com.fuerve.villageelder.client.commandline.commands.Command.java Source code

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Here is the source code for com.fuerve.villageelder.client.commandline.commands.Command.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under 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.
 */
package com.fuerve.villageelder.client.commandline.commands;

import java.io.PrintWriter;
import java.io.Writer;

import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.CommandLineParser;
import org.apache.commons.cli.GnuParser;
import org.apache.commons.cli.HelpFormatter;
import org.apache.commons.cli.Options;
import org.apache.commons.cli.ParseException;

import com.fuerve.villageelder.configuration.PropertyContainer;

/**
 * This abstract class is the basis for command line commands.
 * @author lparker
 *
 */
public abstract class Command {
    private Options options;
    private PropertyContainer propertyContainer;

    /**
     * Initializes a new instance of Command with
     * a set of arguments.
     */
    public Command() {
        options = new Options();
    }

    /**
     * This method may be called by subclasses to aggregate
     * a set of options for a command.
     * @param name The name of the option as it should be
     * specified on the command line.
     * @param hasArg Whether the option has an argument.
     * @param description The long form description of the
     * option.
     */
    protected void addOption(final String name, final boolean hasArg, final String description) {
        if (options == null) {
            options = new Options();
        }
        options.addOption(name, hasArg, description);
    }

    /**
     * This method may be called by subclasses to aggregate
     * a set of options for a command.
     * @param opt The short name of the option.
     * @param longOpt The long name of the option.
     * @param hasArg Whether the option has an argument.
     * @param description The long form description of the
     * option.
     */
    protected void addOption(final String opt, final String longOpt, final boolean hasArg,
            final String description) {
        options.addOption(opt, longOpt, hasArg, description);
    }

    /**
     * This method parses the command line and returns the results
     * in a {@link CommandLine} object.
     * @param args The arguments to parse.
     * @return The {@link CommandLine} object containing the set
     * command line arguments.
     */
    protected CommandLine parseCommandLine(final String[] args) {
        final CommandLineParser parser = new GnuParser();
        CommandLine result;

        try {
            result = parser.parse(options, args);
        } catch (ParseException e) {
            printUsage(new PrintWriter(System.out));
            throw new IllegalArgumentException(e);
        }

        return result;
    }

    /**
     * Triggers the loading of the properties file, which
     * becomes accessible to subclasses via the
     * {@link Command#getProperties()} method.
     */
    protected void loadProperties() {
        propertyContainer = PropertyContainer.getInstance();
    }

    /**
     * Gets the Village Elder property container.
     * @return The property container.
     */
    protected PropertyContainer getProperties() {
        if (propertyContainer == null) {
            loadProperties();
        }

        return propertyContainer;
    }

    /**
     * This method shall be implemented by subclasses to return a
     * simple string containing the name of the command, which is
     * used throughout this framework.
     * @return The string name of this command.
     */
    protected abstract String getCommandName();

    /**
     * This method is the entry point to a command,
     * fully containing the execution path.
     * @return A return code.
     */
    public abstract int execute(final String[] args);

    /**
     * Prints a usage message to a given output {@link Writer}
     * Stolen shamelessly from http://marxsoftware.blogspot.com/2008/11/command-line-parsing-with-apache.html
     * 
     * @param writer The {@link Writer} to which the usage information
     * shall be printed.
     */
    public void printUsage(final Writer writer) {
        final PrintWriter printWriter = new PrintWriter(writer);
        final HelpFormatter formatter = new HelpFormatter();
        formatter.printUsage(printWriter, 80, getCommandName(), options);
        printWriter.close();
    }

    /**
     * Prints a help message to a given output {@link Writer}.
     * Stolen shamelessly from http://marxsoftware.blogspot.com/2008/11/command-line-parsing-with-apache.html
     * 
     * @param printedRowWidth The width of the printed row.
     * @param header The header to print before the help message.
     * @param footer The footer to print after the help message.
     * @param spacesBeforeOption The number of spaces to insert before
     * printing each option.
     * @param spacesBeforeOptionDescription The number of spaces to
     * insert before printing each option's description.
     * @param displayUsage Whether to display basic usage information.
     * @param writer The writer to which the help message shall be
     * written.
     */
    public void printHelp(final boolean displayUsage) {
        final String commandLineSyntax = "VillageElder.sh " + getCommandName();
        final HelpFormatter formatter = new HelpFormatter();
        formatter.printHelp(commandLineSyntax, options);
    }
}