解决了，return SUCCESS;相当于return “success”;

struts.xml改成<result name="success">/index.jsp</result>

HelloAction.java

package action;

import com.opensymphony.xwork2.ActionSupport;

public class HelloAction extends ActionSupport {

/**

* 

*/

private static final long serialVersionUID = 1L;

@Override

public String execute() throws Exception {

System.out.println("执行Action");

return SUCCESS;

}

}

struts.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE struts PUBLIC

"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"

"http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>

<package name="default" namespace="/" extends="struts-default">

<action name="HH" class="action.HelloAction">

<result>/index.jsp</result>

</action>

</package>

</struts>