转载自 http://www.paincker.com/gradle-dependencies
之前仔细研究过gradle，看的也挺全面，但是没有做过任何记录，现在发现基本上全都忘光了，所以今天看到这篇文章，赶紧记录一下。
Gradle是一个非常好用的编译工具，特别是继承了maven的依赖项管理功能，需要的Library不需要像传统IDE一样手动下载复制到项目中，只需要简单的写一行gradle脚本，就能自动下载下来并编译。
但是有时候会出现各种不明情况的报错，最常见的一种原因就是依赖项版本冲突。
每个模块都可能依赖其他模块，这些模块又会依赖别的模块。而一个项目中的多个模块，对同一个模块的不同版本有依赖，就可能产生冲突。
通过gradle命令查看依赖树，可以比较直观的看到冲突。具体方法是在模块所在的目录，也即build.gradle所在目录下执行gradle dependencies（需要将gradle加入PATH环境变量），执行结果如图。
Transitive
Transitive用于自动处理子依赖项。默认为true，gradle自动添加子依赖项，形成一个多层树形结构；设置为false，则需要手动添加每个依赖项。
案例
以安卓单元测试espresso的配置为例，gradle依赖如下：
dependencies{
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
运行gradle dependencies的结果如下。可以看到每个包的依赖项都被递归分析并添加进来。
+---com.android.support.test:runner:0.2
|+---junit:junit-dep:4.10
||\---org.hamcrest:hamcrest-core:1.1
|+---com.android.support.test:exposed-instrumentation-api-publish:0.2
|\---com.android.support:support-annotations:22.0.0
+---com.android.support.test:rules:0.2
|\---com.android.support.test:runner:0.2(*)
\---com.android.support.test.espresso:espresso-core:2.1
+---com.android.support.test:rules:0.2(*)
+---com.squareup:javawriter:2.1.1
+---org.hamcrest:hamcrest-integration:1.1
|\---org.hamcrest:hamcrest-core:1.1
+---com.android.support.test.espresso:espresso-idling-resource:2.1
+---org.hamcrest:hamcrest-library:1.1
|\---org.hamcrest:hamcrest-core:1.1
+---javax.inject:javax.inject:1
+---com.google.code.findbugs:jsr305:2.0.1
+---com.android.support.test:runner:0.2(*)
+---javax.annotation:javax.annotation-api:1.2
\---org.hamcrest:hamcrest-core:1.1
统一指定transitive
可以给dependencies统一指定transitive为false，再次执行dependencies可以看到如下结果。
configurations.all{
transitive=false
}
dependencies{
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
+---com.android.support.test:runner:0.2
+---com.android.support.test:rules:0.2
\---com.android.support.test.espresso:espresso-core:2.1
单独指定依赖项的transitive
dependencies{
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1'){
transitive=false
}
}
版本冲突
在同一个配置下（例如androidTestCompile），某个模块的不同版本同时被依赖时，默认使用最新版，gradle同步时不会报错。例如下面的hamcrest-core和runner。
dependencies{
androidTestCompile('com.android.support.test:runner:0.4')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
+---com.android.support.test:runner:0.4
|+---com.android.support:support-annotations:23.0.1
|+---junit:junit:4.12
||\---org.hamcrest:hamcrest-core:1.3
|\---com.android.support.test:exposed-instrumentation-api-publish:0.4
+---com.android.support.test:rules:0.2
|\---com.android.support.test:runner:0.2->0.4(*)
\---com.android.support.test.espresso:espresso-core:2.1
+---com.android.support.test:rules:0.2(*)
+---com.squareup:javawriter:2.1.1
+---org.hamcrest:hamcrest-integration:1.1
|\---org.hamcrest:hamcrest-core:1.1->1.3
+---com.android.support.test.espresso:espresso-idling-resource:2.1
+---org.hamcrest:hamcrest-library:1.1
|\---org.hamcrest:hamcrest-core:1.1->1.3
+---javax.inject:javax.inject:1
+---com.google.code.findbugs:jsr305:2.0.1
+---com.android.support.test:runner:0.2->0.4(*)
+---javax.annotation:javax.annotation-api:1.2
\---org.hamcrest:hamcrest-core:1.1->1.3
Force
force强制设置某个模块的版本。
configurations.all{
resolutionStrategy{
force'org.hamcrest:hamcrest-core:1.3'
}
}
dependencies{
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
