I am currently at the move to write an IntelliJ plugin. I want to be able to store/restore a set of tabs to switch between different tab sessions (comparable to browser plugins like Session Manager or Session Buddy).

Therefore i need basically three types of actions:

Read open tabs (which file and editor is used?)
Store that information persistently as a tab session
Open tabs of selected session and close all others

I looked at the available actions: IdeActions.java - it seems that there is not what i am searching for. But maybe i am looking at the wrong place. Can anyone tell me if what's i am trying to achieve is possible and give me some pointers in the right direction?

Update

I succesfully created the plugin and it's available at Github: http://alp82.github.com/idea-tabsession/

It is available in the official plugin repository: Tab Session.

Update 2

Here is a follow-up question regarding splitted windows: Retrieving and setting split window settings

Update 2017

I discontinue support for this plugin because IDEA already supports that feature. You can save and load contexts easily as shown here: https://github.com/alp82/idea-tabsession#discontinued

Update

The plugin is up and ready and can be downloaded in IDEA -> Settings -> Plugins. Source code is available at: https://github.com/alp82/idea-tabsession

Short Answer

To read which tabs are open right now, use the EditorFactory and FileDocumentManager Singletons:

    Editor[] editors = EditorFactory.getInstance().getAllEditors();
    FileDocumentManager fileDocManager = FileDocumentManager.getInstance();
    for(Editor editor : editors) {
        VirtualFile vf = fileDocManager.getFile(editor.getDocument());
        String path = vf.getCanonicalPath();
        System.out.println("path = " + path);
    }

To open tabs use the FileEditorManager singleton (files being a String Array of canonical paths):

    FileEditorManager fileEditorManager = FileEditorManager.getInstance(project);
    for(String path : files) {
        System.out.println("path = " + path);
        VirtualFile vf = LocalFileSystem.getInstance().findFileByPath(path);
        fileEditorManager.openFile(vf, true, true);
    }

Long Answer

Prerequisites

Activate the Plugin Development, Groovy and UI Designer plugins
New Project -> IntelliJ IDEA Plugin

Checkout IDEA Community Edition sources to any folder:

git clone git://git.jetbrains.org/idea/community.git idea

Configure IDEA SDK and create plugin

Plugin Structure

After you have created your plugin you need to edit your plugin.xml located in the META-INF folder. Modify the id, name and description.

We need a configuration file for persistant storage. Create a mystorage.xml file in your src folder. It's now time to create the needed files:

SessionComponent.java (create it with the Add Project Component wizard to automatically create the needed xml settings):

@State(
    name = "SessionComponent",
    storages = {
        @Storage(id = "default", file = StoragePathMacros.PROJECT_FILE),
        @Storage(id = "dir", file = StoragePathMacros.PROJECT_CONFIG_DIR + "/mystorage.xml", scheme = StorageScheme.DIRECTORY_BASED)
    }
)
public class SessionComponent implements ProjectComponent, PersistentStateComponent<SessionState> {

    Project project;
    SessionState sessionState;

    public SessionComponent(Project project) {
        this.project = project;
        sessionState = new SessionState();
    }

    public void initComponent() {
        // TODO: insert component initialization logic here
    }

    @Override
    public void loadState(SessionState sessionState) {
        System.out.println("load sessionState = " + sessionState);
        this.sessionState = sessionState;
    }

    public void projectOpened() {
        // called when project is opened
    }

    public void projectClosed() {
        // called when project is being closed
    }

    @Nullable
    @Override
    public SessionState getState() {
        System.out.println("save sessionState = " + sessionState);
        return sessionState;
    }

    public void disposeComponent() {
        // TODO: insert component disposal logic here
    }

    @NotNull
    public String getComponentName() {
        return "SessionComponent";
    }

    public int saveCurrentTabs() {
        Editor[] editors = getOpenEditors();
        FileEditorManager fileEditorManager = FileEditorManager.getInstance(project);
        VirtualFile[] selectedFiles = fileEditorManager.getSelectedFiles();

