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package org.apache.juneau.rest;

import java.text.*;
import java.util.logging.*;

import javax.servlet.http.*;

import org.apache.juneau.json.*;

/**
 * Logging utility class.
 * 
 * <h5 class='section'>See Also:</h5>
 * <ul>
 *    <li class='jf'>{@link RestContext#REST_logger}
 *    <li class='link'><a class="doclink" href="../../../../overview-summary.html#juneau-rest-server.LoggingAndErrorHandling">Overview &gt; juneau-rest-server &gt; Logging and Error Handling</a>
 * </ul>
 */
public interface RestLogger {

   /**
    * Represents no RestLogger.
    * 
    * <p>
    * Used on annotation to indicate that the value should be inherited from the parent class, and
    * ultimately {@link BasicRestLogger} if not specified at any level.
    */
   public interface Null extends RestLogger {}

   /**
    * Log a message to the logger.
    * 
    * @param level The log level.
    * @param cause The cause.
    * @param msg The message to log.
    * @param args Optional {@link MessageFormat}-style arguments.
    */
   public void log(Level level, Throwable cause, String msg, Object...args);

   /**
    * Log a message.
    * 
    * @param level The log level.
    * @param msg The message to log.
    * @param args Optional {@link MessageFormat}-style arguments.
    */
   public void log(Level level, String msg, Object...args);

   /**
    * Same as {@link #log(Level, String, Object...)} excepts runs the arguments through {@link JsonSerializer#DEFAULT_LAX_READABLE}.
    * 
    * <p>
    * Serialization of arguments do not occur if message is not logged, so it's safe to use this method from within
    * debug log statements.
    * 
    * <h5 class='section'>Example:</h5>
    * <p class='bcode'>
    *    logObjects(<jsf>DEBUG</jsf>, <js>"Pojo contents:\n{0}"</js>, myPojo);
    * </p>
    * 
    * @param level The log level.
    * @param msg The message to log.
    * @param args Optional {@link MessageFormat}-style arguments.
    */
   public void logObjects(Level level, String msg, Object...args);

   /**
    * Callback method for logging errors during HTTP requests.
    * 
    * <p>
    * Typically, subclasses will override this method and log errors themselves.
    * 
    * <p>
    * The default implementation simply logs errors to the <code>RestServlet</code> logger.
    * 
    * <p>
    * Here's a typical implementation showing how stack trace hashing can be used to reduce log file sizes...
    * <p class='bcode'>
    *    <jk>protected void</jk> onError(HttpServletRequest req, HttpServletResponse res, RestException e, <jk>boolean</jk> noTrace) {
    *       String qs = req.getQueryString();
    *       String msg = <js>"HTTP "</js> + req.getMethod() + <js>" "</js> + e.getStatus() + <js>" "</js> + req.getRequestURI() + (qs == <jk>null</jk> ? <js>""</js> : <js>"?"</js> + qs);
    *       <jk>int</jk> c = e.getOccurrence();
    * 
    *       <jc>// REST_useStackTraceHashes is disabled, so we have to log the exception every time.</jc>
    *       <jk>if</jk> (c == 0)
    *          myLogger.log(Level.<jsf>WARNING</jsf>, <jsm>format</jsm>(<js>"[%s] %s"</js>, e.getStatus(), msg), e);
    * 
    *       <jc>// This is the first time we've countered this error, so log a stack trace
    *       // unless ?noTrace was passed in as a URL parameter.</jc>
    *       <jk>else if</jk> (c == 1 &amp;&amp; ! noTrace)
    *          myLogger.log(Level.<jsf>WARNING</jsf>, <jsm>format</jsm>(<js>"[%h.%s.%s] %s"</js>, e.hashCode(), e.getStatus(), c, msg), e);
    * 
    *       <jc>// This error occurred before.
    *       // Only log the message, not the stack trace.</jc>
    *       <jk>else</jk>
    *          myLogger.log(Level.<jsf>WARNING</jsf>, <jsm>format</jsm>(<js>"[%h.%s.%s] %s, %s"</js>, e.hashCode(), e.getStatus(), c, msg, e.getLocalizedMessage()));
    *    }
    * </p>
    * 
    * @param req The servlet request object.
    * @param res The servlet response object.
    * @param e Exception indicating what error occurred.
    */
   public void onError(HttpServletRequest req, HttpServletResponse res, RestException e);
}