org.apache.juli.logging.Log

package org.apache.juli.logging;

/**
 * 日志接口API。为了能够被LogFactory实例，实现这个Log接口的类必须要包含
 * 含有单个字符串作为参数的构造函数，这个字符串参数用来作为日志的名字。
 * Log含有6个日志级别:
 * trace
 * debug
 * info
 * warn
 * error
 * fatal
 *
 * The mapping of these log levels to the concepts used by the underlying
 * logging system is implementation dependent.
 * The implementation should ensure, though, that this ordering behaves
 * as expected.</p>
 *
 * <p>Performance is often a logging concern.
 * By examining the appropriate property,
 * a component can avoid expensive operations (producing information
 * to be logged).</p>
 *
 * <p> For example,
 * <code><pre>
 *    if (log.isDebugEnabled()) {
 *        ... do something expensive ...
 *        log.debug(theResult);
 *    }
 * </pre></code>
 * </p>
 *
 * <p>Configuration of the underlying logging system will generally be done
 * external to the Logging APIs, through whatever mechanism is supported by
 * that system.</p>
 *
 * @author <a href="mailto:sanders@apache.org">Scott Sanders</a>
 * @author Rod Waldhoff
 */
public interface Log {


    // ----------------------------------------------------- Logging Properties


    /**
     * <p> Is debug logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than debug. </p>
     */
    public boolean isDebugEnabled();


    /**
     * <p> Is error logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than error. </p>
     */
    public boolean isErrorEnabled();


    /**
     * <p> Is fatal logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than fatal. </p>
     */
    public boolean isFatalEnabled();


    /**
     * <p> Is info logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than info. </p>
     */
    public boolean isInfoEnabled();


    /**
     * <p> Is trace logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than trace. </p>
     */
    public boolean isTraceEnabled();


    /**
     * <p> Is warn logging currently enabled? </p>
     *
     * <p> Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than warn. </p>
     */
    public boolean isWarnEnabled();


    // -------------------------------------------------------- Logging Methods


    /**
     * <p> Log a message with trace log level. </p>
     *
     * @param message log this message
     */
    public void trace(Object message);


    /**
     * <p> Log an error with trace log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void trace(Object message, Throwable t);


    /**
     * <p> Log a message with debug log level. </p>
     *
     * @param message log this message
     */
    public void debug(Object message);


    /**
     * <p> Log an error with debug log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void debug(Object message, Throwable t);


    /**
     * <p> Log a message with info log level. </p>
     *
     * @param message log this message
     */
    public void info(Object message);


    /**
     * <p> Log an error with info log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void info(Object message, Throwable t);


    /**
     * <p> Log a message with warn log level. </p>
     *
     * @param message log this message
     */
    public void warn(Object message);


    /**
     * <p> Log an error with warn log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void warn(Object message, Throwable t);


    /**
     * <p> Log a message with error log level. </p>
     *
     * @param message log this message
     */
    public void error(Object message);


    /**
     * <p> Log an error with error log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void error(Object message, Throwable t);


    /**
     * <p> Log a message with fatal log level. </p>
     *
     * @param message log this message
     */
    public void fatal(Object message);


    /**
     * <p> Log an error with fatal log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void fatal(Object message, Throwable t);


}