LogModule.java

/**
 * XWeb project
 * https://github.com/abdollahpour/xweb
 * Hamed Abdollahpour - 2013
 */

package ir.xweb.module;

import org.apache.commons.fileupload.FileItem;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.Math;
import java.util.Map;
import java.io.File;

public class LogModule extends Module {

    private final static Logger logger = LoggerFactory.getLogger(LogModule.class);

    private final static String PARAM_LOG_FILE = "file.log";

    private final static String SESSION_LAST_POSITION = "module_log_position_";

    private final static int MAX_READ = 30 * 1024;

    private final File log;

    public LogModule(
            final Manager manager,
            final ModuleInfo info,
            final ModuleParam properties) throws ModuleException {

        super(manager, info, properties);

        log = properties.getFile(PARAM_LOG_FILE);
    }

    @Override
    public void process(
            final ServletContext context,
            final HttpServletRequest request,
            final HttpServletResponse response,
            final ModuleParam params,
            final Map<String, FileItem> files) throws IOException {

        /** We have different log history for different IDs, so we can have different HTMLs **/
        final String id = params.getString("id", "0");

        if(log != null && log.exists()) {
            response.setContentType("text/plain");

            long last = log.lastModified();
            long len = log.length();

            Long position = (Long) request.getSession().getAttribute(SESSION_LAST_POSITION + id);

            // init
            if(position == null) {
                position = Math.max(0, len - MAX_READ);
            }

            final PrintWriter writer = response.getWriter();
            final FileReader reader = new FileReader(log);
            if(position > 0) {
                reader.skip(position);
            }

            char[] buffer = new char[1024];
            int size;

            while((size = reader.read(buffer)) > 0) {
                writer.write(buffer, 0, size);
                position += size;
            }

            request.getSession().setAttribute(SESSION_LAST_POSITION + id, position);

            reader.close();
        } else {
            logger.error("Log file not found: " + log);
        }
    }
}