Sbt 合并策略的行为不符合预期

在build.scala中，我有以下内容：

mergeStrategy <<= (mergeStrategy in assembly) {(old) => {
  case PathList("javax", "servlet",  "resources", xs @ _*) => MergeStrategy.first
  case x => old(x)
}}

表明它正在使用“重复数据消除”策略，而不是“第一”策略。这会产生以下错误：

[error] {file:/home/dan/tesla/}tesla-appengine/*:assembly: deduplicate: different file contents found in the following:
[error] /home/dan/.ivy2/cache/com.google.appengine/appengine-tools-sdk/jars/appengine-tools-sdk-1.7.3.jar:javax/servlet/resources/web-app_2_2.dtd
[error] /home/dan/.ivy2/cache/javax.servlet/servlet-api/jars/servlet-api-2.5.jar:javax/servlet/resources/web-app_2_2.dtd

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我没有在适当的范围内应用此设置。我需要设置

mergeStrategy in assembly <<= ...

在程序集中合并策略
mergeStrategy in assembly <<= ...