可以看到，原本对hamcrest-core 1.1的依赖，全部变成了1.3。
+---com.android.support.test:runner:0.2
|+---junit:junit-dep:4.10
||\---org.hamcrest:hamcrest-core:1.1->1.3
|+---com.android.support.test:exposed-instrumentation-api-publish:0.2
|\---com.android.support:support-annotations:22.0.0
+---com.android.support.test:rules:0.2
|\---com.android.support.test:runner:0.2(*)
\---com.android.support.test.espresso:espresso-core:2.1
+---com.android.support.test:rules:0.2(*)
+---com.squareup:javawriter:2.1.1
+---org.hamcrest:hamcrest-integration:1.1
|\---org.hamcrest:hamcrest-core:1.1->1.3
+---com.android.support.test.espresso:espresso-idling-resource:2.1
+---org.hamcrest:hamcrest-library:1.1
|\---org.hamcrest:hamcrest-core:1.1->1.3
+---javax.inject:javax.inject:1
+---com.google.code.findbugs:jsr305:2.0.1
+---com.android.support.test:runner:0.2(*)
+---javax.annotation:javax.annotation-api:1.2
\---org.hamcrest:hamcrest-core:1.1->1.3
Exclude
Exclude可以设置不编译指定的模块
configurations{
all*.excludegroup:'org.hamcrest',module:'hamcrest-core'
}
dependencies{
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
+---com.android.support.test:runner:0.2
|+---junit:junit-dep:4.10
|+---com.android.support.test:exposed-instrumentation-api-publish:0.2
|\---com.android.support:support-annotations:22.0.0
+---com.android.support.test:rules:0.2
|\---com.android.support.test:runner:0.2(*)
\---com.android.support.test.espresso:espresso-core:2.1
+---com.android.support.test:rules:0.2(*)
+---com.squareup:javawriter:2.1.1
+---org.hamcrest:hamcrest-integration:1.1
+---com.android.support.test.espresso:espresso-idling-resource:2.1
+---org.hamcrest:hamcrest-library:1.1
+---javax.inject:javax.inject:1
+---com.google.code.findbugs:jsr305:2.0.1
+---com.android.support.test:runner:0.2(*)
\---javax.annotation:javax.annotation-api:1.2
单独使用group或module参数
exclude后的参数有group和module，可以分别单独使用，会排除所有匹配项。例如下面的脚本匹配了所有的group为’com.android.support.test’的模块。
configurations{
all*.excludegroup:'com.android.support.test'
}
dependencies{
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
\---com.android.support.test.espresso:espresso-core:2.1
+---com.squareup:javawriter:2.1.1
+---org.hamcrest:hamcrest-integration:1.1
|\---org.hamcrest:hamcrest-core:1.1
+---com.android.support.test.espresso:espresso-idling-resource:2.1
+---org.hamcrest:hamcrest-library:1.1
|\---org.hamcrest:hamcrest-core:1.1
+---javax.inject:javax.inject:1
+---com.google.code.findbugs:jsr305:2.0.1
+---javax.annotation:javax.annotation-api:1.2
\---org.hamcrest:hamcrest-core:1.1
单独给某个模块指定exclude
dependencies{
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1'){
excludegroup:'org.hamcrest'
}
}
+---com.android.support.test:runner:0.2
|+---junit:junit-dep:4.10
||\---org.hamcrest:hamcrest-core:1.1
|+---com.android.support.test:exposed-instrumentation-api-publish:0.2
|\---com.android.support:support-annotations:22.0.0
+---com.android.support.test:rules:0.2
|\---com.android.support.test:runner:0.2(*)
\---com.android.support.test.espresso:espresso-core:2.1
+---com.android.support.test:rules:0.2(*)
+---com.squareup:javawriter:2.1.1
+---com.android.support.test.espresso:espresso-idling-resource:2.1
+---javax.inject:javax.inject:1
+---com.google.code.findbugs:jsr305:2.0.1
