Log4j2与JNDI结合

在Log4j和JNDI结合一文中介绍了在Web应用中如何通过JNDI和log4j结合来指定配置文件地址和日志文件日志。
这里介绍Web应用中log4j2如何和JNDI结合达到相同的目的。
这里也要分2个部分：
第一步是指定配置文件地址，同样要定制自己的listener来初始化log4j2
JndiLog4j2ConfigListener实现

...
import org.apache.logging.log4j.core.config.Configurator;
...
    public static final String CONFIG_FILE_URL = "log4jConfiguration";
    public static final String CONFIG_FILENAME_PARAM = "log4jFilename";
    private LoggerContext loggerContext;

    public void contextInitialized(ServletContextEvent servletContextEvent) {
       ServletContext sc = servletContextEvent.getServletContext();
       String location = sc.getInitParameter(CONFIG_FILE_URL);
       String filename = sc.getInitParameter(CONFIG_FILENAME_PARAM);
       if(StringUtils.isBlank(location) || StringUtils.isBlank(filename)){
           sc.log("invalid config file location or filename, location: " + location + " filename: " + filename);
       }
       try{
          InitialContext ic = new InitialContext();
          URL log4jURL = (URL) context.lookup(location);
          location = log4jURL.toExternalForm();
          location = location + file.separator + filename;
       String contextName = servletContext.getServletContextName();
       Classloader classloader = this.getClass().getClassloader();
       loggerContext = Configurator.initialize(contextName, classloader, location);
       } catch (NamingException ex){
          throw new IllegalArgumentException("Invaild log4j config: " + ex.getMessage());
       }
    }

    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();
        servletContext.log("Log4jConfigurationListener - Shutting down log4j");
        if (loggerContext != null) 
             Configurator.shutdown(loggerContext);
    }

Web配置

<context-param>     
      <param-name>log4jConfiguration</param-name>     
      <param-value>jndi:java:/comp/env/config_dir</param-value>     
  </context-param>     
 <context-param>     
      <param-name>log4jFilename</param-name>     
      <param-value>log4j2-demo.xml</param-value>     
  </context-param>   

  <listener>     
      <listener-class>com.demo.JndiLog4j2ConfigListener</listener-class>     
  </listener> 

<resource-ref>
     <res-ref-name> config_dir </res-ref-name>
    <res-type> java.net.URL </res-type>
    <res-auth> Container </res-auth>
 </resource-ref>

第二步是
定制自己的appender，这里参考RollingRandomAccessFileAppender来通过JNDI指定日志文件地址

@Plugin(name = "JndiRollingRandomAccessFile", category = "Core", elementType = "appender", printObject = true)
public final class JndiRollingRandomAccessFileAppender extends AbstractOutputStreamAppender<JndiRollingRandomAccessFileManager> {

    private final String fileName;
    private final String filePattern;
    private final Object advertisement;
    private final Advertiser advertiser;

    private static String LOG_DIR_URL = "java:comp/env/DEFAULT_URL";

    private JndiRollingRandomAccessFileAppender(final String name, final Layout<? extends Serializable> layout,
            final Filter filter, final JndiRollingRandomAccessFileManager manager, final String fileName,
            final String filePattern, final boolean ignoreExceptions,
            final boolean immediateFlush, final int bufferSize, final Advertiser advertiser) {
        super(name, layout, filter, ignoreExceptions, immediateFlush, manager);
        if (advertiser != null) {
            final Map<String, String> configuration = new HashMap<>(layout.getContentFormat());
            configuration.put("contentType", layout.getContentType());
            configuration.put("name", name);
            advertisement = advertiser.advertise(configuration);
        } else {
            advertisement = null;
        }
        this.fileName = fileName;
        this.filePattern = filePattern;
        this.advertiser = advertiser;
    }

    @Override
    public void stop() {
        super.stop();
        if (advertiser != null) {
            advertiser.unadvertise(advertisement);
        }
    }

    /**
     * Write the log entry rolling over the file when required.
     *
     * @param event The LogEvent.
     */
    @Override
    public void append(final LogEvent event) {
        final JndiRollingRandomAccessFileManager manager = getManager();
        manager.checkRollover(event);

        // Leverage the nice batching behaviour of async Loggers/Appenders:
        // we can signal the file manager that it needs to flush the buffer
        // to disk at the end of a batch.
        // From a user's point of view, this means that all log events are
        // _always_ available in the log file, without incurring the overhead
        // of immediateFlush=true.
        manager.setEndOfBatch(event.isEndOfBatch()); // FIXME manager's EndOfBatch threadlocal can be deleted

        // LOG4J2-1292 utilize gc-free Layout.encode() method: taken care of in superclass
        super.append(event);
    }

    /**
     * Returns the File name for the Appender.
     *
     * @return The file name.
     */
    public String getFileName() {
        return fileName;
    }

    /**
     * Returns the file pattern used when rolling over.
     *
     * @return The file pattern.
     */
    public String getFilePattern() {
        return filePattern;
    }

    /**
     * Returns the size of the file manager's buffer.
     * @return the buffer size
     */
    public int getBufferSize() {
        return getManager().getBufferSize();
    }

