• 拋錯

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [com/mico/domo/springboot/demo/config/DruidDBConfig.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [javax.sql.DataSource]: Factory method 'dataSource' threw exception; nested exception is java.lang.NoClassDefFoundError: org/apache/log4j/Logger
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:627)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:456)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1288)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1127)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:538)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:498)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1244)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1164)
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:857)
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:760)
    ... 28 common frames omitted
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [javax.sql.DataSource]: Factory method 'dataSource' threw exception; nested exception is java.lang.NoClassDefFoundError: org/apache/log4j/Logger
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:622)
    ... 42 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/Logger
    at com.alibaba.druid.filter.logging.Log4jFilter.<init>(Log4jFilter.java:26)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at java.lang.Class.newInstance(Class.java:442)
    at com.alibaba.druid.filter.FilterManager.loadFilter(FilterManager.java:114)
    at com.alibaba.druid.pool.DruidAbstractDataSource.addFilters(DruidAbstractDataSource.java:1230)
    at com.alibaba.druid.pool.DruidAbstractDataSource.setFilters(DruidAbstractDataSource.java:1219)
    at com.mico.domo.springboot.demo.config.DruidDBConfig.dataSource(DruidDBConfig.java:102)
    at com.mico.domo.springboot.demo.config.DruidDBConfig$$EnhancerBySpringCGLIB$$b8f4ceda.CGLIB$dataSource$0(<generated>)
    at com.mico.domo.springboot.demo.config.DruidDBConfig$$EnhancerBySpringCGLIB$$b8f4ceda$$FastClassBySpringCGLIB$$caae8b62.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:363)
    at com.mico.domo.springboot.demo.config.DruidDBConfig$$EnhancerBySpringCGLIB$$b8f4ceda.dataSource(<generated>)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
    ... 43 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Logger
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 63 common frames omitted

• 可以通過添加

<dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
</dependency>

• 但是這樣導(dǎo)致的問題是SpringBoot和Druid分別用自己的日志框架没佑，SpringBoot用的是slf4j和logback搀庶。druid使用的日志框架是log4j,個人比較推薦的做法：引入log4j-over-slf4j包，作用是通過中間包來替換log4j日志框架即彪，所有日志最終都統(tǒng)一到slf4j友酱，并由logback實現(xiàn)兼丰。

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>log4j-over-slf4j</artifactId>
            <version>1.7.25</version>
        </dependency>
  

• log4j-over-slf4j:
  To use log4j-over-slf4j in your own application, the first step is to locate and then to replace log4j.jar with log4j-over-slf4j.jar. Note that you still need an SLF4J binding and its dependencies for log4j-over-slf4j to work properly.

  In most situations, replacing a jar file is all it takes in order to migrate from log4j to SLF4J.

  Note that as a result of this migration, log4j configuration files will no longer be picked up. If you need to migrate your log4j.properties file to logback, the log4j translator (用這個可以將log4j的配置文件轉(zhuǎn)換成logback的配置文件)might be of help. For configuring logback, please refer to its manual.

• 附贈一個logback配置文件(logback.xml)

<?xml version="1.0" encoding="UTF-8"?>

<configuration>
    <appender name="FILE" class="ch.qos.logback.core.FileAppender">
        <file>/data/www/file/logs/springboot.log</file>

        <encoder>
            <pattern>%date %level [%thread] %logger{10} [%file:%line] %msg%n</pattern>
        </encoder>
    </appender>

    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
        <pattern>%msg%n</pattern>
    </encoder>
    </appender>

    <root level="debug">
        <appender-ref ref="FILE" />
        <appender-ref ref="STDOUT" />
    </root>
</configuration>