From 0cbac88f6b4c78de887189831e862eea6bf4c296 Mon Sep 17 00:00:00 2001 From: Decebal Suiu Date: Tue, 15 Apr 2014 16:42:35 +0300 Subject: [PATCH] update readme --- README.md | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/README.md b/README.md index 485a393..58ba4b7 100644 --- a/README.md +++ b/README.md @@ -157,6 +157,44 @@ and in plugin respository you must have a plugin.properties file with the below For more information please see the demo sources. +Plugin lifecycle +-------------------------- +Each plugin passes through a pre-defined set of states. [PluginState](https://github.com/decebals/pf4j/blob/master/pf4j/src/main/java/ro/fortsoft/pf4j/PluginState.java) defines all possible states. +The primary plugin states are: +- CREATED +- DISABLED +- STARTED +- STOPPED + +The DefaultPluginManager contains the following logic: + +1. all plugins are resolved & loaded +2. *DISABLED* plugins are NOT automatically *STARTED* by pf4j in `startPlugins()` BUT you may manually start (and therefore enable) a *DISABLED* plugin by calling `startPlugin(pluginId)` instead of `enablePlugin(pluginId)` + `startPlugin(pluginId)` +3. only *STARTED* plugins may contribute extensions. Any other state should not be considered ready to contribute an extension to the running system. + +The differences between a DISABLED plugin and a STARTED plugin are: +1. a STARTED plugin has executed Plugin.start(), a DISABLED plugin has not +2. a STARTED plugin may contribute extension instances, a DISABLED plugin may not + +DISABLED plugins still have valid class loaders and their classes can be manually +loaded and explored, but the resource loading - which is important for inspection - +has been handicapped by the DISABLED check. + +As integrators of pf4j evolve their extension APIs it will become +a requirement to specify a minimum system version for loading plugins. +Loading & starting a newer plugin on an older system could result in +runtime failures due to method signature changes or other class +differences. +For this reason was added a manifest attribute (in PluginDescriptor) to specify a 'requires' version +which is a minimum system version. Also DefaultPluginManager contains a method to +specify the system version of the plugin manager and the logic to disable +plugins on load if the system version is too old (if you want total control, please override isPluginValid() method). This works for both +loadPlugins() and loadPlugin(). + +__PluginStateListener__ defines the interface for an object that listens to plugin state changes. You can use ```addPluginStateListener(PluginStateListener listener)``` and ```removePluginStateListener(PluginStateListener listener)``` from PluginManager if you want to add or remove a plugin state listener. + +Your application, as a PF4J consumer, has full control over each plugin (state). So, you can load, unload, enable, disable, start, stop and delete a certain plugin using PluginManager (programmatically). + Development mode -------------------------- PF4J can run in two modes: **DEVELOPMENT** and **DEPLOYMENT**.