Groovy学习笔记

Groovy控制台

• Groovy编译：groovyc filename.groovy
• Groovy运行：groovy filename
• Groovy控制台：groovyConsole

     

  默认导入

• groovy.lang.*
• groovy.util.*
• java.lang.*
• java.io.*
• java.math.BigDecimal.*
• java.math.BigInteger.*
• java.net.*
• java.util.*

     

  动态类型

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x = new Date(); x = 1;        //动态类型     double y = -3.1415926; y = new Date();        //静态类型，出现错误

列表与映射

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jvmLanguages = ["java","Groovy","Scala","Clojure"]; println(jvmLanguages[0]); println(jvmLanguages.size()); println(jvmLanguages[0..2]); println(jvmLanguages[-1]); jvmLanguages = []; println(jvmLanguages);     languagesRatings = [Java:100, Groovy:99, Clojure:"N/A"]; println(languagesRatings["java"]); println(languagesRatings.Clojure); languagesRatings["Clojure"] = 75; languagesRatings = [:]; println languagesRatings;

可选的语法

• 可选的分号和返回语句

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public class Test{     public Integer doStuff(){         def x = 1           //没有分号         def y; def String z = "Hello";         x = 3               //默认返回     } }

• 可选的参数括号

1 2	println("It's Groovy baby, year!") //等同于 println "It's Groovy baby, year!"

访问限定符与比较操作

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class Test{                       //默认为public             Integer x = new Integer(2)     Integer y = new Integer(2)     Integer z = null         Integer doStuff(){            //默认为public         if (x == y){              //隐含equals()调用             println "x==y"         }         if (!x.is(y)){            //检查对象是否相等             println "x is not y"         }         if (z.is(null)){          //检查是否为null             println "z is null"         }         if (z == null){           //检查是否为null             println "z is null"         }     } }

GroovyBean

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class Character{     private int strength     private int wisdom } def pc = new Character(strength:10, wisdom:15)   //bean初始化 pc.strength = 15                                 //set方法

安全解引用操作符

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people = [null, new Person(name:"liyongjie")] for (Person person : people){     println people?.name }

猫王操作符

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// Java String agentStatus = "Active"; String status = agentStatus != null ? agentStatus : "Inactive"; // Groovy String status = agentStatus ? agentStatus : "Inactive" // or String status = agentStatus ? "Inactive"

增强型字符串GString和跨行字符串

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//GString，不能用于映射中的键或者比较是否相等 String name = "liyongjie" def dist = 3 * 2 String crawling = "${name} is crawling ${dist} feet!" //跨行字符串 """This GString wraps over two lines"""

函数字面值

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def sayHello = {     name ->     if (name == "Martijn" || name == "Ben")         "Hello author" + name + "!"     else         "Hello reader" + name + "!" } println(sayHello("Martijn"))

内置的集合操作

方法	描述
each	遍历集合，对其中的每一项应用函数字面值
collect	收集在集合中每一项上应用函数字面值的返回结果（相当于其他语言map/reduce中的map函数）
inject	用函数字面值处理集合并构建返回值（相当于其他语言里map/reduce中的reduce函数）
findAll	找到集合中所有与函数字面值匹配的元素
max	返回集合中的最大值
min	返回集合中的最小值

   

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movieTitles = ["seven","show","hard"] movieTitles.each({x -> println x}) // 使用隐含的it变量 movieTitles.each({println it})

对正则表达式的内置支持

方法	描述及Java中的对等物
~	创建一个模式（创建一个编译的Java Pattern对象）
=~	创建一个匹配器（创建一个Java Matcher对象）
==~	计算字符串（相当于在Pattern上调用match()方法）

   

1 2 3 4 5 6 7	Pattern pattern = Pattern.compile("1010"); String input = "1010"; Matcher matcher = pattern.matcher(input); if (input.matches("1010")){     input = matcher.replaceFirst("0101");     System.out.println(input); }
1 2 3 4 5 6 7 8 9 10	def pattern = /1010/ def input = "1010" def matcher = input =~ pattern if (input ==~ pattern){     input = matcher.replaceFirst("0101")     println input }     ( "Hazel 1" =~ /(\w+)(\d+)/ ).each {full, name, age                                     -> println "${name} is ${age} years old."}

简单的XML处理

构造XML

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def writer = new StringWriter() def xml = new groovy.xml.MarkupBuilder(writer) xml.person(id:2) {     name "Gweneth"     age 1 } println.writer.toString()

输出的XML为：

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<person id='2'>     <name>Gweneth</name>     <age>1</age> </person>

集中解析XML的方法

方法	描述
XMLParser	支持XML文档的GPath表达式
XMLSlurper	跟XMLParser类似，但以懒加载的方式工作
DOMCategory	用一些语法支持DOM的底层解析

解析XML

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class XmlExample {     static def PERSON =     """     <person id='2'>         <name>Gweneth</name>         <age>1</age>     </person>     """ } class Person {def id; def name; def age}     def xmlPerson = new XMLParser().                     parseText(XmlExample.PERSON) Person p = new Person(id:xmlPerson.@id,                     name:xmlPerson.name.text(),                     age:xmlPerson.age.text()) println "${p.id}, ${p.name}, ${p.age}"

Groovy与Java的合作

tip:只需要把GROOVY_HOME/embeddable/Groovy-all-xxx.jar文件放到CLASSPATH中

下面是几种从Java调用Groovy代码的方法

• 使用Bean Scripting Framework(BSF)，即JSR 233
• 使用GroovyShell
• 使用GroovyClassLoader
• 使用GroovyScriptEngine
• 使用嵌入式Groovy控制台

  GroovyShell

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Binding binding = new Binding(); binding.setVariable("x", 2.4); binding.setVariable("y", 8); GroovyShell shell = new GroovyShell(binding);   //设置shell上的binding Object value = shell.evaluate("x + y");         //计算并返回表达式 assert value.equals(new BigDecimal(10.4));

GroovyClassLoader

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GroovyClassLoader loader = new GroovyClassLoader();   //准备类加载器 Class<?> groovyClass = loader.parseClass(                 new File("CalculateMax.groovy"));     //从类文件得到Class对象 GroovyObject groovyObject = (GroovyObject)                 groovyClass.newInstance();            //生成实例对象 ArrayList<Integer> numbers = new ArrayList(); numbers.add(new Integer(1));      //准备参数 numbers.add(new Integer(10)); Object[] arguments = {numbers}; Object value = GroovyObject         .invokeMethod("getMax", arguments);     //调用groovy方法 assert value.equals(new Integer(10))

GroovyScriptEngine

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String[] roots = new String[] {"/src/main/groovy"}; //设置根目录 GroovyScriptEngine gse =                 new GroovyScriptEngine(roots); //初始化引擎 Binding binding = new Binding(); binding.setVariable("name","liyongjie");     Object output = gse.run("Hello.groovy", binding); //运行脚本 assert output.equals("Hello liyongjie");