+---com.android.support.test:runner:0.2(*)
\---javax.annotation:javax.annotation-api:1.2
不同配置下的版本冲突
同样的配置下的版本冲突，会自动使用最新版；而不同配置下的版本冲突，gradle同步时会直接报错。可使用exclude、force解决冲突。
例如compile 'com.android.support:appcompat-v7:23.1.1'，和androidTestCompile 'com.android.support.test.espresso:espresso-core:2.1'，所依赖的com.android.support:support-annotations版本不同，就会导致冲突。
dependencies{
compile'com.android.support:appcompat-v7:23.1.1'
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
gradle同步时会提示
Warning:Conflictwithdependency'com.android.support:support-annotations'.Resolvedversionsforappandtest app differ.
执行dependencies会提示
FAILURE:Buildfailedwithan exception.
*Whatwent wrong:
A problem occurred configuring project':app'.
>Conflictwithdependency'com.android.support:support-annotations'.Resolvedversionsforappandtest app differ.
*Try:
Runwith--stacktrace option togetthe stack trace.Runwith--infoor--debug option togetmore log output.
BUILD FAILED
不兼容
虽然可以通过force、exclude等方式避免依赖项版本冲突，使得grade同步成功，但是并不能代表编译时没有问题。由于不同版本可能不完全兼容，于是会出现各种奇怪的报错。已知的解决思路是更改包的版本、尝试强制使用不同版本的依赖项，找到可兼容的依赖组合。
报错例如：
com.android.dex.DexException:Multipledex files defineLorg/hamcrest/MatcherAssert;
at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:596)
at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:554)
at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:535)
at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:171)
at com.android.dx.merge.DexMerger.merge(DexMerger.java:189)
at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:454)
at com.android.dx.command.dexer.Main.runMonoDex(Main.java:303)
at com.android.dx.command.dexer.Main.run(Main.java:246)
at com.android.dx.command.dexer.Main.main(Main.java:215)
at com.android.dx.command.Main.main(Main.java:106)
Error:Executionfailedfortask':app:dexDebugAndroidTest'.
>com.android.ide.common.process.ProcessException:org.gradle.process.internal.ExecException:Process'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_40.jdk/Contents/Home/bin/java''finishedwithnon-zeroexitvalue2
BUILD FAILED
又例如Android执行Espresso单元测试时出现：
Runningtests
Testrunning started
java.lang.NoSuchMethodError:org.hamcrest.core.AnyOf.anyOf
at org.hamcrest.Matchers.anyOf(Matchers.java:87)
at android.support.test.espresso.Espresso.(Espresso.java:158)
at com.jzj1993.unittest.test.MainActivityEspressoTest.sayHello(MainActivityEspressoTest.java:28)
at java.lang.reflect.Method.invokeNative(NativeMethod)
at java.lang.reflect.Method.invoke(Method.java:525)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at android.support.test.internal.statement.UiThreadStatement.evaluate(UiThreadStatement.java:55)
at android.support.test.rule.ActivityTestRule$ActivityStatement.evaluate(ActivityTestRule.java:257)
at org.junit.rules.RunRules.evaluate(RunRules.java:18)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.junit.runners.Suite.runChild(Suite.java:128)
at org.junit.runners.Suite.runChild(Suite.java:24)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
at org.junit.runner.JUnitCore.run(JUnitCore.java:136)
at android.support.test.internal.runner.TestExecutor.execute(TestExecutor.java:54)
at android.support.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:228)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)
Finish
