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I run my ProGuard for my Android project and get the following warnings: 

Note: duplicate definition of library class [org.apache.http.conn.scheme.HostNameResolver]
Note: duplicate definition of library class [org.apache.http.conn.scheme.SocketFactory]
Note: duplicate definition of library class [org.apache.http.conn.ConnectTimeoutException]
Note: duplicate definition of library class [org.apache.http.params.HttpParams]
Note: duplicate definition of library class [android.net.http.SslCertificate$DName]
Note: duplicate definition of library class [android.net.http.SslError]
Note: duplicate definition of library class [android.net.http.SslCertificate]

Note: there were 7 duplicate class definitions.

I found here to fix this with ignoring it with: 

-keep class org.apache.http.** { *; }
-dontwarn org.apache.http.**
-keep class android.net.http.** { *; }
-dontwarn android.net.http.**

I do not see a way to remove the duplicates from the used libraries. Even after using dontwarn the warnings do not vanish.

Is this the right way of handling this warning in just ignoring it or could this lead to problems?

Community
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Michael
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4 Answers4

98

If you add a proguard option -printconfiguration config.txt you'll see proguard adds

-libraryjars 'D:\tools\android\platforms\android-23\android.jar'

-libraryjars 'D:\tools\android\platforms\android-23\optional\org.apache.http.legacy.jar'

your duplicated classes (e.g. SslError) are presented in both android.jar and org.apache.http.legacy.jar

Proguard adds second jar even if you don't useLibrary 'org.apache.http.legacy' Here is an open bug describing the problem.

So now we can't do anything with the issue. Just ignore it:

-dontnote android.net.http.*
-dontnote org.apache.commons.codec.**
-dontnote org.apache.http.**

There is no need to keep the classes as long as they are located in library jar (phone's library actually). dontwarn doesn't work because it's not a warning, it's a note.

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Flavio
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    Great! Thanks. This answers should be marked as the correct one! – Radim Vaculik Mar 24 '16 at 13:29
  • Just tried to place `useLibrary 'org.apache.http.legacy'` in *build.gradle* and place your `-dontnote` into the proguard file. But still getting problems. I was using api 22, was working fine. Now I upgrade into 23, I'm getting these errors when trying to build the signed. Some times grade works for indefinite. Don't know what else to do. – wviana Jun 17 '16 at 22:09
  • Where I add this option `proguard option -printconfiguration config.txt` ? – MML Apr 04 '19 at 22:06
  • In command line were you run proguard. The config.txt will be created at the current folder – Flavio Apr 05 '19 at 22:34
6

Probably, you have mentioned "-injars" and -libraryjars" in your proguard-project.txt,considering the latest build system takes care of mentioning them for you ..so you dont need to mention it again.

source: http://proguard.sourceforge.net/manual/troubleshooting.html#duplicateclass

I think this will help.:)

Sankalp Pandya
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    Well, I'm on a pretty new Android Studio (Dec 1, 2015 build) and nobody takes care of mentioning them for me. Am I missing something simple? – aasu Mar 09 '16 at 13:51
1

You can tell gradle not to allow duplicate classes (take only the first) by adding the following to your build.gradle:

jar {
    duplicatesStrategy = DuplicatesStrategy.EXCLUDE
}
voxoid
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    Which build.gradle? project or app? if app, under which block do you place it? i have tried to put it in my app's build.gradle android block `android{jar { duplicatesStrategy = DuplicatesStrategy.EXCLUDE } }` but i get the error **Error:Gradle DSL method not found: 'jar()'** – Edijae Crusar Jan 26 '17 at 11:20
  • `jar {` is a task within the gradle java plugin, so if you `apply plugin: 'java'` then you should be able to use that jar block; it doesn't go inside another block; it's at the root level of the build.gradle. ([see this gradle doc](https://docs.gradle.org/current/userguide/java_plugin.html#sec:jar)) I used it in an app, but not sure if that matters. – voxoid Jan 30 '17 at 14:18
-9

You can try this in your build.gradle for everything that is indicated as duplicate in the logs. I am not sure if this will work, so try it out and inform if it works or not.

packagingOptions {
        exclude 'android.net.http.SslCertificate'
    }
Amit Tiwari
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