Gradle依赖项学习总结，dependencies、transitive、force、exclude的使用与依赖冲突解决

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：

1. dependencies {
2. androidTestCompile('com.android.support.test:runner:0.2')
3. androidTestCompile('com.android.support.test:rules:0.2')
4. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
5. }

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。

1. +--- com.android.support.test:runner:0.2
2. +--- junit:junit-dep:4.10
3. \--- org.hamcrest:hamcrest-core:1.1
4. +--- com.android.support.test:exposed-instrumentation-api-publish:0.2
5. \--- com.android.support:support-annotations:22.0.0
6. +--- com.android.support.test:rules:0.2
7. \--- com.android.support.test:runner:0.2 (*)
8. \--- com.android.support.test.espresso:espresso-core:2.1
9. +--- com.android.support.test:rules:0.2 (*)
10. +--- com.squareup:javawriter:2.1.1
11. +--- org.hamcrest:hamcrest-integration:1.1
12. \--- org.hamcrest:hamcrest-core:1.1
13. +--- com.android.support.test.espresso:espresso-idling-resource:2.1
14. +--- org.hamcrest:hamcrest-library:1.1
15. \--- org.hamcrest:hamcrest-core:1.1
16. +--- javax.inject:javax.inject:1
17. +--- com.google.code.findbugs:jsr305:2.0.1
18. +--- com.android.support.test:runner:0.2 (*)
19. +--- javax.annotation:javax.annotation-api:1.2
20. \--- 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。

1. configurations.all {

2. transitive = false

3. }

4. dependencies {

5. androidTestCompile('com.android.support.test:runner:0.2')

6. androidTestCompile('com.android.support.test:rules:0.2')

7. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')

8. }

9. +--- com.android.support.test:runner:0.2

10. +--- com.android.support.test:rules:0.2

11. \--- com.android.support.test.espresso:espresso-core:2.1

单独指定依赖项的transitive

1. dependencies {
2. androidTestCompile('com.android.support.test:runner:0.2')
3. androidTestCompile('com.android.support.test:rules:0.2')
4. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1') {
5. transitive = false
6. }
7. }

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。

1. dependencies {

2. androidTestCompile('com.android.support.test:runner:0.4')

3. androidTestCompile('com.android.support.test:rules:0.2')

4. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')

5. }

6. +--- com.android.support.test:runner:0.4

7. +--- com.android.support:support-annotations:23.0.1

8. +--- junit:junit:4.12

9. \--- org.hamcrest:hamcrest-core:1.3

10. \--- com.android.support.test:exposed-instrumentation-api-publish:0.4

11. +--- com.android.support.test:rules:0.2

12. \--- com.android.support.test:runner:0.2 -> 0.4 (*)

13. \--- com.android.support.test.espresso:espresso-core:2.1

14. +--- com.android.support.test:rules:0.2 (*)

15. +--- com.squareup:javawriter:2.1.1

16. +--- org.hamcrest:hamcrest-integration:1.1

17. \--- org.hamcrest:hamcrest-core:1.1 -> 1.3

18. +--- com.android.support.test.espresso:espresso-idling-resource:2.1

19. +--- org.hamcrest:hamcrest-library:1.1

20. \--- org.hamcrest:hamcrest-core:1.1 -> 1.3

21. +--- javax.inject:javax.inject:1

22. +--- com.google.code.findbugs:jsr305:2.0.1

23. +--- com.android.support.test:runner:0.2 -> 0.4 (*)

24. +--- javax.annotation:javax.annotation-api:1.2

25. \--- org.hamcrest:hamcrest-core:1.1 -> 1.3

Force

force强制设置某个模块的版本。

1. configurations.all {
2. resolutionStrategy {
3. force 'org.hamcrest:hamcrest-core:1.3'
4. }
5. }
6. dependencies {
7. androidTestCompile('com.android.support.test:runner:0.2')
8. androidTestCompile('com.android.support.test:rules:0.2')
9. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
10. }

