SLF4J: No SLF4J providers were found. SLF4J: Defaulting to no-operation (NOP) logger implementation SLF4J: See https://www.slf4j.org/codes.html#noProviders for further details. Exception in thread "main" org.apache.shiro.config.ConfigurationException: Unable to instantiate class [org.apache.shiro.web.mgt.DefaultWebSecurityManager] for object named 'securityManager'. Please ensure you've specified the fully qualified class name correctly. at org.apache.shiro.config.ReflectionBuilder.createNewInstance(ReflectionBuilder.java:309) at org.apache.shiro.config.ReflectionBuilder$InstantiationStatement.doExecute(ReflectionBuilder.java:927) at org.apache.shiro.config.ReflectionBuilder$Statement.execute(ReflectionBuilder.java:887) at org.apache.shiro.config.ReflectionBuilder$BeanConfigurationProcessor.execute(ReflectionBuilder.java:765) at org.apache.shiro.config.ReflectionBuilder.buildObjects(ReflectionBuilder.java:260) at org.apache.shiro.config.IniSecurityManagerFactory.buildInstances(IniSecurityManagerFactory.java:167) at org.apache.shiro.config.IniSecurityManagerFactory.createSecurityManager(IniSecurityManagerFactory.java:130) at org.apache.shiro.config.IniSecurityManagerFactory.createSecurityManager(IniSecurityManagerFactory.java:108) at org.apache.shiro.config.IniSecurityManagerFactory.createInstance(IniSecurityManagerFactory.java:94) at org.apache.shiro.config.IniSecurityManagerFactory.createInstance(IniSecurityManagerFactory.java:46) at org.apache.shiro.config.IniFactorySupport.createInstance(IniFactorySupport.java:123) at org.apache.shiro.util.AbstractFactory.getInstance(AbstractFactory.java:47) at com.xiu.Quickstart.main(Quickstart.java:26) Caused by: org.apache.shiro.util.UnknownClassException: Unable to load class named [org.apache.shiro.web.mgt.DefaultWebSecurityManager] from the thread context, current, or system/application ClassLoaders. All heuristics have been exhausted. Class could not be found. at org.apache.shiro.util.ClassUtils.forName(ClassUtils.java:152) at org.apache.shiro.util.ClassUtils.newInstance(ClassUtils.java:168) at org.apache.shiro.config.ReflectionBuilder.createNewInstance(ReflectionBuilder.java:302) ... 12 more

这个异常是因为 Shiro 框架没有找到 SLF4J（Simple Logging Facade for Java）的实现类，导致默认使用了 NOP（No-Operation）日志记录器实现。

可以通过以下几个步骤解决这个异常：

1. 确保在应用程序的 classpath 下存在 SLF4J 的实现类，比如 Logback、Log4j 等。
2. 确认应用程序中已经正确引入了 SLF4J 的依赖，比如以下 Maven 依赖：

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-api</artifactId>
    <version>1.7.30</version>
</dependency>
<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.2.3</version>
</dependency>

3. 确认 SLF4J 的配置文件是否正确，比如 logback.xml 或者 log4j.properties 等。

如果以上步骤都没有解决问题，可以尝试修改 Shiro 的日志记录器实现类，比如使用 Logback 作为日志记录器实现：

# 修改 Shiro 的日志记录器实现类为 Logback
log4j.logger.org.apache.shiro=INFO, stdout
log4j.logger.org.apache.shiro.util.ThreadContext=INFO, stdout
log4j.logger.org.apache.shiro.realm=INFO, stdout
log4j.logger.org.apache.shiro.web=INFO, stdout
log4j.logger.org.apache.shiro.cache=INFO, stdout
log4j.logger.org.apache.shiro.session=INFO, stdout

# Logback 配置文件，可以将日志输出到控制台
<configuration>
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <logger name="org.apache.shiro" level="INFO"/>
    <root level="DEBUG">
        <appender-ref ref="STDOUT" />
    </root>
</configuration>