{"id":4998,"date":"2026-08-30T02:10:35","date_gmt":"2026-08-29T17:10:35","guid":{"rendered":"https:\/\/donguri3.net\/server-tech\/resolving-kicad-freerouting-java-version-issues-2\/"},"modified":"2026-08-30T02:10:37","modified_gmt":"2026-08-29T17:10:37","slug":"resolving-kicad-freerouting-java-version-issues","status":"publish","type":"post","link":"https:\/\/donguri3.net\/en\/server-tech\/development-programming-git\/resolving-kicad-freerouting-java-version-issues\/","title":{"rendered":"KiCad Freerouting Plugin Java Version Detection Error and Countermeasures"},"content":{"rendered":"

When I launched KiCad the other day for the first time in a while, I noticed that the KiCad version had been updated to v9.0.0<\/strong>. I updated to the latest version without thinking much about it, but I ran into an issue with the Freerouting plugin, so I’m sharing it here.<\/p>\n

Installing the Freerouting Plugin<\/h2>\n
    \n
  1. Select “Plugin and Content Manager” from the KiCad home page.<\/li>\n
  2. Type “Freerouting” into the filter.<\/li>\n
  3. Click the Install button for Freerouting, click “Apply Pending Changes” at the bottom right, and complete the installation. Verify that it is registered as installed.
    \n<\/a>    \"Freerouting<\/a><\/li>\n<\/ol>\n

    Issue After Version Upgrade<\/h2>\n

    Due to the version upgrade, the Freerouting plugin<\/strong> I had been using previously was no longer installed, so I reinstalled it. However, after installing the plugin and trying to use Freerouting, the following error message started appearing.<\/p>\n

    \"Required<\/a><\/p>\n

    \n

    “Java JRE version 21 or higher is required …”<\/p>\n<\/blockquote>\n

    This error occurs when the plugin checks the Java version internally. Even though Java 21<\/strong> was actually installed correctly on my environment, the plugin incorrectly determined that the version was insufficient.
    \n    \"JRE\"<\/a><\/p>\n

    Cause of Error and Investigation<\/h2>\n

    As I investigated further, I found that the cause of the problem lies in the version check process within the Python script. Specifically, the plugin retrieves the Java version using a function like the one below.
    \nThe file is located at C:\\Users\\<USER>\\Documents\\KiCad\\9.0\\3rdparty\\plugins\\app_freerouting_kicad-plugin\\plugin.py<\/p>\n

    \n
    \n
    def get_java_version(javaPath):\n    try:\n         javaInfo = subprocess.check_output(javaPath + ' -version', shell=True, stderr=subprocess.STDOUT)\n         javaVersions = [re.search(r'([0-9\\._]+)', v).group(1).replace('\"', '') for v in javaInfo.decode().splitlines()]\n         for v in javaVersions:\n             if v.split(\".\")[0].isdigit():\n                 return v\n    except:\n         pass\n    return \"0.0.0.0\"<\/pre>\n<\/div>\n<\/div>\n
    In the code above, the java -version<\/code> command is executed using subprocess.check_output()<\/code>. However, issues around subprocess.check_output prevented it from obtaining the correct version information.<\/p>\n
    The output of java -version<\/code> looks like this, and the first line contains the accurate version information:<\/p>\n
    \n
    \n
    openjdk version \"21.0.6\" 2025-01-21 LTS\nOpenJDK Runtime Environment Temurin-21.0.6+7 (build 21.0.6+7-LTS)\nOpenJDK 64-Bit Server VM Temurin-21.0.6+7 (build 21.0.6+7-LTS, mixed mode, sharing)<\/pre>\n<\/div>\n<\/div>\n
    Solution<\/h2>\n
    I tried trial and error to figure out how to modify it so that it could retrieve the correct Java version, but in conclusion, it didn’t go well. Giving up, I implemented a temporary workaround: forcing get_java_version()<\/code> to return \"21.0.6\"<\/code> so that it would work. However, for future compatibility and support for other versions, it is preferable to fix the implementation to correctly extract the version information.<\/p>\n
    Example of Modified Code<\/h3>\n
    Below is an example of the modification reflecting the improvements mentioned above.<\/p>\n
    def get_java_version(javaPath):\n    try:\n         # May malfunction if the path contains spaces\n         javaInfo = subprocess.check_output(javaPath + ' -version', shell=True, stderr=subprocess.STDOUT)\n         javaVersions = [re.search(r'([0-9\\._]+)', v).group(1).replace('\"', '') for v in javaInfo.decode().splitlines()]\n         for v in javaVersions:\n             if v.split(\".\")[0].isdigit():\n                 return v\n    except:\n         pass\n    # Forcefully return 21.0.6\n    return \"21.0.6\"<\/pre>\n
    With this modification, \"21.0.6\"<\/code> can be accurately extracted from the output of java -version<\/code>, allowing the plugin to correctly recognize the actual version.<\/p>\n
    Conclusion<\/h2>\n
    Sometimes unexpected errors occur when upgrading KiCad or reinstalling plugins. In this case, the issue stemmed from the version retrieval process inside the Python code.
    I used a temporary workaround to forcefully return the version, but a fundamental solution has not been achieved. If anyone knows the correct way to fix this, please let me know.<\/p>\n","protected":false},"excerpt":{"rendered":"
    When I launched KiCad the other day for the first time in a while, I noticed that the KiCad version had been u […]<\/p>\n","protected":false},"author":4,"featured_media":987,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_locale":"en_US","_original_post":"https:\/\/donguri3.net\/?p=974","footnotes":""},"categories":[1172],"tags":[51,387,388,384,47,179,397],"class_list":["post-4998","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-development-programming-git","tag-git","tag-java","tag-java-21","tag-kicad","tag-python","tag-179","tag-397","en-US"],"_links":{"self":[{"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/posts\/4998","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/comments?post=4998"}],"version-history":[{"count":1,"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/posts\/4998\/revisions"}],"predecessor-version":[{"id":5001,"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/posts\/4998\/revisions\/5001"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/media\/987"}],"wp:attachment":[{"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/media?parent=4998"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/categories?post=4998"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/donguri3.net\/wp-json\/wp\/v2\/tags?post=4998"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}