public class ValidateForm extends ActionForm {
    
    private User user = new User();
    
    public User getUser() {
        return user;
    }
    
    public void setUser(User user) {
        this.user = user;
    }

    @Override
    public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) {
        ActionErrors errors = new ActionErrors();
        if(user.getName() == null || "".equals(user.getName().trim())) {
            System.out.println("name must be not null!");
            errors.add("name", new ActionMessage("name", "name must be not null!"));
        }
        if(errors.get().hasNext()) {
            System.out.println("here is ValidateForm and has errors");
            return errors;
        } else {
            System.out.println("here is ValidateForm and no errors");
            return null;
        }
    }


}

Action的execute方法只有一句mapping.findForward("success");

<struts-config>

    <form-beans>
        <form-bean name="validateForm"
            type="com.struts.form.ValidateForm">
        </form-bean>
    </form-beans>

    <action-mappings>
        <!-- 带有验证功能的ACTION -->
        <action path="/validateAction" name="validateForm"
            type="com.struts.action.ValidateAction"
            input="/ValidateAction/errors.jsp" validate="true">
            <forward name="success" path="/WEB-INF/user/success.jsp"></forward>
        </action>
    </action-mappings>
    <message-resources parameter="MessageResources" />
</struts-config>

name must be not null!
here is ValidateForm and has errors
//上面这两句是System.out.println输出的
2011-4-27 21:32:02 org.apache.struts.util.PropertyMessageResources loadLocale
警告:   Resource MessageResources_zh_CN.properties Not Found.
2011-4-27 21:32:02 org.apache.struts.util.PropertyMessageResources loadLocale
警告:   Resource MessageResources_zh.properties Not Found.
2011-4-27 21:32:02 org.apache.struts.util.PropertyMessageResources loadLocale
警告:   Resource MessageResources.properties Not Found.