NoClassDefFoundError: javax/servlet/http/HttpServletResponse异常解决方法

向右看齐 2022-02-14 00:08 570阅读 0赞

场景描述：  
maven+springboot项目，启动的时候出现异常，具体信息如下：

Caused by: java.lang.NoClassDefFoundError: javax/servlet/http/HttpServletRequest
    	at java.lang.Class.getDeclaredMethods0(Native Method) ~[na:1.8.0_181]
    	at java.lang.Class.privateGetDeclaredMethods(Class.java:2701) ~[na:1.8.0_181]
    	at java.lang.Class.getDeclaredMethods(Class.java:1975) ~[na:1.8.0_181]
    	at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:613) ~[spring-core-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    	at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:524) ~[spring-core-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    	at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:510) ~[spring-core-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:247) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    	... 17 common frames omitted
    Caused by: java.lang.ClassNotFoundException: javax.servlet.http.HttpServletRequest
    	at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_181]
    	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_181]
    	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[na:1.8.0_181]
    	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_181]
    	... 24 common frames omitted

NoClassDefFoundError和ClassNotFoundException一般是运行时Class未加载到时出现的异常

<table> 
 <thead> 
  <tr> 
   <th align="center">ClassNotFoundException 1</th> 
   <th align="right">NoClassDefFoundError 2</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">从java.lang.Exception继承，是一个Exception类型</td> 
   <td align="right">从java.lang.Error继承，是一个Error类型</td> 
  </tr> 
  <tr> 
   <td align="center">当动态加载Class的时候找不到类会抛出该异常</td> 
   <td align="right">当编译成功以后执行过程中Class找不到导致抛出该错误</td> 
  </tr> 
  <tr> 
   <td align="center">一般在执行Class.forName()、ClassLoader.loadClass()或ClassLoader.findSystemClass()的时候抛出</td> 
   <td align="right">由JVM的运行时系统抛出</td> 
  </tr> 
 </tbody> 
</table>

那么一定是运行时没有加载到servlet-api.jar，由于是web项目用的tomcat部署，一般都是tomcat中；检查maven配置

<groupId>com.geekq</groupId>
    <artifactId>miaosha</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
        ...
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
         <exclusions>
             <exclusion>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-starter-tomcat</artifactId>
             </exclusion>
             <exclusion>
                 <groupId>org.slf4j</groupId>
                 <artifactId>slf4j-log4j12</artifactId>
             </exclusion>
             <exclusion>
                 <groupId>log4j</groupId>
                 <artifactId>log4j</artifactId>
             </exclusion>
         </exclusions>
     </dependency>
     ...
     <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        
        <scope>provided</scope>
    </dependency>

这里把内置的tomcat生命周期配置成provided，造成运行时找不到class，调整后：

<dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
         <exclusions>
             <exclusion>
                 <groupId>org.slf4j</groupId>
                 <artifactId>slf4j-log4j12</artifactId>
             </exclusion>
             <exclusion>
                 <groupId>log4j</groupId>
                 <artifactId>log4j</artifactId>
             </exclusion>
         </exclusions>
     </dependency>