Class FileData

  • public abstract class FileData
    extends java.lang.Object
    Integration between the LaunchDarkly SDK and file data.

    The file data source allows you to use local files as a source of feature flag state. This would typically be used in a test environment, to operate using a predetermined feature flag state without an actual LaunchDarkly connection. See dataSource() for details.

    This is different from TestData, which allows you to simulate flag configurations programmatically rather than using a file.

    See Also:
    • Method Detail

      • dataSource

        public static FileDataSourceBuilder dataSource()
        Creates a FileDataSourceBuilder which you can use to configure the file data source. This allows you to use local files (or classpath resources containing file data) as a source of feature flag state, instead of using an actual LaunchDarkly connection.

        This object can be modified with FileDataSourceBuilder methods for any desired custom settings, before including it in the SDK configuration with LDConfig.Builder.dataSource(com.launchdarkly.sdk.server.subsystems.ComponentConfigurer).

        At a minimum, you will want to call FileDataSourceBuilder.filePaths(String...) to specify your data file(s); you can also use FileDataSourceBuilder.autoUpdate(boolean) to specify that flags should be reloaded when a file is modified. See FileDataSourceBuilder for all configuration options.

             FileDataSourceFactory f = FileData.dataSource()
             LDConfig config = new LDConfig.Builder()

        This will cause the client not to connect to LaunchDarkly to get feature flags. The client may still make network connections to send analytics events, unless you have disabled this with Components.noEvents(). IMPORTANT: Do not set LDConfig.Builder.offline(boolean) to true; doing so would not just put the SDK "offline" with regard to LaunchDarkly, but will completely turn off all flag data sources to the SDK including the file data source.

        Flag data files can be either JSON or YAML. They contain an object with three possible properties:

        • flags: Feature flag definitions.
        • flagVersions: Simplified feature flags that contain only a value.
        • segments: User segment definitions.

        The format of the data in flags and segments is defined by the LaunchDarkly application and is subject to change. Rather than trying to construct these objects yourself, it is simpler to request existing flags directly from the LaunchDarkly server in JSON format, and use this output as the starting point for your file. In Linux you would do this:

             curl -H "Authorization: {your sdk key}"

        The output will look something like this (but with many more properties):

             "flags": {
                 "flag-key-1": {
                     "key": "flag-key-1",
                     "on": true,
                     "variations": [ "a", "b" ]
                 "flag-key-2": {
                     "key": "flag-key-2",
                     "on": true,
                     "variations": [ "c", "d" ]
             "segments": {
                 "segment-key-1": {
                     "key": "segment-key-1",
                     "includes": [ "user-key-1" ]

        Data in this format allows the SDK to exactly duplicate all the kinds of flag behavior supported by LaunchDarkly. However, in many cases you will not need this complexity, but will just want to set specific flag keys to specific values. For that, you can use a much simpler format:

             "flagValues": {
                 "my-string-flag-key": "value-1",
                 "my-boolean-flag-key": true,
                 "my-integer-flag-key": 3

        Or, in YAML:

           my-string-flag-key: "value-1"
           my-boolean-flag-key: true
           my-integer-flag-key: 3

        It is also possible to specify both flags and flagValues, if you want some flags to have simple values and others to have complex behavior. However, it is an error to use the same flag key or segment key more than once, either in a single file or across multiple files.

        If the data source encounters any error in any file-- malformed content, a missing file, or a duplicate key-- it will not load flags from any of the files.

        a data source configuration object