# Logstash Java filter plugin example "./gradlew gem" error
**URL:** https://discuss.elastic.co/t/logstash-java-filter-plugin-example-gradlew-gem-error/257110
**Category:** Logstash
**Created:** [November 30, 2020, 6:09pm UTC](https://discuss.elastic.co/t/logstash-java-filter-plugin-example-gradlew-gem-error/257110 "2020-11-30T18:09:07Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@lakechat](https://discuss.elastic.co/u/lakechat)
#### Post date: [November 30, 2020, 6:09pm UTC](https://discuss.elastic.co/t/logstash-java-filter-plugin-example-gradlew-gem-error/257110/1 "2020-11-30T18:09:07Z")
I was following Elasticsearch document ([https://www.elastic.co/guide/en/logstash/current/java-filter-plugin.html](https://www.elastic.co/guide/en/logstash/current/java-filter-plugin.html)) to write a Java filter plugin for Logtash. Somehow, I could not even get the provided example work. I stuck at " ./gradlew gem" stage. Here is the error message:
_FAILURE: Build failed with an exception._
\*\* Where:\*
_Build file '/Users/taoli/Documents/java\_code/logstash-filter-java\_filter\_example/build.gradle' line: 102_
\*\* What went wrong:\*
_A problem occurred configuring root project 'logstash-filter-java\_filter\_example'._
_\> Could not create task ':gem'._
_\> No signature of method: org.gradle.api.internal.tasks.DefaultTaskDependency$TaskDependencySet.getAt() is applicable for argument types: (ArrayList) values: [[task ':downloadAndInstallJRuby', task ':removeObsoleteJars', ...]]_
_Possible solutions: getAt(int), getAt(java.lang.String), getAt(java.lang.String), head(), putAt(java.lang.String, java.lang.Object), wait()_
I have plugin project and Logstash project in two different folders, and added gradle.properties file in the plugin project with value
_LOGSTASH\_CORE\_PATH=/Users/taoli/Documents/java\_code/logstash\_src/logstash-core_
I suspect that in build.gradle file, something wrong with this line:
_apply from: LOGSTASH\_CORE\_PATH + "/../rubyUtils.gradle"_
Because when I tried with "./gradlew build", it complained that it could not find all Logstash api methods.
---
### Author:  [@paul.devereux](https://discuss.elastic.co/u/paul.devereux)
#### Post date: [December 1, 2020, 11:12am UTC](https://discuss.elastic.co/t/logstash-java-filter-plugin-example-gradlew-gem-error/257110/2 "2020-12-01T11:12:17Z")
Hi,
You need to change line 102 from
dependsOn [downloadAndInstallJRuby, removeObsoleteJars, vendor, generateRubySupportFiles]
to
dependsOn([downloadAndInstallJRuby, removeObsoleteJars, vendor, generateRubySupportFiles])
Regards
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### Author:  [@lakechat](https://discuss.elastic.co/u/lakechat)
#### Post date: [December 1, 2020, 6:01pm UTC](https://discuss.elastic.co/t/logstash-java-filter-plugin-example-gradlew-gem-error/257110/3 "2020-12-01T18:01:54Z")
Hi Paul,
Thanks for the response. It did let me move forward by downloading required libraries. But "compileJava" task still fails. It could not find the Logstash apis. So I guess this statement failed:
_apply from: LOGSTASH\_CORE\_PATH + "/../rubyUtils.gradle"_
Any idea what went wrong?
Thanks.
---
### Author:  [@Cnu311](https://discuss.elastic.co/u/Cnu311)
#### Post date: [December 2, 2020, 3:02pm UTC](https://discuss.elastic.co/t/logstash-java-filter-plugin-example-gradlew-gem-error/257110/4 "2020-12-02T15:02:37Z")
Hi,
I faced the same issue. I found this file (link provided below) and used in my path.
>
---
### Author:  [@lakechat](https://discuss.elastic.co/u/lakechat)
#### Post date: [December 3, 2020, 12:18am UTC](https://discuss.elastic.co/t/logstash-java-filter-plugin-example-gradlew-gem-error/257110/5 "2020-12-03T00:18:57Z")
Hi,
I am able to compile, build and install gem now. Here are what happened:
1. In plugin project, modify build.gradle line 102, add '()" as pointed out by Paul
2. In the same file, for this line
_implementation fileTree(dir: LOGSTASH\_CORE\_PATH, include: "build/libs/logstash-core-?.?.?.jar")_
it seems not working, so I just replace it with direct path, like this
_implementation files('/Users/test/workspace/logstash/logstash-core/build/libs/logstash-core-7.10.1.jar')_
1. It requires JDK to install gem. Somehow, only JDK 8.0 works for me.
Hope these help.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [December 31, 2020, 12:19am UTC](https://discuss.elastic.co/t/logstash-java-filter-plugin-example-gradlew-gem-error/257110/6 "2020-12-31T00:19:12Z")
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