Tutorial: Retrieving Information About the Current Document by Invoking Java Operations from JavaScript Code

Suppose that you want to retrieve the names of the allowed elements that a user can insert at the current cursor position.

First, you have to implement a Java class to extend the ro.sync.ecss.extensions.api.webapp.AuthorOperationWithResult class which will be invoked to return a result to the JavaScript code.

package com.example.plugin;

import java.util.ArrayList;
import java.util.List;

import javax.swing.text.BadLocationException;

import org.apache.log4j.Logger;

import ro.sync.contentcompletion.xml.CIElement;
import ro.sync.contentcompletion.xml.WhatElementsCanGoHereContext;
import ro.sync.ecss.extensions.api.ArgumentsMap;
import ro.sync.ecss.extensions.api.AuthorAccess;
import ro.sync.ecss.extensions.api.AuthorOperationException;
import ro.sync.ecss.extensions.api.AuthorSchemaManager;
import ro.sync.ecss.extensions.api.webapp.AuthorDocumentModel;
import ro.sync.ecss.extensions.api.webapp.AuthorOperationWithResult;
import ro.sync.ecss.extensions.api.webapp.WebappRestSafe;

@WebappRestSafe
public class GetElementsAtCaretOperation extends AuthorOperationWithResult {
  /**
   * Logger for logging. 
   */
  private static Logger logger = Logger.getLogger(GetElementsAtCaretOperation.class.getName());

  @Override
  public String doOperation(AuthorDocumentModel model, ArgumentsMap args) throws AuthorOperationException {
    List<String> elementNames = new ArrayList<>();
    try {
      AuthorAccess authorAccess = model.getAuthorAccess();

      AuthorSchemaManager authorSchemaManager =
          authorAccess.getDocumentController().getAuthorSchemaManager();

      int caretOffset = authorAccess.getEditorAccess().getCaretOffset();
      WhatElementsCanGoHereContext context =
          authorSchemaManager.createWhatElementsCanGoHereContext(caretOffset);

      if (context != null) {
        List<CIElement> childrenElements = authorSchemaManager.whatElementsCanGoHere(context);
        if (childrenElements != null) {
          for (int i = 0; i < childrenElements.size(); i++) {
            CIElement currentElement = childrenElements.get(i);
            elementNames.add(currentElement.getQName());
          }
        }
      }
    } catch (BadLocationException e) {
      logger.error(e, e);
      throw new AuthorOperationException("An exception occured when trying to determine "
          + "the elements that can be inserted at caret offset: " + e.getMessage());
    }

    return String.join(",", elementNames);
  }
}

To invoke the Author Operation asynchronously from the JavaScript code, you have to call sync.api.ActionsManager#invokeOperation. The following code will iterate the list of all element names that can be inserted at the cursor position:

var actionsManager = editor.getActionsManager();
actionsManager.invokeOperation('com.example.plugin.GetElementsAtCaretOperation', {}, 
    function(e, result) {
        result.split(',').forEach(function (elementName) {
            // ......
        });
    });