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。