struts 2.3 升级到 2.5.30后过滤器超时报错：
Connection timed out: connect - [unknown location]
com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:120)
com.opensymphony.xwork2.validator.DefaultValidatorFileParser.parseActionValidatorConfigs(DefaultValidatorFileParser.java:84)
com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.loadFile(AnnotationActionValidatorManager.java:380)
com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.buildClassValidatorConfigs(AnnotationActionValidatorManager.java:269)
com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.buildValidatorConfigs(AnnotationActionValidatorManager.java:361)
com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.getValidators(AnnotationActionValidatorManager.java:97)
com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.validate(AnnotationActionValidatorManager.java:136)
com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.validate(AnnotationActionValidatorManager.java:128)
com.opensymphony.xwork2.validator.AnnotationActionValidatorManager.validate(AnnotationActionValidatorManager.java:123)

• 问题原因：validation.xml文件头需要修改

    <!DOCTYPE validators PUBLIC "-//OpenSymphony Group//XWork Validator 1.0.2//EN" 
        "http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd">

  变更为：

    <!DOCTYPE validators PUBLIC "-//Apache Struts//XWork Validator 1.0.2//EN"
     "http://struts.apache.org/dtds/xwork-validator-1.0.2.dtd">