整理asyncweb代码的时候，收到如下异常信息：

ArtifactDescriptorException: Failed to read artifact descriptor for org.springframework:spring-dao:jar:2.0.8: ArtifactResolutionException: Failure to transfer org.springframework:spring-dao:pom:2.0.8 from http://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact org.springframework:spring-dao:pom:2.0.8 from/to central (http://repo.maven.apache.org/maven2): null to http://repo.maven.apache.org/maven2/org/springframework/spring-dao/2.0.8/spring-dao-2.0.8.pom

检查了一下发现是spring的版本过低，在maven库中检索不到，索性换成3.2.4，问题解决。