1、需要升级的jar包，替换目前对应的老的jar包。所需jar包直接sturts2官网下载
2、升级jar包后需要修改的文件web.xml
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
红色代码替换成org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter
3、升级后struts2配置文件修改
2.1换成2.5
另外struts2升级后统配符问题：
<action name="a*" method="{1}" class="aAction">
<result name="b">
/b.jsp
</result>
<allowed-methods>c,d</allowed-methods>
</action>
统配符使用修改的关键：添加allowed-methods，把aAction中统配的对应的方法列出来。多个方法之前用逗号隔开。
4、升级后使用的的log4j的包是2.7，原来使用的Logger也无法使用需要重新导包。（如果你以前就使用的log4j 2，则无需担心），需要调整的同学这里给一个使用的例子，本例子是properties文件配置的
注意：log4j.properties需要修改为log4j2.properties
#OFF、FATAL、ERROR、WARN、INFO、DEBUG、ALL
status = error
name = PropertiesConfig
filters = threshold
filter.threshold.type = ThresholdFilter
filter.threshold.level = info
rootLogger.level = info
#定义输出：I，info，E，error
rootLogger.appenders =I,E
rootLogger.appenderRef.I.ref = InfoRollingFile
rootLogger.appenderRef.I.level = info
rootLogger.appenderRef.I.additivity = true
rootLogger.appenderRef.E.ref = ErrorRollingFile
rootLogger.appenderRef.E.level = error
rootLogger.appenderRef.E.additivity = true
appender.I.type = RollingFile
appender.I.name = InfoRollingFile
appender.I.fileName = /a/b/c/d.log
appender.I.filePattern = /a/b/c/d-%d{yyyyMMdd}-%i.log
appender.I.layout.type = PatternLayout
appender.I.layout.pattern = %d %p %C{1.} [%t] %m%n
appender.I.policies.type = Policies
appender.I.policies.time.type = TimeBasedTriggeringPolicy
appender.I.policies.time.interval = 2
appender.I.policies.time.modulate = false
appender.I.policies.size.type = SizeBasedTriggeringPolicy
appender.I.policies.size.size = 100MB
appender.I.strategy.type = DefaultRolloverStrategy
appender.I.strategy.max = 5
appender.E.type = RollingFile
appender.E.name = ErrorRollingFile
appender.E.fileName = /a/b/c/d.log
appender.E.filePattern = /a/b/c/d_error-%d{yyyyMMdd}-%i.log
appender.E.layout.type = PatternLayout
appender.E.layout.pattern = %d %p %C{1.} [%t] %m%n
appender.E.policies.type = Policies
appender.E.policies.time.type = TimeBasedTriggeringPolicy
appender.E.policies.time.interval = 2
appender.E.policies.time.modulate = false
appender.E.policies.size.type = SizeBasedTriggeringPolicy
appender.E.policies.size.size = 100MB
appender.E.strategy.type = DefaultRolloverStrategy
appender.E.strategy.max = 5
到此升级完成。