报错原因：
org.springframework.web.util.NestedServletException: Handler dispatch failed; nested exception is java.lang.NoClassDefFoundError: com/alibaba/fastjson/JSON
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1054)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897)
javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
解决办法 ：
没有打包导致:
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