Spring-jclソース(3)--LogAdapterがLogオブジェクトを作成するプロセス

/*       Log4j Logger */
	private static final String LOG4J_SPI = "org.apache.logging.log4j.spi.ExtendedLogger";

	private static final String LOG4J_SLF4J_PROVIDER = "org.apache.logging.slf4j.SLF4JProvider";

	/*         ，                */
	private static final String SLF4J_SPI = "org.slf4j.spi.LocationAwareLogger";

	/* SLF4J Logger  */
	private static final String SLF4J_API = "org.slf4j.Logger";

	/* LogApi   */
	private static final LogApi logApi;

	static {
		/*      LOG4J_SPI  */
		if (isPresent(LOG4J_SPI)) {
			/*      LOG4J_SLF4J_PROVIDER SLF4J_SPI   */
			if (isPresent(LOG4J_SLF4J_PROVIDER) && isPresent(SLF4J_SPI)) {
				// log4j-to-slf4j bridge -> we'll rather go with the SLF4J SPI;
				// however, we still prefer Log4j over the plain SLF4J API since
				// the latter does not have location awareness support.
				/* log4j-to-slf4j  ，        slf4j SPI,  ，      log4j      slf4j API，            。 */
				logApi = LogApi.SLF4J_LAL;
			}
			else {
				// Use Log4j 2.x directly, including location awareness support
				/*     log4j 2.x，         */
				logApi = LogApi.LOG4J;
			}
		}
		/*      SLF4J_SPI  */
		else if (isPresent(SLF4J_SPI)) {
			// Full SLF4J SPI including location awareness support
			/*    SLF4J SPI，         */
			logApi = LogApi.SLF4J_LAL;
		}
		/*      SLF4J_API  */
		else if (isPresent(SLF4J_API)) {
			// Minimal SLF4J API without location awareness support
			/*    SLF4J API           */
			logApi = LogApi.SLF4J;
		}
		else {
			// java.util.logging as default
			/* java.util.logging   logApi */
			logApi = LogApi.JUL;
		}
	}