while filtering resources the token replacement stops at the character @

Create a simple file hello.txt under src/main/resources with following content:
"
This property ${testProperty} was replaced
but the one behind a @ will not be processed, as you
see: ${testProperty}. You shouldn't see a property reference.
"
define a build section in your pom.xml like this
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
<includes>
<include>*/.txt</include>
</includes>
</resource>
<resource>
<directory>src/main/resources</directory>
<filtering>false</filtering>
<excludes>
<exclude>*/.txt</exclude>
</excludes>
</resource>
</resources>

Run the command:

mvn process-resources -DtestProperty=IwasReplaced

this produces the output

"
This property IwasReplaced was replaced
but the one behind a @ will not be processed, as you
see: ${testProperty}. You shouldn't see a property reference.
"

As you see, the second property reference was not resolved. The replacement just stops after the @ character.