Groovy基本句法
Groovy基本句法
Gradle作为一个构建工具自然不会自己去创造一门语言来支撑自己，那么它用的是哪门子语言呢？什么语言能写成这样：
task hello {
doLast {
println 'Hello world!'
}
}
如此风骚的语法自然要归Groovy莫属了。
什么是Groovy
官方介绍如下：
Apache Groovy is a powerful, optionally typed and dynamic language, with static-typing and static compilation capabilities, for the Java platform aimed at improving developer productivity thanks to a concise, familiar and easy to learn syntax. It integrates smoothly with any Java program, and immediately delivers to your application powerful features, including scripting capabilities, Domain-Specific Language authoring, runtime and compile-time meta-programming and functional programming.
大概意思是Groovy是一门运行在java平台上的强大的、可选类型的、动态语言。使用Groovy可以使你的应用具备脚本，DSL定义，运行时和编译时元编程，函数式编程等功能。
接下来将分几个小节简单介绍Groovy的语法规范。
Groovy语法
注释
Groovy使用的注释有一下几种：
1.单行注释
// a standalone single line comment
println "hello" // a comment till the end of the line
2.多行注释
/* a standalone multiline comment
spanning two lines */
println "hello" /* a multiline comment starting
at the end of a statement */
println 1 /* one */ + 2 /* two */
3.文档注释
/**
* A Class description
*/
class Person {
/** the name of the person */
String name
/**
* Creates a greeting method for a certain person.
*
* @param otherPerson the person to greet
* @return a greeting message
*/
String greet(String otherPerson) {
"Hello ${otherPerson}"
}
}
4.组织行
#!/usr/bin/env groovy
println "Hello from the shebang line"
这类脚本注释主要用于表明脚本的路径。
字符串
单引号字符串
单引号字符串对应java中的String，不支持插入。
'a single quoted string'
字符串连接
assert 'ab' == 'a' + 'b'
三引号字符串
'''a triple single quoted string'''
三引号字符串同样对应java中的String，不支持动态插入。三引号字符串支持多行：
def aMultilineString = '''line one
line two
line three'''
转义
Groovy中使用\来进行转义
'an escaped single quote: \' needs a backslash'
双引号字符串
"a double quoted string"
如果双引号字符串中没有插入表达式的话对应的是java中的String对象，如果有则对应Groovy中的GString对象。
Groovy中使用${}来表示插入表达式，$来表示引用表达：
def name = 'Guillaume' // a plain string
def greeting = "Hello ${name}"
assert greeting.toString() == 'Hello Guillaume'
def person = [name: 'Guillaume', age: 36]
assert "$person.name is $person.age years old" == 'Guillaume is 36 years old'
shouldFail(MissingPropertyException) {
println "$number.toString()"
}
插入闭包表达式
def sParameterLessClosure = "1 + 2 == ${-> 3}"
assert sParameterLessClosure == '1 + 2 == 3'
def sOneParamClosure = "1 + 2 == ${ w -> w << 3}"
assert sOneParamClosure == '1 + 2 == 3'
def number = 1
def eagerGString = "value == ${number}"
def lazyGString = "value == ${ -> number }"
assert eagerGString == "value == 1"
assert lazyGString == "value == 1"
number = 2
assert eagerGString == "value == 1"
assert lazyGString == "value == 2"
关于闭包，暂时先看看就行，等后面具体学习完闭包以后再回来看这几个表达式就简单了。
三双引号字符串
def name = 'Groovy'
def template = """
Dear Mr ${name},
You're the winner of the lottery!
Yours sincerly,
Dave
"""
assert template.toString().contains('Groovy')
斜杠字符串
Groovy也可以使用/来定义字符串，主要用于正则表达式
def fooPattern = /.*foo.*/
assert fooPattern == '.*foo.*'
def escapeSlash = /The character \/ is a forward slash/
assert escapeSlash == 'The character / is a forward slash'
def multilineSlashy = /one
two
three/
assert multilineSlashy.contains('\n')
def color = 'blue'
def interpolatedSlashy = /a ${color} car/
assert interpolatedSlashy == 'a blue car'
\(/和/\)字符串
def name = "Guillaume"
def date = "April, 1st"
def dollarSlashy = $/
Hello $name,
today we're ${date}.
$ dollar sign
$$ escaped dollar sign
\ backslash
/ forward slash
$/ escaped forward slash
$/$ escaped dollar slashy string delimiter
/$
assert [
'Guillaume',
'April, 1st',
'$ dollar sign',
'$ escaped dollar sign',
'\\ backslash',
'/ forward slash',
'$/ escaped forward slash',
'/$ escaped dollar slashy string delimiter'
].each { dollarSlashy.contains(it) }
字符
单引号字符串如果只有一个字符会被转化成char类型。
列表
Groovy中列表使用[]表示，其中可以包含任意类型的元素：
def heterogeneous = [1, "a", true]
使用下标进行取值和赋值
def letters = ['a', 'b', 'c', 'd']
assert letters[0] == 'a'
assert letters[1] == 'b'
assert letters[-1] == 'd'
assert letters[-2] == 'c'
letters[2] = 'C'
assert letters[2] == 'C'
letters << 'e'
assert letters[ 4] == 'e'
assert letters[-1] == 'e'
assert letters[1, 3] == ['b', 'd']
assert letters[2..4] == ['C', 'd', 'e']
数组
Groovy中复用List来充当数组，但如果要明确定义真正的数组需要使用类似java的定义方法
String[] arrStr = ['Ananas', 'Banana', 'Kiwi']
assert arrStr instanceof String[]
assert !(arrStr instanceof List)
def numArr = [1, 2, 3] as int[]
assert numArr instanceof int[]
assert numArr.size() == 3
键值数组
Groovy中键值数组使用如下
def colors = [red: '#FF0000', green: '#00FF00', blue: '#0000FF']
assert colors['red'] == '#FF0000'
assert colors.green == '#00FF00'
colors['pink'] = '#FF00FF'
colors.yellow = '#FFFF00'
assert colors.pink == '#FF00FF'
assert colors['yellow'] == '#FFFF00'
assert colors instanceof java.util.LinkedHashMap
以上简单列举了Groovy的基本语法，想要深入学习的可以参考以下网址：
运行syntax.groovy查看实例及运行结果
安装Groovy参考如下:
http://www.groovy-lang.org/download.html
