gradle学习(13)-有的没的

## 1.用脚本创建目录 通常情况下，创建目录使用mkdir来创建目录，但是有一种更好的方式来做到，避免每次都手动创建。定义一个任务来创建目录，然后用dependsOn来依赖该任务，这有可以在需要的时候创建目录。 ~~~ def classesDir = new File('build/classes') task resources << { classesDir.mkdirs() } task compile(dependsOn:'resources')<<{ if(classesDir.isDirectory()){ println 'The class directory exists.I canoperate' } } ~~~ 执行compile任务 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q compile The class directory exists.I canoperate ~~~ 然后就会在该目录下生成build/classes目录  ## 2.gradle属性和系统属性 有3种方式添加属性，命令行中的-P和-D参数，以及属性文件gradle.properties **通过命令行中的－P命令传递属性。首先build.gradle定义属性** ~~~ task printProps <<{ println commandLineProjectProp } ~~~ 在命令行中执行该命令，如果不带参数会出错。 ~~~ ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps FAILURE: Build failed with an exception. * Where: Build file '/Users/qianhui/Documents/Developer/gradle_project/0111/build.gradle' line: 2 * What went wrong: Execution failed for task ':printProps'. > Could not find property 'commandLineProjectProp' on task ':printProps'. * Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. ~~~ ~~~ gradle -q printProps -PcommandLineProjectProp=thisisacommandlineprop ~~~ 输出如下 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps -PcommandLineProjectProp=thisisacommandlineprop thisisacommandlineprop ~~~ 上面的写法一定要注意，-P后面也可以有空格，执行的效果是一样的。 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps -P commandLineProjectProp=thisisacommandlineprop thisisacommandlineprop ~~~ 但是等号（＝）两端不能有空格,且属性值也不能有空格。但是如果你用单引号 或者双引号包裹的话可以有空格。 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps -P commandLineProjectProp =this is acommandlineprop FAILURE: Build failed with an exception. * What went wrong: Task '=this' not found in root project '0111'. * Try: Run gradle tasks to get a list of available tasks. Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. ~~~ 用单引号或双引号包裹 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps -P commandLineProjectProp='this is a commandline prop' this is a commandline prop ~~~ ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q&nbsp; printProps -P commandLineProjectProp="this is a commandline prop" this is a commandline prop ~~~ **－D添加gradle属性。** build.gradle文件如下 如果这个时候我们还想刚才那样执行命令的话，会报错 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps -P commandLineProjectProp="this is a commandline prop" this is a commandline prop FAILURE: Build failed with an exception. * Where: Build file '/Users/qianhui/Documents/Developer/gradle_project/0111/build.gradle' line: 3 * What went wrong: Execution failed for task ':printProps'. > Could not find property 'systemProjectProp' on task ':printProps'. * Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. ~~~ 说明build.gradle定义的systemProjectProp不存在，这个时候就需要用-D来添加gradle属性 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps -P commandLineProjectProp="this is a commandline prop" -D org.gradle.project.systemProjectProp="this a gradle property" this is a commandline prop this a gradle property ~~~ **gradle.properties文件添加属性** build.gradle文件添加一个属性 ~~~ task printProps <<{ println commandLineProjectProp println systemProjectProp println gradleFileProperties } ~~~ 这个时候执行命令，会报错 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps -P commandLineProjectProp="this is a commandline prop" -D org.gradle.project.systemProjectProp="this a gradle property" this is a commandline prop this a gradle property FAILURE: Build failed with an exception. * Where: Build file '/Users/qianhui/Documents/Developer/gradle_project/0111/build.gradle' line: 4 * What went wrong: Execution failed for task ':printProps'. > Could not find property 'gradleFileProperties' on task ':printProps'. * Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. ~~~ 在gradle.properties 文件中添加属性 ~~~ gradleFileProperties = gradleFileProperties ~~~ 这个时候执行命令 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q printProps -P commandLineProjectProp="this is a commandline prop" -D org.gradle.project.systemProjectProp="this a gradle property" this is a commandline prop this a gradle property gradleFileProperties ~~~ ## 3.包含其他构建脚本 gradle 允许你包含其他构建的脚本，比如一些模版脚本，这样的扩展性挺好。 定义一个模版脚本:template.gradle ~~~ task hello <<{ println "this a template" } ~~~ 然后在build.gradle脚本中包含改脚本 ~~~ apply from:'template.gradle' ~~~ 执行任务hello ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q hello this a template ~~~ ## 4.自定义对象 ~~~ task configure <<{ def pos = configure(new java.text.FieldPosition(10)){ beginIndex = 1 endIndex = 5 } println pos.beginIndex println pos.endIndex } ~~~ ## 5.使用外部的脚本自定义对象 template.gradle修改如下： ~~~ beginIndex = 1 endIndex = 5 ~~~ build.gradle修改如下 ~~~ task configure <<{ def pos = new java.text.FieldPosition(10) apply from:'template.gradle',to:pos println pos.beginIndex println pos.endIndex } ~~~ 其中的apply from:'template.gradle',to :pos将template的属性注入到pos对象中。执行命令后，输出是一样的。 ~~~ qianhuis-Mac-mini:0111 qianhui$ gradle -q configure 1 5 ~~~ ## 6.缓存 gradle创建了一个.gradle目录用来缓存编译的脚本。只有变换的时候，才会重新生成缓存的脚本。