值栈中的缺省值是什么? (使用#foo访问)
attr (按照顺序扫描request, session和application属性)
request (request attributes)
session (session attributes)
application (application attributes)
parameters (request params)

Note: WebWork from the CVS does not compile with the latest 1.5 J2sdk. Use the stable J2sdk 1.4.2.

Once you have built the xwork.jar copy it into the webwork/lib/core folder, and delete the old one.

<validators>
    <field name="name">
        <field-validator type="requiredstring">
            <message key="template.name.errors.required">A default message in case the key is not found</message>
        </field-validator>
    </field>
</validators>

How do I set a global resource bundle?

webwork.custom.i18n.resources=global-messages

Java class (thanks Drew McAuliffe):

public class WebworkGlobalMessagesListener implements ServletContextListener {
    private static Logger log = Logger.getLogger(WebworkGlobalMessagesListener.class);
    private static final String DEFAULT_RESOURCE = "global-messages";

    /**
     * Uses the LocalizedTextUtil to load messages from the global
     message bundle.
     * @see
     javax.servlet.ServletContextListener#contextInitialized(javax.servlet.Servle
     tContextEvent)
     */
    public void contextInitialized(ServletContextEvent arg0) {
        log.info("Loading global messages from " + DEFAULT_RESOURCE);
        LocalizedTextUtil.addDefaultResourceBundle(DEFAULT_RESOURCE);
        log.info("Global messages loaded.");
    }

    /**
     * @see javax.servlet.ServletContextListener#contextDestroyed(javax.servlet.ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent arg0) {

        // do nothing
    }

}

<listener>
<listener-class>mypackagename.WebworkGlobalMessagesListener</listener-class>
</listener>

How do I get access to the Session?
ActionContext.getContext().getSession() (returns Map, works internally using a ThreadLocal)

How can I get the HttpServletRequest?
ServletActionContext.getRequest() (works internally using a ThreadLocal)

How do I decouple XWork LocalizedTextUtil global resource bundle loading from serlvets (ServletContextListener)?
If you're using XWork outside a Web context, then use whatever startup hooks you have in that context (i.e. application start for a desktop app) to add the global resource bundle. This is a startup activity, so use whatever mechanisms are provided in the context you're running in.

#tag(Select "label='xxx '" "name='xxx'" "list=?")
or 
#tag(combobox "label='Prioridade'" "name='inavis.avisTpPrioridade'" "list=?")

html tag i use to do:

<select..>
  <otpion value="" selected>XXX</option>
</selct>

How do I add I18N to a UI tag, like ww:textfield?

<ww:textfield label="'i18n.label'" name="'label1'" value="''">

<ww:textfield label="getText('i18n.label')" name="'label1'" value="''">

Can I add I18N outside the Action's context? i.e. adding i18n to some JSP using the ww taglib?
Yes, use the <ww:i18n> tag to push a resource bundle on to the stack. Now calls with <ww:text/> or <ww:property value="getText(...)"/> will read from that resource bundle.

<xwork>
    <include file="webwork-default.xml"/>
    <include file="config-browser.xml"/>
    <package name="default" extends="webwork-default">
....
    </package>
    <include file="other.xml"/>
</xwork>

This tells it to load the webwork-default.xml from the webwork jar file
to get all of those interceptor and result definitions.

How can I put a String literal in a Javascript call, for instance in an onChange attribute?

onchange='"someFunc(this.form, \'abc\')"'

Notice here that there are single quotes surrounding the double quotes, and then the single quotes inline in the Javascript are escaped. This produces this result:

onchange="someFunc(this.form, 'abc')"

Why won't the 'if' tag evaluate a one char string?

<ww:if test="#myObj.myString == 'A'">
Why doesn't this work when myString is equal to A?
</ww:if>

<ww:if test='#myObj.myString == "A"'>
This works!
</ww:if>

Alternatively, you can escape the double quotes in the String:

<ww:if test="#myObj.myString == \"A\"">
This works!
</ww:if>

I'm trying to run the webwork example in the tutorial on Tomcat, and it can't instantiate the VelocityEngine

javax.servlet.ServletException: Servlet.init() for servlet webwork threw exception at
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:963)
…
root cause

Solution: (thanks to Keith Lea)

So that it's on file somewhere for other people, I will describe the solution:

runtime.log.logsystem.class=org.apache.velocity.runtime.log.NullLogSystem