Groovy DSL （1） Command chains

Groovy可以方便的制作DSL，Command chain是支持它这么做的一个特性。
简单说，就是方法调用用约定好的规则省略括号和“ . ”等操作符，下面看例子

// equivalent to: turn(left).then(right)turn left then right       ** 这里省略了括号和点，一个方法间隔一个参数，当然，后面的方法是前面方法的返回值 **// equivalent to: take(2.pills).of(chloroquinine).after(6.hours)take 2.pills of chloroquinine after 6.hours         这里规则是相同的，参数不同// equivalent to: paint(wall).with(red, green).and(yellow)paint wall with red, green and yellow               这里展示多个参数的例子，即用逗号隔开// with named parameters too// equivalent to: check(that: margarita).tastes(good)check that: margarita tastes good                 参数为属性// with closures as parameters// equivalent to: given({}).when({}).then({})given { } when { } then { }                      参数为闭包// equivalent to: select(all).unique().from(names)select all unique() from names                   没有参数的用空括号// equivalent to: take(3).cookies// and also this: take(3).getCookies()take 3 cookies                                  如果一行共有奇数个词，则最后是属性调用

下面是一些实例：

show = { println it }square_root = { Math.sqrt(it) }def please(action) {  [the: { what ->    [of: { n -> action(what(n)) }]             创造DSL有很多方式，这里用map和闭包做的  }]}// equivalent to: please(show).the(square_root).of(100)please show the square_root of 100// ==> 10.0

下面例子是调用第三方包，或你自己实现的代码库来做DSL

@Grab('com.google.guava:guava:r09')import com.google.common.base.*def result = Splitter.on(',').trimResults(CharMatcher.is('_' as char)).split("_a ,_b_ ,c__").iterator().toList()                      调用了Google的guava库的splitter方法@Grab('com.google.guava:guava:r09')import com.google.common.base.*def split(string) {  [on: { sep ->    [trimming: { trimChar ->      Splitter.on(sep).trimResults(CharMatcher.is(trimChar as    char)).split(string).iterator().toList()    }]  }]                                                   继续用map和闭包做DSL}def result = Splitter.on(',').trimResults(CharMatcher.is('_' as char)).split("_a ,_b_ ,c__").iterator().toList()                           正常调用def result = split "_a ,_b_ ,c__" on ',' trimming '_\'         等价于这个