cn.dockerfoundry.ide.eclipse.server.ui.internal.actions.MenuActionHandler.java Source code

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Here is the source code for cn.dockerfoundry.ide.eclipse.server.ui.internal.actions.MenuActionHandler.java

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/*******************************************************************************
 * Copyright (c) 2012, 2014 Pivotal Software, Inc. 
 * 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Apache License, 
 * Version 2.0 (the "License); you may not use this file except in compliance 
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *  
 *  Contributors:
 *     Pivotal Software, Inc. - initial API and implementation
 ********************************************************************************/
package cn.dockerfoundry.ide.eclipse.server.ui.internal.actions;

import java.util.Collections;
import java.util.List;

import org.eclipse.core.expressions.IEvaluationContext;
import org.eclipse.jface.action.IAction;
import org.eclipse.jface.viewers.IStructuredSelection;

import cn.dockerfoundry.ide.eclipse.server.ui.internal.CloudUiUtil;

public abstract class MenuActionHandler<T> {

    private Class<T> selectionClass;

    protected MenuActionHandler(Class<T> selectionClass) {
        this.selectionClass = selectionClass;
    }

    public List<IAction> getActions(Object context) {
        T selection = getSelectionFromContext(context);
        if (selection != null) {
            return getActionsFromSelection(selection);
        }
        return Collections.emptyList();
    }

    abstract protected List<IAction> getActionsFromSelection(T selection);

    /**
     * Returns a list of applicable context menu actions based on the given
     * context. Always returns a non-null list, although the list may be empty
     * if no actions are applicable to the given context.
     * 
     * @param context to evaluate for the creation of actions. If null, an
     * attempt will be made to obtain the context directly from the Servers view
     * @return non-null list of actions corresponding to the given evaluation
     * context. May be empty if context is invalid.
     */
    @SuppressWarnings("unchecked")
    protected T getSelectionFromContext(Object context) {
        T selection = null;

        // First check if the context is an evaluation context, and attempt to
        // obtain the server module from the context
        if (context instanceof IEvaluationContext) {

            Object evalContext = ((IEvaluationContext) context).getDefaultVariable();

            if (evalContext instanceof List<?>) {
                List<?> content = (List<?>) evalContext;
                if (!content.isEmpty()) {
                    Object obj = content.get(0);
                    if (selectionClass.isAssignableFrom(obj.getClass())) {
                        selection = (T) obj;
                    }
                }
            }
        }

        // Failed to get context selection from context.
        // Try the servers view directly
        if (selection == null) {

            IStructuredSelection strucSelection = CloudUiUtil.getServersViewSelection();
            if (strucSelection != null && !strucSelection.isEmpty()) {
                Object selectObj = strucSelection.getFirstElement();
                if (selectionClass.isAssignableFrom(selectObj.getClass())) {
                    selection = (T) selectObj;
                }
            }
        }

        return selection;
    }

}