Java-ClassNotFoundException之异常解决

错误异常

ERROR com.mdd.documentary.exception.GlobalExceptionHandler - org.springframework.web.util.NestedServletException: Handler dispatch failed; nested exception is java.lang.NoClassDefFoundError: org/apache/http/entity/mime/MultipartEntityBuilder
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1055)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
        at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at com.github.xiaoymin.knife4j.spring.filter.ProductionSecurityFilter.doFilter(ProductionSecurityFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at com.github.xiaoymin.knife4j.spring.filter.SecurityBasicAuthFilter.doFilter(SecurityBasicAuthFilter.java:90)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.

首先，先了解一下java.lang.ClassNotFoundException。NoClassDefFoundError错误的发生，是因为Java虚拟机在编译时能找到合适的类，而在运行时不能找到合适的类导致的错误。例如在运行时我们想调用某个类的方法或者访问这个类的静态成员的时候，发现这个类不可用，此时Java虚拟机就会抛出NoClassDefFoundError错误。与ClassNotFoundException的不同在于，这个错误发生只在运行时需要加载对应的类不成功，而不是编译时发生。很多Java开发者很容易在这里把这两个错误搞混。

错误原因：

了解了java.lang.ClassNotFoundException错误的原因，就大致了解此问题大致所在了，就是缺少了 httpmime.jar这个包。

问题解决：

Maven增加如下依赖

  org.apache.httpcomponents
  httpmime
  4.3.2

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