    /**
     * Create a JndiRollingRandomAccessFileAppender.
     *
     * @param parent The name of the dir that the file is actively written to.
     *            (required).
     * @param fileName The name of the file that is actively written to.
     *            (required).
     * @param filePattern The pattern of the file name to use on rollover.
     *            (required).
     * @param append If true, events are appended to the file. If false, the
     *            file is overwritten when opened. Defaults to "true"
     * @param name The name of the Appender (required).
     * @param immediateFlush When true, events are immediately flushed. Defaults
     *            to "true".
     * @param bufferSizeStr The buffer size, defaults to {@value JndiRollingRandomAccessFileManager#DEFAULT_BUFFER_SIZE}.
     * @param policy The triggering policy. (required).
     * @param strategy The rollover strategy. Defaults to
     *            DefaultRolloverStrategy.
     * @param layout The layout to use (defaults to the default PatternLayout).
     * @param filter The Filter or null.
     * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
     *               they are propagated to the caller.
     * @param advertise "true" if the appender configuration should be
     *            advertised, "false" otherwise.
     * @param advertiseURI The advertised URI which can be used to retrieve the
     *            file contents.
     * @param config The Configuration.
     * @return A JndiRollingRandomAccessFileAppender.
     */
    @PluginFactory
    public static JndiRollingRandomAccessFileAppender createAppender(
            @PluginAttribute("parent") final String parent,
            @PluginAttribute("fileName") final String fileName,
            @PluginAttribute("filePattern") final String filePattern,
            @PluginAttribute("append") final String append,
            @PluginAttribute("name") final String name,
            @PluginAttribute("immediateFlush") final String immediateFlush,
            @PluginAttribute("bufferSize") final String bufferSizeStr,
            @PluginElement("Policy") final TriggeringPolicy policy,
            @PluginElement("Strategy") RolloverStrategy strategy,
            @PluginElement("Layout") Layout<? extends Serializable> layout,
            @PluginElement("Filter") final Filter filter,
            @PluginAttribute("ignoreExceptions") final String ignore,
            @PluginAttribute("advertise") final String advertise,
            @PluginAttribute("advertiseURI") final String advertiseURI,
            @PluginConfiguration final Configuration config) {

        final boolean isAppend = Booleans.parseBoolean(append, true);
        final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
        final boolean isFlush = Booleans.parseBoolean(immediateFlush, true);
        final boolean isAdvertise = Boolean.parseBoolean(advertise);
        final int bufferSize = Integers.parseInt(bufferSizeStr, JndiRollingRandomAccessFileManager.DEFAULT_BUFFER_SIZE);

        if (name == null) {
            LOGGER.error("No name provided for FileAppender");
            return null;
        }

        if (parent == null) {
            LOGGER.error("No parent folder was provided for FileAppender with name " + name);
            return null;
        }

        if (fileName == null) {
            LOGGER.error("No filename was provided for FileAppender with name " + name);
            return null;
        }
        String dir = null;
        try{
          InitialContext ic = new InitialContext();
          URL log4jURL = (URL) context.lookup(parent);
          dir = log4jURL.toExternalForm();
        } catch (NamingException ex){
            LOGGER.error("fail to fetch parent dir for FileAppender with name " + name);
            return null;
        }

        if (filePattern == null) {
            LOGGER.error("No filename pattern provided for FileAppender with name " + name);
            return null;
        }

        if (policy == null) {
            LOGGER.error("A TriggeringPolicy must be provided");
            return null;
        }

        if (strategy == null) {
            strategy = DefaultRolloverStrategy.createStrategy(null, null, null,
                    String.valueOf(Deflater.DEFAULT_COMPRESSION), null, true, config);
        }

        if (layout == null) {
            layout = PatternLayout.createDefaultLayout();
        }

        final JndiRollingRandomAccessFileManager manager = JndiRollingRandomAccessFileManager.getJndiRollingRandomAccessFileManager(
                parent + File.separator + fileName, parent + File.separator + filePattern, isAppend, isFlush, bufferSize, policy, strategy, advertiseURI, layout);
        if (manager == null) {
            return null;
        }

        return new JndiRollingRandomAccessFileAppender(name, layout, filter, manager,
                parent + File.separator + fileName, parent + File.separator + filePattern, ignoreExceptions, isFlush, bufferSize,
                isAdvertise ? config.getAdvertiser() : null);
    }
}

配置文件：

<JndiRollingRandomAccessFile name="RollingFile" parent="java:comp/env/DEFAULT_URL" fileName="sample.log"    
                 filePattern="$${date:yyyy-MM}/app-%d{MM-dd-yyyy}-%i.log.gz" immediateFlush="false" append="true">    
      <PatternLayout pattern="%d{yyyy.MM.dd 'at' HH:mm:ss z} %-5level %class{36} %L %M - %msg%xEx%n"/>    
      <SizeBasedTriggeringPolicy size="50 MB" />    
      <DefaultRolloverStrategy max="10" />
    </JndiRollingRandomAccessFile>  

注1：log4j2的基本使用参考
注2：log4j2的配置文件号称可以替换参数来定制路径，我使用失败了，最近没空研究log4j2的代码，以后再看看，有知道的也请指教。