META-INF

What is META-INF?

Metadata are “data that provide information about other data”. Two types of metadata exist: structural metadata and descriptive metadata. Structural metadata are data about the containers of data. Descriptive metadata use individual instances of application data or the data content.

In Java, you often see a META-INF folder containing some meta files. Have you ever asked yourself what the purpose of this folder is and what can be put in there? Well i think i could answer that roughly.

The META-INF folder is the home fort the MANIFEST.MF file. This file contains meta data about the contents of the JAR. For example, there is an entry called Main-Class that specifies the name of the Java class with the static main() for executable JAR files.

You can also place static resources in there.

In example:

META-INF/resources/button.jpg and get them in web3.0-container via http://localhost/myapp/button.jpg

Anyway, if you ever get an error of this manner;

Error:duplicate files during packaging of APK E:\Code\iDoc\app\build\outputs\apk\app-debug-unaligned.apk

Path in archive: META-INF/license.txt

Origin 1: E:\Code\iDoc\app\libs\spring-core-3.1.0.RELEASE.jar

Origin 2: E:\Code\iDoc\app\libs\spring-web-3.1.0.RELEASE.jar

You can ignore those files in your build.gradle:

android {

  packagingOptions {
  
    exclude 'META-INF/license.txt'
    
  }
  
}

probably the issue is that the packaging options for the META-INF are lacking.

Add this to your gradle file.

packagingOptions{

    exclude 'META-INF/DEPENDENCIES'
    
    exclude 'META-INF/NOTICE'
    
    exclude 'META-INF/LICENSE'
    
    exclude 'META-INF/LICENSE.txt'
    
    exclude 'META-INF/NOTICE.txt'
}

And voila! Run gradle again and there you have it. You fixed a META-INF bug.