but was dropped when president and CEO L. A. Reid was fired.[6] During this time, he had guest appearances on singles on Tha' Rayne's &Kiss Me& and &Didn't You Know& and also K Fox's 2004 &This Life.& He also released the song &Coulda Been& on a 10/03 compilation of MTV's Advance Warning.[7] He began releasing many mixtapes, developing a fan base via the internet. Just after Arista went out of business, rapper Jay-Z offered Fiasco a contract with
records. Fiasco declined having already started his own record label.
In 2004, Arista went out of business and Lupe was signed with Atlantic Records. In early 2006, Lupe and his friend and hypeman Dusean &Bishop G& Dunbar started FNF Radio, a show on the college radio station WIIT located at the Illinois Institute of Technology.
Lupe Fiasco
Lupe had gained a large underground following with the release of a series of critically acclaimed mixtapes, prominently Lupe's own Fahrenheit 1/15 Part I: The Truth Is Among Us, Fahrenheit 1/15 Part II: Revenge of the Nerds, and Fahrenheit 1/15 Part III: A Rhyming Ape. In 2005, Lupe was featured on two tracks on Mike Shinoda's solo mixtape titled Fort Minor: We Major. During this time, rapper and mogul Jay-Z heard Lupe and assisted him in the production of what would become his debut album Food & Liquor.
In 2005, Lupe app
with Kanye West
eared on the Kanye West track &Touch The Sky& from West's Late Registration. Soon after, he released his first single &Kick, Push,& a song heavily about skateboarding. As his popularity slowly increased, so did anticipation for his upcoming album Food & Liquor. The album was officially released on September 19, 2006. The album featured production from Jay-Z, Kanye West, Mike Shinoda, The Neptunes, and more. Singles from the album were &Kick, Push,& &I Gotcha& and &Daydreamin'& featuring Jill Scott. On the album &Fiasco masterfully melds his peerless storytelling gifts with his idiosyncratic passion for skateboarding, fantasy, and incisive sociopolitical commentary.&[9] The critically lauded album was later nominated for three Grammys including &Best Rap Album.& In the same year, he was voted by GQ as the &Breakout Man of the Year.&Lupe also had a small feud with skateboarder Terry Kennedy.
Lupe Fiasco2007–present
In 2007, Lupe announced his second album, &The Cool,& a concept album that expands on the story of the track of the same name on his first album. It was released on December 18, 2007 in United States. The first single and video from the album, &Superstar,& featuring Matthew Santos, was released the first week of November 2007. Baseball All-Star Ryan Braun has used &Superstar& as an at-bat song.
Also in 2007, it was revealed that Fiasco, Kanye West, and Pharrell Williams, had formed a group known as Child Rebel Soldier..As of November 2007, no projects have been announced, with Lupe noting that the members of the group were busy with solo projects and things needed to &settle down some.&However, a song made by CRS titled &US Placers,& featuring Thom Yorke, has been released.
Songs from &The Cool& are featured in the movie Street Kings. The songs &Put You on Game& and &Little Weapon& both appear in the latest trailer.
In 2008, Lupe and his band 1500 or Nothin joined Kanye's Glow in the Dark Tour, which also features Rihanna and N.E.R.D. The tour will stop in several cities, including his hometown of Chicago. He's been made #7 as the Hottest MCs in the Game of 2008 by MTV.
Lupe recently announced that he was remixing The Cool with French house act Justice.
Lupe FiascoVentures
Fiasco is the co-founder and vice-president of 1st & 15th Entertainment, a record label under Atlantic.However, due to the recent arrest and imprisonment of co-founder, CEO, and partner Charles &Chilly& Patton, Fiasco now serves as the current CEO. In January 2006, Lupe signed with major footwear and apparel corporation Reebok becoming part of the &O.G& marketing campaign, where rap artists such as Lil Wayne and Mike Jones designed their own personal colorway of the Reebok &O.G& model.He designed a white/grey model of the shoe.
