[After I install jasper 7.9.0 and apply hotfix , i get error and not getting login page]

Can you post the full stack dump or log file?

[HOW TO Merge CELL IN Jasper report]

You mean, you don't want to print repeating values? Or actually want to merge cells?  Merging cells is not likely possible.

[AdHoc Cache in Jasper Reports server]

Is the REST endpoint static (url and parameters don't change)?  Are you using Jaspersoft Version 7.9.0?  If using 7.9 could be possible to use ehcache, but this would really only work if URL request is same and realize the cache is static for some period of time so subsequent calls would interact with same data since it is cached.

[Copy resources via REST API]

example written in bash to copy sample report to the "temp" directory:

copy_resp=$(curl -k -X POST "http://localhost:8080/jasperserver-pro/rest_v2/resources/temp?j_username=superuser&j_password=superuser" -H "Accept: application/json" -H "Content-Location: /public/Samples/Reports/01._Geographic_Results_by_Segment_Report")
if [[ $upload_resp == *"errorCode"* ]]; then
    echo "Copy failed"
else
   copy_uri=$(echo ${copy_resp} | jq -r '.uri')
   echo "Copied report to: "$copy_uri
fi
 

[Upload new jrxml file via REST API]

Don't mess with the descriptor.  Just upload the new JRXML file using the resources API to the files directory:

    /public/Samples/Reports/<some report uri>_files/

Or upload your JRXML files separately then reference them in your report descriptors instead of storing local.  This way you can simply replace the referenced JRXML file.

[Not able to login to jasperserver wih mysql as repo db after restart.]

Not sure on first issue, but see this for second issue: https://community.jaspersoft.com/questions/1175336/error-jasperservermaintenanceschedulerworker-2131-you-cant-specify-target-table

[is jasper report server require for JSS ?]

Studio works without the need of server and should work with latest postgres as long as you have the JDBC drivers referenced.

 

You should be able to open the JRXML files directly in studio.  Some older JRXML files may reference XML tags that are no longer valid (i.e. PDF fonts), remove those tags and it should work

 

[is jasper report server require for JSS ?]

Studio works without the need of server and should work with latest postgres as long as you have the JDBC drivers referenced.

You should be able to open the JRXML files directly in studio.  Some older JRXML files may reference XML tags that are no longer valid (i.e. PDF fonts), remove those tags and it should work.

[encrypt username and password in the Url]

This has the javascript that does the actual encryption:

<tomcat>/webapps/jasperserver-pro/scripts/runtime_dependencies/js-sdk/src/common/util/encrypter.js

[encrypt username and password in the Url]

This has the javascript that does the actual encryption:

<tomcat>/webapps/jasperserver-pro/scripts/runtime_dependencies/js-sdk/src/common/util/encrypter.js