Finite State Machine (FSM)

Each FSM instances contains a name, a data item, and a state diagram. It may recieven events. If they events are unrecognized then either an exception gets thrown or no action gets taken. If, however, the event is recognized, then any corresponding customer handler code may get executed then the current state possibly changed. Cyclic state transition diagrams are supported through use of the Transition.toStateName field naming the cyclic static. All other transition should use the Transition.toState field.

Each State may include a data item. Each event may include a data argument. JSON Serialization/Deserialization is support for the state diagram/configuration, but not for the custom event handler code blocks.

Example 1: Test FSM

This is an example FSM build via the Java API.

$ /Library/Java/JavaVirtualMachines/jdk-17.0.1.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=63716:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /opt/workspace/personal/fsm/target/classes:/opt/workspace/personal/personal-environment-files/home-dot_m2/repository/org/apache/commons/commons-lang3/3.12.0/commons-lang3-3.12.0.jar:/opt/workspace/personal/personal-environment-files/home-dot_m2/repository/com/fasterxml/jackson/core/jackson-core/2.13.0/jackson-core-2.13.0.jar:/opt/workspace/personal/personal-environment-files/home-dot_m2/repository/com/fasterxml/jackson/core/jackson-databind/2.13.0/jackson-databind-2.13.0.jar:/opt/workspace/personal/personal-environment-files/home-dot_m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.13.0/jackson-annotations-2.13.0.jar com.tiffanytimbric.fsm.Main
FSM JSON Definition:
{"@class":"com.tiffanytimbric.fsm.FiniteStateMachine","name":"Test FSM","dataItem":"fsm_dataItem","ignoreUnknownEvents":true,"initialState":{"@class":"com.tiffanytimbric.fsm.State","name":"Morning Shift","dataItem":"state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Lunch Time","dataArg":"event_dataArg"},"toState":{"@class":"com.tiffanytimbric.fsm.State","name":"At Lunch","dataItem":"state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Afternoon Shift Start","dataArg":"event_dataArg"},"toState":{"@class":"com.tiffanytimbric.fsm.State","name":"Afternoon Shift","dataItem":"state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Postpone Shift Start","dataArg":"event_dataArg"},"toState":null,"toStateName":"At Lunch"}]},"toStateName":null}]},"toStateName":null}]}}

Test FSM, fsm_dataItem: Start
    Current State: "Morning Shift", "state_dataItem"
    Supported Events: [Lunch Time]

    Sending event: "Lunch Time"
    handleEvent("Lunch Time", "event_dataArg"): Transitioning To State "At Lunch".
    Current State: "At Lunch", "state_dataItem"
    Supported Events: [Afternoon Shift Start]

    Sending event: "Bus Arrives"
    Current State: "At Lunch", "state_dataItem"
    Supported Events: [Afternoon Shift Start]

    Sending event: "Afternoon Shift Start"
    handleEvent("Afternoon Shift Start", "event_dataArg"): Transitioning To State "Afternoon Shift".
    Current State: "Afternoon Shift", "state_dataItem"
    Supported Events: [Postpone Shift Start]

    Sending event: "Postpone Shift Start"
    handleEvent("Postpone Shift Start", "event_dataArg"): Transitioning To State "At Lunch".
    Current State: "At Lunch", "state_dataItem"
    Supported Events: [Afternoon Shift Start]

    Sending event: "Afternoon Shift Start"
    handleEvent("Afternoon Shift Start", "event_dataArg"): Transitioning To State "Afternoon Shift".
    Current State: "Afternoon Shift", "state_dataItem"
    Supported Events: [Postpone Shift Start]
Test FSM: End

FSM From-JSON JSON Definition:
{"@class":"com.tiffanytimbric.fsm.FiniteStateMachine","name":"Test FSM","dataItem":"fsm_dataItem","ignoreUnknownEvents":true,"initialState":{"@class":"com.tiffanytimbric.fsm.State","name":"Morning Shift","dataItem":"state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Lunch Time","dataArg":"event_dataArg"},"toState":{"@class":"com.tiffanytimbric.fsm.State","name":"At Lunch","dataItem":"state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Afternoon Shift Start","dataArg":"event_dataArg"},"toState":{"@class":"com.tiffanytimbric.fsm.State","name":"Afternoon Shift","dataItem":"state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Postpone Shift Start","dataArg":"event_dataArg"},"toState":null,"toStateName":"At Lunch"}]},"toStateName":null}]},"toStateName":null}]}}

Example 2: Entity View Mode FSM

This is a custom FSM read from a JSON file. It is interacted with dynamically on the command shell via the "Send Event:" command prompt.

$ /Library/Java/JavaVirtualMachines/jdk-17.0.1.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=63172:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /opt/workspace/personal/fsm/target/classes:/opt/workspace/personal/personal-environment-files/home-dot_m2/repository/org/apache/commons/commons-lang3/3.12.0/commons-lang3-3.12.0.jar:/opt/workspace/personal/personal-environment-files/home-dot_m2/repository/com/fasterxml/jackson/core/jackson-core/2.13.0/jackson-core-2.13.0.jar:/opt/workspace/personal/personal-environment-files/home-dot_m2/repository/com/fasterxml/jackson/core/jackson-databind/2.13.0/jackson-databind-2.13.0.jar:/opt/workspace/personal/personal-environment-files/home-dot_m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.13.0/jackson-annotations-2.13.0.jar com.tiffanytimbric.fsm.Main fsm-entity-view-mode.json

FSM Definition:
{"@class":"com.tiffanytimbric.fsm.FiniteStateMachine","name":"Entity View Mode FSM","dataItem":"fsm_dataItem","ignoreUnknownEvents":true,"initialState":{"@class":"com.tiffanytimbric.fsm.State","name":"Readonly","dataItem":"readonly_state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Delete","dataArg":"delete_event_dataArg"},"toState":{"@class":"com.tiffanytimbric.fsm.State","name":"Deleted","dataItem":"deleted_state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Undelete","dataArg":"undelete_event_dataArg"},"toState":null,"toStateName":"Readonly"}]},"toStateName":null},{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Edit","dataArg":"edit_event_dataArg"},"toState":{"@class":"com.tiffanytimbric.fsm.State","name":"In Edit","dataItem":"in_edit_state_dataItem","transitions":[{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Save","dataArg":"save_event_dataArg"},"toState":null,"toStateName":"Readonly"},{"@class":"com.tiffanytimbric.fsm.Transition","event":{"@class":"com.tiffanytimbric.fsm.Event","name":"Cancel","dataArg":"cancel_event_dataArg"},"toState":null,"toStateName":"Readonly"}]},"toStateName":null}]}}

    Current State: "Readonly", "readonly_state_dataItem"
    Supported Events: [Delete, Edit]
Send event: Edit

    Current State: "In Edit", "in_edit_state_dataItem"
    Supported Events: [Save, Cancel]
Send event: asdf

    Current State: "In Edit", "in_edit_state_dataItem"
    Supported Events: [Save, Cancel]
Send event: Save

    Current State: "Readonly", "readonly_state_dataItem"
    Supported Events: [Delete, Edit]
Send event: Delete

    Current State: "Deleted", "deleted_state_dataItem"
    Supported Events: [Undelete]
Send event: Undelete

    Current State: "Readonly", "readonly_state_dataItem"
    Supported Events: [Delete, Edit]