SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/C:/Users/oxas4e/.gradle/caches/modules-2/files-2.1/org.slf4j/slf4j-simple/1.6.1/58e59bfb3e247097b8122243b3bfe0049c8cfae8/slf4j-simple-1.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/C:/Users/oxas4e/.gradle/caches/modules-2/files-2.1/ch.qos.logback/logback-classic/1.2.3/7c4f3c474fb2c041d8028740440937705ebb473a/logback-classic-1.2.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.SimpleLoggerFactory]
Exception in thread "main" java.lang.IllegalArgumentException: LoggerFactory is not a Logback LoggerContext but Logback is on the classpath. Either remove Logback or the competing implementation (class org.slf4j.impl.SimpleLoggerFactory loaded from file:/C:/Users/oxas4e/.gradle/caches/modules-2/files-2.1/org.slf4j/slf4j-simple/1.6.1/58e59bfb3e247097b8122243b3bfe0049c8cfae8/slf4j-simple-1.6.1.jar). If you are using WebLogic you will need to add 'org.slf4j' to prefer-application-packages in WEB-INF/weblogic.xml: org.slf4j.impl.SimpleLoggerFactory
    at org.springframework.util.Assert.instanceCheckFailed(Assert.java:655)
    at org.springframework.util.Assert.isInstanceOf(Assert.java:555)
    at org.springframework.boot.logging.logback.LogbackLoggingSystem.getLoggerContext(LogbackLoggingSystem.java:280)
    at org.springframework.boot.logging.logback.LogbackLoggingSystem.beforeInitialize(LogbackLoggingSystem.java:104)
    at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationStartingEvent(LoggingApplicationListener.java:219)
    at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationEvent(LoggingApplicationListener.java:200)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)
    at org.springframework.boot.context.event.EventPublishingRunListener.starting(EventPublishingRunListener.java:70)
    at org.springframework.boot.SpringApplicationRunListeners.starting(SpringApplicationRunListeners.java:47)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:302)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1204)
    at 

从上面的日志中我们可以看出一下几点：

1. 项目中存在多个slf4j bindings

SLF4J: Class path contains multiple SLF4J bindings.

2. slf4j选择了slf4j-simple

SLF4J: Actual binding is of type [org.slf4j.impl.SimpleLoggerFactory]

3. 由于ch.qos.logback:logback-classic在classpath中，spring-boot会优先加载logback-classi作为日志打印工具，从报错的打印堆栈就能看出，报错是从spring-boot那打上来的。

private static final Map<String, String> SYSTEMS;

    static {
        Map<String, String> systems = new LinkedHashMap<>();
        systems.put("ch.qos.logback.core.Appender", "org.springframework.boot.logging.logback.LogbackLoggingSystem");
        systems.put("org.apache.logging.log4j.core.impl.Log4jContextFactory",
                "org.springframework.boot.logging.log4j2.Log4J2LoggingSystem");
        systems.put("java.util.logging.LogManager", "org.springframework.boot.logging.java.JavaLoggingSystem");
        SYSTEMS = Collections.unmodifiableMap(systems);
    }

然而，slf4j又不是选的logback-classic做slf4j的binding，这里就会出错了，看报错说：
LoggerFactory is not a Logback LoggerContext but Logback is on the classpath

LoggerFactory不是Logback LoggerContext，但是Logback 却在classpath中。所以，我们要从classpath中移除logback-classic。（怎么移除？你用gradle的话就在gradle.build中移除，用maven的话就在pom.xml中移除）