可以看到，原本对hamcrest-core 1.1的依赖，全部变成了1.3。

1. +--- com.android.support.test:runner:0.2
2. +--- junit:junit-dep:4.10
3. \--- org.hamcrest:hamcrest-core:1.1 -> 1.3
4. +--- com.android.support.test:exposed-instrumentation-api-publish:0.2
5. \--- com.android.support:support-annotations:22.0.0
6. +--- com.android.support.test:rules:0.2
7. \--- com.android.support.test:runner:0.2 (*)
8. \--- com.android.support.test.espresso:espresso-core:2.1
9. +--- com.android.support.test:rules:0.2 (*)
10. +--- com.squareup:javawriter:2.1.1
11. +--- org.hamcrest:hamcrest-integration:1.1
12. \--- org.hamcrest:hamcrest-core:1.1 -> 1.3
13. +--- com.android.support.test.espresso:espresso-idling-resource:2.1
14. +--- org.hamcrest:hamcrest-library:1.1
15. \--- org.hamcrest:hamcrest-core:1.1 -> 1.3
16. +--- javax.inject:javax.inject:1
17. +--- com.google.code.findbugs:jsr305:2.0.1
18. +--- com.android.support.test:runner:0.2 (*)
19. +--- javax.annotation:javax.annotation-api:1.2
20. \--- org.hamcrest:hamcrest-core:1.1 -> 1.3

Exclude

Exclude可以设置不编译指定的模块

1. configurations {

2. all*.exclude group: 'org.hamcrest', module: 'hamcrest-core'

3. }

4. dependencies {

5. androidTestCompile('com.android.support.test:runner:0.2')

6. androidTestCompile('com.android.support.test:rules:0.2')

7. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')

8. }

9. +--- com.android.support.test:runner:0.2

10. +--- junit:junit-dep:4.10

11. +--- com.android.support.test:exposed-instrumentation-api-publish:0.2

12. \--- com.android.support:support-annotations:22.0.0

13. +--- com.android.support.test:rules:0.2

14. \--- com.android.support.test:runner:0.2 (*)

15. \--- com.android.support.test.espresso:espresso-core:2.1

16. +--- com.android.support.test:rules:0.2 (*)

17. +--- com.squareup:javawriter:2.1.1

18. +--- org.hamcrest:hamcrest-integration:1.1

19. +--- com.android.support.test.espresso:espresso-idling-resource:2.1

20. +--- org.hamcrest:hamcrest-library:1.1

21. +--- javax.inject:javax.inject:1

22. +--- com.google.code.findbugs:jsr305:2.0.1

23. +--- com.android.support.test:runner:0.2 (*)

24. \--- 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。

1. configurations {

2. all*.exclude group: 'com.android.support.test'

3. }

4. dependencies {

5. androidTestCompile('com.android.support.test:runner:0.2')

6. androidTestCompile('com.android.support.test:rules:0.2')

7. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')

8. }

9. \--- com.android.support.test.espresso:espresso-core:2.1

10. +--- com.squareup:javawriter:2.1.1

11. +--- org.hamcrest:hamcrest-integration:1.1

12. \--- org.hamcrest:hamcrest-core:1.1

13. +--- com.android.support.test.espresso:espresso-idling-resource:2.1

14. +--- org.hamcrest:hamcrest-library:1.1

15. \--- org.hamcrest:hamcrest-core:1.1

16. +--- javax.inject:javax.inject:1

17. +--- com.google.code.findbugs:jsr305:2.0.1

18. +--- javax.annotation:javax.annotation-api:1.2

19. \--- org.hamcrest:hamcrest-core:1.1

单独给某个模块指定exclude

1. dependencies {

2. androidTestCompile('com.android.support.test:runner:0.2')

3. androidTestCompile('com.android.support.test:rules:0.2')

4. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1') {

5. exclude group: 'org.hamcrest'

6. }

7. }

8. +--- com.android.support.test:runner:0.2

9. +--- junit:junit-dep:4.10

10. \--- org.hamcrest:hamcrest-core:1.1

11. +--- com.android.support.test:exposed-instrumentation-api-publish:0.2

12. \--- com.android.support:support-annotations:22.0.0

13. +--- com.android.support.test:rules:0.2

14. \--- com.android.support.test:runner:0.2 (*)

