改造tomcat来 获取默认的路径

  <Context docBase="E:\eclipse\apache-tomcat-8.5.35\wtpwebapps\day16_5" path="/day16_5" reloadable="true" source="org.eclipse.jst.jee.server:day16_5"/></Host>
      <!--  -->
	  <Context docBase = "o2o" path = /o2o reloadable = "true" source = "org.eclipse.jst.jee.server:o2o"/>
	   <!--  只要请求路径中包含有path = "/upload" ：path 时候就会自动解析为/User/ddd/upload  再拼接数据库中查询到的路径-->
	  <Context docBase = "/User/ddd/upload" path = "/upload"/>
	  </Host>