Lupe FiascoPersonal life
Lupe FiascoReligion
Lupe has been open about his Islamic faith. He has noted the importance of religion in his life, stating: &Well, I was born Muslim, so Islam plays a part in my life and everything I do, to a certain extent. I'm not like the poster boy for Islam... I still got my flaws and stuff like that, so I don't really wear that on my sleeve... I don't go to clubs, I don't drink, I don't smoke, you know like my whole - the whole groupie situation is shut down.& The front of Lupe's The Cool album cover is stylized to look like that of Persian calligraphy. Along with this, Lupe begins Food & Liquor by reciting an Islamic prayer: A'uzu billahi min ash shaitani r rajimi Bismi 'llahi 'r-rahmani 'r-rahim, which translates to &I seek refuge with Allah from Satan, the rejected. In the name of Allah, the Most Gracious, Ever Merciful.&
Lupe FiascoInfluences
Lupe is highly influenced by Crucial Conflict, Kanye West, 8Ball & MJG, Spice 1 and Nas among others. Lupe regards It Was Written as his favorite album and cites it as his primary source of inspiration. Lupe is also an avid skateboarder, which influenced his debut single &Kick, Push.& Lupe is also heavily influenced by Japanese-anime/ he has referenced the following anime shows in his lyrics: Lupin the 3rd (in Kanye West's Touch The Sky), Transformers/Gundam (in Daydreamin'), and Trigun (in various songs). Furthermore Lupe Fiasco also takes influence from videogames, which he occasionally references in his songs. This is particularly apparent in the song, &Jedi Mind Tricks& where Lupe states &the boy game advance, come peep the genesis, I broke bread with society's menaces.& A reference to the portable Nintendo console the Gameboy Advance, and the Sega Genesis co
nsole. Lupe Fiasco makes another reference to Sega in the single &I Gotcha&; where he references the company's mascot &Sonic the Hedgehog&. This can be seen in a line from the song that states, & I love my city really hope that God bless it, have my mind moving faster than that hog in the hedges&. Further adding to the videogame-based content that Lupe puts into his lyrics, and derives influence from is Squaresoft's Final Fantasy series, which is seen referenced in the song &And He Gets The Girl...& (which used a sample from N.E.R.D's song &Maybe&); from the &I Gotcha& single. This is evidenced by a line in the song that states, &I love Final Fantasy, I hate first-person shooters, Meteora was nice, but I bought Hybrid Theory twice&. Lastly Lupe Fiasco's influence from the videogame realm can be seen in his references to Capcom's Street Fighter videogame series (which Lupe Fiasco is quite fond of). This can be seen in a line from the song &Gold Watch& &I like Street Fighter 2 I just really hate Vega only Ken and Ryu, I find it hard to beat Blanka&. Lupe Fiasco's love, and influence of videogames is also conveyed in his rumored final album, &LupEnd& the spelling and titling of which is similar to the format of several &endgame& videogame screens (particularly 8-bit third generation, and 16-bit fourth generation videogames). Lupe Fiasco also derives inspiration from a variey of other sources like: comic book culture (particularly Japanese manga, a sentiment expressed in &Gold Watch&; and the Marvel Comics series X-Men which was referenced in the official &Superstar& remix), films (particularly Revenge Of The Nerds, and Star Wars, of which he has several underground mixtapes as well as songs named after), different forms of art (specifically Yate-born and social commentary driven graffiti artist B who Fiasco references in his song &I Gotcha&), and lastly German philosopher Friedrich Nietzsche.
同时，Lupe Fiasco百度贴吧已经开通，希望喜欢lupe的朋友多去交流灌水。sunny c0l0rway是什么意思_百度知道
sunny c0l0rway是什么意思
sunny colorway亮色的色彩设计sunny ['sʌnɪ] adj. 阳光充足的，亮色的望采纳 谢谢
采纳率：94%
为您推荐：
其他类似问题
sunny的相关知识
换一换
回答问题，赢新手礼包
个人、企业类
违法有害信息,请在下方选择后提交
色情、暴力
我们会通过消息、邮箱等方式尽快将举报结果通知您。相关词典网站：colorway是什么意思
colorway是什么意思
09-08-06 &匿名提问
请登录后再发表评论!