15. \--- com.android.support.test.espresso:espresso-core:2.1

16. +--- com.android.support.test:rules:0.2 (*)

17. +--- com.squareup:javawriter:2.1.1

18. +--- com.android.support.test.espresso:espresso-idling-resource:2.1

19. +--- javax.inject:javax.inject:1

20. +--- com.google.code.findbugs:jsr305:2.0.1

21. +--- com.android.support.test:runner:0.2 (*)

22. \--- 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。

1. dependencies {
2. compile 'com.android.support:appcompat-v7:23.1.1'
3. androidTestCompile('com.android.support.test:runner:0.2')
4. androidTestCompile('com.android.support.test:rules:0.2')
5. androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
6. }

gradle同步时会提示

1. Warning:Conflict with dependency 'com.android.support:support-annotations'. Resolved versions for app and test app differ.

执行dependencies会提示

1. FAILURE: Build failed with an exception.

2. * What went wrong:

3. A problem occurred configuring project ':app'.

4. > Conflict with dependency 'com.android.support:support-annotations'. Resolved versions for app and test app differ.

5. * Try:

6. Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

7. 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：

1. com.android.dex.DexException: Multiple dex files define Lorg/hamcrest/MatcherAssert;
2. at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:596)
3. at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:554)
4. at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:535)
5. at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:171)
6. at com.android.dx.merge.DexMerger.merge(DexMerger.java:189)
7. at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:454)
8. at com.android.dx.command.dexer.Main.runMonoDex(Main.java:303)
9. at com.android.dx.command.dexer.Main.run(Main.java:246)
10. at com.android.dx.command.dexer.Main.main(Main.java:215)
11. at com.android.dx.command.Main.main(Main.java:106)
12. Error:Execution failed for task ':app:dexDebugAndroidTest'.
13. > 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'' finished with non-zero exit value 2
14. BUILD FAILED

又例如Android执行Espresso单元测试时出现：

1. Running tests

2. Test running started

3. java.lang.NoSuchMethodError: org.hamcrest.core.AnyOf.anyOf

4. at org.hamcrest.Matchers.anyOf(Matchers.java:87)

5. at android.support.test.espresso.Espresso.<clinit>(Espresso.java:158)

6. at com.jzj1993.unittest.test.MainActivityEspressoTest.sayHello(MainActivityEspressoTest.java:28)

7. at java.lang.reflect.Method.invokeNative(Native Method)

8. at java.lang.reflect.Method.invoke(Method.java:525)

9. at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)

10. at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)

11. at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)

12. at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)

13. at android.support.test.internal.statement.UiThreadStatement.evaluate(UiThreadStatement.java:55)

14. at android.support.test.rule.ActivityTestRule$ActivityStatement.evaluate(ActivityTestRule.java:257)

15. at org.junit.rules.RunRules.evaluate(RunRules.java:18)

16. at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)

17. at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)

18. at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)

19. at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)

20. at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)

21. at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)

22. at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)

23. at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)

24. at org.junit.runners.ParentRunner.run(ParentRunner.java:300)

25. at org.junit.runners.Suite.runChild(Suite.java:128)

26. at org.junit.runners.Suite.runChild(Suite.java:24)

27. at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)

28. at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)

29. at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)

30. at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)

31. at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)

32. at org.junit.runners.ParentRunner.run(ParentRunner.java:300)

33. at org.junit.runner.JUnitCore.run(JUnitCore.java:157)

34. at org.junit.runner.JUnitCore.run(JUnitCore.java:136)

35. at android.support.test.internal.runner.TestExecutor.execute(TestExecutor.java:54)

36. at android.support.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:228)

37. at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)

38. Finish

参考资料与扩展阅读

Android Gradle配置快速入门 https://docs.gradle.org/current/userguide/dependency_management.html
http://www.concretepage.com/build-tools/gradle/gradle-exclude-transitive-dependency-example