如果最近你也在学习SpringBoot，当项目运行时，你有可能会遇到这样的异常：java.lang.NoClassDefFoundError: org/apache/juli/logging/LogFactory

一、异常描述：

1 org.springframework.context.ApplicationContextException: Unable to start embedded
2 container; nested exception is java.lang.NoClassDefFoundError:
3 org/apache/juli/logging/LogFactory
4     at
5 org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh
6 (EmbeddedWebApplicationContext.java:137) ~[spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
7     at org.springframework.context.support.AbstractApplicationContext.refresh
8 (AbstractApplicationContext.java:537) ~[spring-context-4.3.9.RELEASE.jar:4.3.9.RELEASE]
9     at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh
10 (EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
11     at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:762)
12 [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
13     at org.springframework.boot.SpringApplication.refreshContext
14 (SpringApplication.java:372) [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
15     at org.springframework.boot.SpringApplication.run(SpringApplication.java:316)
16 [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
17     at org.springframework.boot.SpringApplication.run(SpringApplication.java:1187)
18 [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
19     at org.springframework.boot.SpringApplication.run(SpringApplication.java:1176)
20 [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
21     at com.fhcq.MySpringBootApplication.main(MySpringBootApplication.java:10)
22 [classes/:na]
23 Caused by: java.lang.NoClassDefFoundError: org/apache/juli/logging/LogFactory
24     at org.apache.catalina.util.LifecycleBase.<clinit>(LifecycleBase.java:41) ~
25 [catalina.jar:8.5.23]
26     at
27 org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.
28 getEmbeddedServletContainer(TomcatEmbeddedServletContainerFactory.java:167) ~[spring-boot-
29 1.4.7.RELEASE.jar:1.4.7.RELEASE]
30     at
31 org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.
32 createEmbeddedServletContainer(EmbeddedWebApplicationContext.java:164) ~[spring-boot-
33 1.4.7.RELEASE.jar:1.4.7.RELEASE]
34     at
35 org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh
36 (EmbeddedWebApplicationContext.java:134) ~[spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
37     ... 8 common frames omitted
38 Caused by: java.lang.ClassNotFoundException: org.apache.juli.logging.LogFactory
39     at java.net.URLClassLoader.findClass(Unknown Source) ~[na:1.8.0_144]
40     at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
41     at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
42     at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
43     ... 12 common frames omitted

二、错误分析：

很显然，缺少 tomcat-juli.jar，找不到类 org.apache.juli.logging.LogFactory，而此jar包在Tomcat安装目录的bin目录下。

三、解决办法：

在Maven工程的pom文件中加入 tomcat-juli.jar 的依赖：

1 <dependency>
2     <groupId>org.apache.tomcat</groupId>
3     <artifactId>tomcat-juli</artifactId>
4     <version>7.0.27</version>
5 </dependency>

然而，将 tomcat-juli-7.0.27.jar 版本的依赖加入工程后，运行工程发现Console控制台报出新的异常：

java.lang.NoClassDefFoundError: org/apache/juli/WebappProperties

一、异常描述：

1 org.springframework.context.ApplicationContextException: Unable to start embedded
2 container; nested exception is java.lang.NoClassDefFoundError:
3 org/apache/juli/WebappProperties
4     at
5 org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh
6 (EmbeddedWebApplicationContext.java:137) ~[spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
7     at org.springframework.context.support.AbstractApplicationContext.refresh
8 (AbstractApplicationContext.java:537) ~[spring-context-4.3.9.RELEASE.jar:4.3.9.RELEASE]
9     at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh
10 (EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
11     at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:762)
12 [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
13     at org.springframework.boot.SpringApplication.refreshContext
14 (SpringApplication.java:372) [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
15     at org.springframework.boot.SpringApplication.run(SpringApplication.java:316)
16 [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
17     at org.springframework.boot.SpringApplication.run(SpringApplication.java:1187)
18 [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
19     at org.springframework.boot.SpringApplication.run(SpringApplication.java:1176)
20 [spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
21     at com.fhcq.MySpringBootApplication.main(MySpringBootApplication.java:10)
22 [classes/:na]
23 Caused by: java.lang.NoClassDefFoundError: org/apache/juli/WebappProperties
24     at java.lang.ClassLoader.defineClass1(Native Method) ~[na:1.8.0_144]
25     at java.lang.ClassLoader.defineClass(Unknown Source) ~[na:1.8.0_144]
26     at java.security.SecureClassLoader.defineClass(Unknown Source) ~[na:1.8.0_144]
27     at java.net.URLClassLoader.defineClass(Unknown Source) ~[na:1.8.0_144]
28     at java.net.URLClassLoader.access$100(Unknown Source) ~[na:1.8.0_144]
29     at java.net.URLClassLoader$1.run(Unknown Source) ~[na:1.8.0_144]
30     at java.net.URLClassLoader$1.run(Unknown Source) ~[na:1.8.0_144]
31     at java.security.AccessController.doPrivileged(Native Method) ~[na:1.8.0_144]
32     at java.net.URLClassLoader.findClass(Unknown Source) ~[na:1.8.0_144]
33     at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
34     at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
35     at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
36     at
37 org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.prep
38 areContext(TomcatEmbeddedServletContainerFactory.java:208) ~[spring-boot-
39 1.4.7.RELEASE.jar:1.4.7.RELEASE]
40     at
41 org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.
42 getEmbeddedServletContainer(TomcatEmbeddedServletContainerFactory.java:176) ~[spring-boot-
43 1.4.7.RELEASE.jar:1.4.7.RELEASE]
44     at
45 org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.
46 createEmbeddedServletContainer(EmbeddedWebApplicationContext.java:164) ~[spring-boot-
47 1.4.7.RELEASE.jar:1.4.7.RELEASE]
48     at
49 org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh
50 (EmbeddedWebApplicationContext.java:134) ~[spring-boot-1.4.7.RELEASE.jar:1.4.7.RELEASE]
51     ... 8 common frames omitted
52 Caused by: java.lang.ClassNotFoundException: org.apache.juli.WebappProperties
53     at java.net.URLClassLoader.findClass(Unknown Source) ~[na:1.8.0_144]
54     at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
55     at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
56     at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_144]
57     ... 24 common frames omitted

二、错误分析：

由于我的 Eclipse 绑定的 Server 是 apache-tomcat-8.5.23，而引入的依赖 tomcat-juli-7.0.27.jar 版本过低，找不到类 org.apache.juli.WebappProperties

三、解决办法：

将 tomcat-juli-8.5.2.jar 版本的依赖加入pom文件，运行工程，至此 Console 控制台打印日志正常，问题解决。