[MASSEMBLY-916] When using mulitple Spring dependencies, the files from META-INF (from the Spring jars) overwrite each other in an executable jar-with-dependencies.

**[Brian](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=brian.stocco@genesys.com)** opened **[MASSEMBLY-916](https://issues.apache.org/jira/browse/MASSEMBLY-916?redirect=false)** and commented

When using multiple Spring jars with the assembly plugin the spring.schemas file is not correctly populated and will only include the xsd file mapping for one jar file.

This appears to be the same issue as MASSEMBLY-360, which was fixed in 2.2, but is happening again in version 3.1.1. It looks like it is only 3.1.1 that is a problem since I confirmed that the correct behaviour happens in 3.1.0.

This can go unnoticed since it is often only an issue when the xsd file urls cannot be accessed, like on an environment with no internet access. I have attached our META-INF/spring.schemas files for the same project, but built using versions 3.1.0 and 3.1.1 of the assembly plugin to illustrate the difference in output.

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**Affects:** 3.1.1

**Attachments:**
- [spring.schemas_v3.1.0.txt](https://issues.apache.org/jira/secure/attachment/12971376/spring.schemas_v3.1.0.txt) (_3.60 kB_)
- [spring.schemas_v3.1.1.txt](https://issues.apache.org/jira/secure/attachment/12971377/spring.schemas_v3.1.1.txt) (_1.14 kB_)

Compare the attached spring.schemas_v3.1.0.txt and spring.schemas_v3.1.1.txt files, then reproduce the executable jar-with-dependencies build with multiple Spring jars using assembly plugin 3.1.0 and 3.1.1. Trace the META-INF resource handling and verify that the generated spring.schemas retains mappings from every dependency without breaking the existing 3.1.0 behavior.

Written by the indexing model from the issue text.