sbt assembly遇到的两个问题

1.  deduplicate file appears in two different jar:

If multiple files share the same relative path (e.g. a resource named application.conf in multiple dependency JARs), the default strategy is to verify that all candidates have the same contents and error out otherwise.

The you need use the merge strategy.

reference: https://github.com/sbt/sbt-assembly

This behavior can be configured on a per-path basis using either one of the following built-in strategies or writing a custom one:

• MergeStrategy.deduplicate is the default described above
• MergeStrategy.first picks the first of the matching files in classpath order
• MergeStrategy.last picks the last one
• MergeStrategy.singleOrError bails out with an error message on conflict
• MergeStrategy.concat simply concatenates all matching files and includes the result
• MergeStrategy.filterDistinctLines also concatenates, but leaves out duplicates along the way
• MergeStrategy.rename renames the files originating from jar files
• MergeStrategy.discard simply discards matching files

The mapping of path names to merge strategies is done via the setting assemblyMergeStrategy which can be augmented as follows:

assemblyMergeStrategy in assembly := {  case PathList("javax", "servlet", xs @ _*)         => MergeStrategy.first  case PathList(ps @ _*) if ps.last endsWith ".html" => MergeStrategy.first  case "application.conf"                            => MergeStrategy.concat  case "unwanted.txt"                                => MergeStrategy.discard  case x =>    val oldStrategy = (assemblyMergeStrategy in assembly).value    oldStrategy(x)}

NOTE:

• assemblyMergeStrategy in assembly expects a function. You can't do assemblyMergeStrategy in assembly := MergeStrategy.first!
• Some files must be discarded or renamed otherwise to avoid breaking the zip (due to duplicate file name) or the legal license. Delegate default handling to (assemblyMergeStrategy in assembly) as the above pattern matching example.

By the way, the first case pattern in the above using PathList(...) is how you can pick javax/servlet/* from the first jar. If the default MergeStrategy.deduplicate is not working for you, that likely means you have multiple versions of some library pulled by your dependency graph. The real solution is to fix that dependency graph. You can work around it by MergeStrategy.first but don't be surprised when you see ClassNotFoundException.

Here is the default:

  val defaultMergeStrategy: String => MergeStrategy = {     case x if Assembly.isConfigFile(x) =>      MergeStrategy.concat    case PathList(ps @ _*) if Assembly.isReadme(ps.last) || Assembly.isLicenseFile(ps.last) =>      MergeStrategy.rename    case PathList("META-INF", xs @ _*) =>      (xs map {_.toLowerCase}) match {        case ("manifest.mf" :: Nil) | ("index.list" :: Nil) | ("dependencies" :: Nil) =>          MergeStrategy.discard        case ps @ (x :: xs) if ps.last.endsWith(".sf") || ps.last.endsWith(".dsa") =>          MergeStrategy.discard        case "plexus" :: xs =>          MergeStrategy.discard        case "services" :: xs =>          MergeStrategy.filterDistinctLines        case ("spring.schemas" :: Nil) | ("spring.handlers" :: Nil) =>          MergeStrategy.filterDistinctLines        case _ => MergeStrategy.deduplicate      }    case _ => MergeStrategy.deduplicate  }

Custom MergeStrategys can find out where a particular file comes from using the sourceOfFileForMerge method on sbtassembly.AssemblyUtils, which takes the temporary directory and one of the files passed into the strategy as parameters.

Third Party Merge Strategy Plugins

Support for special-case merge strategies beyond the generic scope can be provided by companion plugins, below is a non-exhaustive list:

• Log4j2 Plugin Caches (Log4j2Plugins.dat): https://github.com/idio/sbt-assembly-log4j2

2.  使用IDEA  SBT console， run command: assembly, then error occurs: Java OutOfMemory 

需要增大JVM可用内存：

调大 IDEA settings 中sbt -> VM parameters -> -Xmx1024M

调大 SBT_HOME/conf/sbtconfig.txt 中 -Xmx1024M

reference: http://blog.csdn.net/pengych_321/article/details/52004860