edu.cornell.mannlib.vitro.webapp.config.RevisionInfoSetup.java Source code

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Here is the source code for edu.cornell.mannlib.vitro.webapp.config.RevisionInfoSetup.java

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/* $This file is distributed under the terms of the license in /doc/license.txt$ */

package edu.cornell.mannlib.vitro.webapp.config;

import static edu.cornell.mannlib.vitro.webapp.config.RevisionInfoBean.DUMMY_BEAN;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import edu.cornell.mannlib.vitro.webapp.config.RevisionInfoBean.LevelRevisionInfo;
import edu.cornell.mannlib.vitro.webapp.startup.StartupStatus;

/**
 * <pre>
 * Read the revision information, and store it in the servlet context.
 * 
 * - The revision information is in a file in the classpath. 
 * - The name of the file is in RESOURCE_PATH, below.
 * - The first line is the build date, with a format as in DATE_FORMAT, below.
 * - Each additional non-blank line holds revision info for one application level:
 *    - level info is from inner (vitro) to outer (top-level product).
 *    - level info appears as product name, release name and revision level, 
 *        delimited by " ~ ". 
 *    - additional white space before and after info values is ignored.
 * 
 * Example file:
 *    2010-11-14 23:58:00
 *    vitroCore ~ Release 1.1 ~ 6604
 *    nihvivo ~ Release 1.1 ~ 1116
 * </pre>
 */
public class RevisionInfoSetup implements ServletContextListener {
    private static final Log log = LogFactory.getLog(RevisionInfoSetup.class);

    private static final Pattern LEVEL_INFO_PATTERN = Pattern.compile("(.+) ~ (.+) ~ (.+)");

    static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";
    static final String RESOURCE_PATH = "/WEB-INF/resources/revisionInfo.txt";

    /**
     * On startup, read the revision info from the resource file in the
     * classpath.
     * 
     * If we can't find the file, or can't parse it, store an empty bean.
     * 
     * Don't allow any Exceptions to percolate up past this point.
     */
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        ServletContext context = sce.getServletContext();
        RevisionInfoBean bean;
        try {
            List<String> lines = readRevisionInfo(context);
            bean = parseRevisionInformation(lines);
        } catch (Exception e) {
            StartupStatus.getBean(context).warning(this, "Failed to load the revision info", e);
            bean = DUMMY_BEAN;
        }

        RevisionInfoBean.setBean(sce.getServletContext(), bean);
    }

    private List<String> readRevisionInfo(ServletContext context) throws IOException {
        BufferedReader reader = null;
        try {
            reader = openRevisionInfoReader(context);
            return readSignificantLines(reader);
        } finally {
            closeReader(reader);
        }
    }

    private BufferedReader openRevisionInfoReader(ServletContext context) throws FileNotFoundException {
        InputStream stream = context.getResourceAsStream(RESOURCE_PATH);
        if (stream == null) {
            throw new FileNotFoundException("Can't find a resource in the webapp at '" + RESOURCE_PATH + "'.");
        } else {
            return new BufferedReader(new InputStreamReader(stream));
        }
    }

    private List<String> readSignificantLines(BufferedReader reader) throws IOException {
        List<String> lines = new ArrayList<String>();

        String line = null;
        while (null != (line = reader.readLine())) {
            line = line.trim();
            if ((!line.isEmpty()) && (!line.startsWith("#"))) {
                lines.add(line);
            }
        }

        return lines;
    }

    private void closeReader(Reader reader) {
        if (reader != null) {
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private RevisionInfoBean parseRevisionInformation(List<String> lines) throws ParseException {
        checkValidNumberOfLines(lines);
        String dateLine = lines.get(0);
        List<String> levelLines = lines.subList(1, lines.size());

        Date buildDate = parseDateLine(dateLine);
        List<LevelRevisionInfo> levelInfos = parseLevelLines(levelLines);
        return new RevisionInfoBean(buildDate, levelInfos);
    }

    private void checkValidNumberOfLines(List<String> lines) throws ParseException {
        if (lines.isEmpty()) {
            throw new ParseException("The revision info resource file contains no data.", 0);
        }
    }

    private Date parseDateLine(String dateLine) throws ParseException {
        return new SimpleDateFormat(DATE_FORMAT).parse(dateLine);
    }

    private List<LevelRevisionInfo> parseLevelLines(List<String> levelLines) throws ParseException {
        List<LevelRevisionInfo> infos = new ArrayList<LevelRevisionInfo>();
        for (String line : levelLines) {
            Matcher m = LEVEL_INFO_PATTERN.matcher(line);
            if (m.matches()) {
                String name = m.group(1).trim();
                String release = m.group(2).trim();
                String revision = m.group(3).trim();
                infos.add(new LevelRevisionInfo(name, release, revision));
            } else {
                throw new ParseException("Failed to parse the revision info in '" + line + "'", 0);
            }
        }
        return infos;
    }

    /** On shutdown, clean up. */
    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        RevisionInfoBean.removeBean(sce.getServletContext());
    }

}