刚刚模仿孙卫琴的struts做的login 发现返回显示错误信息老是有强制类型转换异常

Question

将里面的
errors.add("userid", new ActionMessage("userlogin.no.userid.error"));
改成：
errors.add("userid",new ActionError("userlogin.no.userid.error"));试试看，我是这样写的

Answer 1

ActionErrors errors = new ActionErrors();
声明的errors是ActionErrors,
当然是用
errors.add("userid",new ActionError("userlogin.no.userid.error"));

Answer 2

errors.add("userid",new ActionError("userlogin.no.userid.error"));

Answer 3

楼主:
我这里一切正常，没有异常出现UserloginForm.java
------------------------------------
package login;import javax.servlet.http.HttpServletRequest;
import org.apache.struts.action.ActionMessage;
import org.apache.struts.action.ActionErrors;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionMapping;
public final class UserloginForm extends ActionForm { private String userId = null;
private String userPassword = null; public String getUserId() { return (this.userId); }
    public void setUserId(String userid) { this.userId = userid; } public String getUserPassword() { return (this.userPassword); }
public void setUserPassword(String userPassword){ this.userPassword = userPassword; }
public void reset(ActionMapping mapping, HttpServletRequest request){
this.userId = null;
this.userPassword = null;
}
//.................
public ActionErrors validate(ActionMapping mapping,
            HttpServletRequest request) {
        ActionErrors errors = new ActionErrors();        if ((userId == null) || (userId.length() < 6)) {//用户名为空或者小于6就返回错误信息
            errors.add("userid", new ActionMessage(
                            "userlogin.no.userid.error"));
        }
        if ((userPassword == null) || (userPassword.length() < 6)) {//密码为空或者小于6就返回错误信息
            errors.add("userpassword",new ActionMessage("userlogin.no.userpassword.error"));
        }        return errors;//errors为空表示没有错误，继续下面的流程    }//...................
}------------------------------------UserloginAction.java
------------------------------------
package login;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;public final class UserloginAction extends Action {
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception { return(mapping.findForward("Success"));
}
}
------------------------------------
web.xml
------------------------------------
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" 
 "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd"><web-app>
<display-name>CSdn Login Application</display-name> <!-- Standard Action Servlet Configuration -->
<servlet>
<servlet-name>action</servlet-name>
<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/struts-config.xml</param-value>
</init-param>
<load-on-startup>2</load-on-startup>
</servlet> <!-- Standard Action Servlet Mapping -->
<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping> <!-- The Usual Welcome File List -->
<welcome-file-list>
<welcome-file>login.jsp</welcome-file>
</welcome-file-list> <!-- Struts Tag Library Descriptors -->
<taglib>
<taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-bean.tld</taglib-location>
</taglib> <taglib>
<taglib-uri>/WEB-INF/struts-html.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-html.tld</taglib-location>
</taglib></web-app>
------------------------------------struts-config.xml
------------------------------------
<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 1.1//EN"
   "http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd"><struts-config> <!-- ============ Form Bean Definitions ================================= -->
<form-beans>
<form-bean name="LoginForm" type="login.UserloginForm"/>

</form-beans> <!-- ============ Action Mapping Definitions ============================ -->
<action-mappings>
<!-- Say Hello! -->
<action path = "/userlogin"
type = "login.UserloginAction"
name = "LoginForm"
scope = "request"
validate= "true"
input = "/login.jsp"
>
<forward name="Success" path="/success.jsp"/>
</action>
</action-mappings> <!-- ============ Message Resources Definitions ========================= -->
<message-resources parameter="login.ApplicationResources"/></struts-config>
------------------------------------success.jsp
------------------------------------
Success!!!!!!!
------------------------------------其他的和楼主的相同