把项目从Maven迁移到Gradle
在过去几年中，Maven已成为Java及Java EE项目事实上的构建工具，没有之一。而最近两年，Gradle获得越来越多的人使用，分走了不少Maven的用户。本文就是讲述怎样把Java EE项目从Maven迁移到Grale。
Grale是一个自动化的构建工具，类似于Ant或Maven，与这两个构建工具不同的是，Gradle引入了基于Groovy语言的DSL语法来代替XML配置，因此它的配置文件是一个Groovy文件。
安装Gradle有几种方法，最佳的方法是使用sdkman工具来安装。而要安装sdkman工具，只需简单的运行：
# curl -s get.sdkman.io | bash
Thanks for using...
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Now attempting installation...
Looking for a previous installation of SDKMAN...
Looking for unzip...
Not found.
================================================================================================
Please install unzip on your system using your favourite package manager.
Restart after installing unzip.
================================================================================================ 说明需要unzip工具，执行命令安装它：
# apt-get install unzip 再次安装sdkman
# curl -s get.sdkman.io | bash
Thanks for using...
SSSSSSSSSSSSSSS DDDDDDDDDDDDD KKKKKKKKK KKKKKKK
SS:::::::::::::::SD::::::::::::DDD K:::::::K K:::::K
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SSSSSSSSSSSSSSS DDDDDDDDDDDDD KKKKKKKKK KKKKKKK
mmmmmmm mmmmmmm aaaaaaaaaaaaa nnnn nnnnnnnn
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m::::::::::mm::::::::::m aaaaaaaaa:::::an::::::::::::::nn
m::::::::::::::::::::::m a::::ann:::::::::::::::n
m:::::mmm::::::mmm:::::m aaaaaaa:::::a n:::::nnnn:::::n
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Now attempting installation...
Looking for a previous installation of SDKMAN...
Looking for unzip...
Looking for curl...
Looking for sed...
Installing SDKMAN scripts...
Create distribution directories...
Create candidate directories...
Created for asciidoctorj: /root/.sdkman/asciidoctorj
Created for crash: /root/.sdkman/crash
Created for gaiden: /root/.sdkman/gaiden
Created for glide: /root/.sdkman/glide
Created for gradle: /root/.sdkman/gradle
Created for grails: /root/.sdkman/grails
Created for griffon: /root/.sdkman/griffon
Created for groovy: /root/.sdkman/groovy
Created for groovyserv: /root/.sdkman/groovyserv
Created for jbake: /root/.sdkman/jbake
Created for jbossforge: /root/.sdkman/jbossforge
Created for lazybones: /root/.sdkman/lazybones
Created for springboot: /root/.sdkman/springboot
Prime the config file...
Download script archive...
Extract script archive...
Install scripts...
Attempt update of bash profiles...
Updated existing /root/.profile
Updated existing /root/.bashrc
Attempt update of zsh profiles...
Created and initialised /root/.zshrc
All done!
Please open a new terminal, or run the following in the existing one:
source "/root/.sdkman/bin/sdkman-init.sh"
Then issue the following command:
sdk help
Enjoy!!! 安装完成后需要初始化sdkman：
# source "$HOME/.sdkman/bin/sdkman-init.sh" 一旦sdkman可用，那么安装Gradle就极其简单了：
# sdk install gradle
==== BROADCAST =================================================================
* 30/09/15: Gradle 2.8-rc-1 released on SDKMAN! #gradle
* 30/09/15: SDKMAN! 3.0.5 released. Fixes issue #363. http://bit.ly/1KRSKey
* 25/09/15: Grails 3.0.8 released on SDKMAN! #grailsfw
================================================================================
Downloading: gradle 2.7
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
0 0 0 354 0 0 28 0 --:--:-- 0:00:12 --:--:-- 83
100 42.7M 100 42.7M 0 0 87103 0 0:08:34 0:08:34 --:--:-- 113k
Installing: gradle 2.7
Done installing!
Do you want gradle 2.7 to be set as default? (Y/n): y
Setting gradle 2.7 as default. 下面可以开始创建构建脚本。首先要做的是创建一个名为settings.gradle的文件，设置项目名。
rootProject.name = 'my-javaee' 此文件适用于多模块的项目。
下面需要创建一个名为build.gradle的配置文件，它负责管理所有的构建过程。
apply plugin: 'war'
group = 'org.superbiz'
version = '1.0-SNAPSHOT'
description = "My JavaEE project"
sourceCompatibility = 1.8
targetCompatibility = 1.8
repositories {
mavenCentral()
}
dependencies {
providedCompile group: 'javax', name: 'javaee-api', version:'7.0'
} 注意，第一行指示构建的是一个Web项目（WAR包）。接着是项目的属性，如项目组group、版本version、描述description、Java编译器的版本、软件仓库。只有最后一行的依赖关系是必须的，它提供了构建的处理范围。
要注意，如果使用的是war插件，那么providedCompile仅有一个是有效的。如果使用的是像java这样的插件，那么需要自己实现这个函数。
可以看出，Gradle的配置文件更加精炼，没有冗余的信息。想深入Gradle就继续吧！
