com.jbrisbin.vpc.jobsched.patch.PatchMessageHandler.java Source code

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Here is the source code for com.jbrisbin.vpc.jobsched.patch.PatchMessageHandler.java

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/*
 * Copyright 2010 by J. Brisbin <jon@jbrisbin.com>
 *
 * Licensed 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.jbrisbin.vpc.jobsched.patch;

import difflib.DiffUtils;
import difflib.Patch;
import difflib.PatchFailedException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

import java.io.*;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;

/**
 * @author Jon Brisbin <jon.brisbin@npcinternational.com>
 */
@SuppressWarnings({ "unchecked" })
public class PatchMessageHandler implements ApplicationContextAware {

    private final Logger log = LoggerFactory.getLogger(getClass());

    private SimpleDateFormat fmt = new SimpleDateFormat("yyyyMMdd.HHmmss");
    private ApplicationContext appCtx;

    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.appCtx = applicationContext;
    }

    public void handleMessage(final PatchMessage msg) {

        if (null != msg.getFile()) {
            // Read original file
            List<String> original = new ArrayList<String>();
            File originalFile = new File(msg.getFile());
            try {
                BufferedReader reader = new BufferedReader(new FileReader(originalFile));
                String line = null;
                while (null != (line = reader.readLine())) {
                    original.add(line);
                }
                reader.close();
            } catch (FileNotFoundException e) {
                log.error(e.getMessage(), e);
            } catch (IOException e) {
                log.error(e.getMessage(), e);
            }
            if (log.isDebugEnabled()) {
                log.debug("Patching original file: " + original);
            }

            // Patch it
            Patch patch = DiffUtils.parseUnifiedDiff(msg.getDiff());
            try {
                List<String> updated = (List<String>) DiffUtils.patch(original, patch);
                File tmp = File.createTempFile("patcher_", "patched");
                BufferedWriter writer = new BufferedWriter(new FileWriter(tmp));
                for (String line : updated) {
                    writer.write(line + "\n");
                }
                writer.flush();
                writer.close();

                // Backup existing file
                File basedir = originalFile.getParentFile();
                if (basedir.canWrite()) {
                    File backup = new File(originalFile.getParentFile(),
                            originalFile.getName() + ".bkp." + fmt.format(Calendar.getInstance().getTime()));
                    originalFile.renameTo(backup);
                    // Replace with patched version
                    tmp.renameTo(originalFile);
                }

            } catch (PatchFailedException e) {
                log.error(e.getMessage(), e);
            } catch (IOException e) {
                log.error(e.getMessage(), e);
            }
        }

    }
}