        FileDocumentManager fileDocManager = FileDocumentManager.getInstance();
        sessionState.files = new String[editors.length];
        int i = 0;
        for(Editor editor : editors) {
            VirtualFile vf = fileDocManager.getFile(editor.getDocument());
            String path = vf.getCanonicalPath();
            System.out.println("path = " + path);
            if(path.equals(selectedFiles[0].getCanonicalPath())) {
                sessionState.focusedFile = path;
            }
            sessionState.files[i] = path;
            i++;
        }

        return editors.length;
    }

    public int loadSession() {
        closeCurrentTabs();
        FileEditorManager fileEditorManager = FileEditorManager.getInstance(project);
        for(String path : sessionState.files) {
            System.out.println("path = " + path);
            VirtualFile vf = LocalFileSystem.getInstance().findFileByPath(path);
            fileEditorManager.openFile(vf, true, true);
        }

        return sessionState.files.length;
    }

    public void closeCurrentTabs() {
        Editor[] editors = getOpenEditors();
        FileEditorManager fileEditorManager = FileEditorManager.getInstance(project);
        FileDocumentManager fileDocManager = FileDocumentManager.getInstance();
        for(Editor editor : editors) {
            System.out.println("editor = " + editor);
            VirtualFile vf = fileDocManager.getFile(editor.getDocument());
            fileEditorManager.closeFile(vf);
        }
    }

    public void showMessage(String htmlText) {
        StatusBar statusBar = WindowManager.getInstance().getStatusBar(project);
        JBPopupFactory.getInstance()
            .createHtmlTextBalloonBuilder(htmlText, MessageType.INFO, null)
            .setFadeoutTime(7500)
            .createBalloon()
            .show(RelativePoint.getCenterOf(statusBar.getComponent()), Balloon.Position.atRight);
    }

    private Editor[] getOpenEditors() {
        return EditorFactory.getInstance().getAllEditors();
    }

}

We also need the storage class:

public class SessionState {
    public String[] files = new String[0];
    public String focusedFile = "";

    public String toString() {
        String result = "";
        for (String file : files) {
            result += file + ", ";
        }
        result += "selected: " + focusedFile;
        return result;
    }
}

The component class should have an entry in your plugin.xml like this one:

<project-components>
  <component>
    <implementation-class>my.package.SessionComponent</implementation-class>
  </component>
</project-components>

The component class offers all needed functionality, but is never be used. Therefore, we need actions to perform loading and saving:

Save.java:

public class Save extends AnAction {

    public Save() {
        super();
    }

    public void actionPerformed(AnActionEvent event) {
        Project project = event.getData(PlatformDataKeys.PROJECT);
        SessionComponent sessionComponent = project.getComponent(SessionComponent.class);

        int tabCount = sessionComponent.saveCurrentTabs();
        String htmlText = "Saved " + String.valueOf(tabCount) + " tabs";
        sessionComponent.showMessage(htmlText);
    }

}

Load.java:

public class Load extends AnAction {

    public Load() {
        super();
    }

    public void actionPerformed(AnActionEvent event) {
        Project project = event.getData(PlatformDataKeys.PROJECT);
        SessionComponent sessionComponent = project.getComponent(SessionComponent.class);

        int tabCount = sessionComponent.loadSession();
        String htmlText = "Loaded " + String.valueOf(tabCount) + " tabs";
        sessionComponent.showMessage(htmlText);
    }

}

Aaand... Action!

Last thing we need is the user interface to select those actions. Simply put this in your plugin.xml:

  <actions>
    <!-- Add your actions here -->
      <group id="MyPlugin.SampleMenu" text="_Sample Menu" description="Sample menu">
          <add-to-group group-id="MainMenu" anchor="last"  />
          <action id="MyPlugin.Save" class="my.package.Save" text="_Save" description="A test menu item" />
          <action id="MyPlugin.Load" class="my.package.Load" text="_Load" description="A test menu item" />
      </group>
  </actions>

Plugin Deployment

The basic functionality is ready. I will add support for multiple sessions and some other neat stuff before deploying this plugin and releasing it to the open-source community. Link will be posted here, when it's online.