Logstash Java filter plugin example "./gradlew gem" error

I was following Elasticsearch document (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


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.


You need to change line 102 from

dependsOn [downloadAndInstallJRuby, removeObsoleteJars, vendor, generateRubySupportFiles]


dependsOn([downloadAndInstallJRuby, removeObsoleteJars, vendor, generateRubySupportFiles])


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?


I faced the same issue. I found this file (link provided below) and used in my path.


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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