Question

使用NullPointerException拦截器和execAndWait方法时，我得到validate()。在index.jsp中，textfield有一个firstName。当我提交时，它首先validate使用validate方法在Action类中的字符串execute。然后转到NullPointerException方法。在输出中，我在firstName方法中找不到validate字段execAndWait。在某个地方我开始知道，index.jsp在单独的线程中运行，这就是为什么会出现这个问题的原因。我想知道如何解决这个问题。文件明智的代码如下：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <%@ taglib uri="/struts-tags" prefix="s"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body> <s:actionerror /> <s:actionmessage /> <s:form action="go" method="post"> <s:textfield name="fname" label="First-Name" /> <s:submit value="enter"></s:submit> </s:form> </body> </html>

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="abc" extends="struts-default"> <interceptors> <interceptor-stack name="myStack"> <interceptor-ref name="defaultStack"></interceptor-ref> <interceptor-ref name="execAndWait"></interceptor-ref> </interceptor-stack> </interceptors> <action name="go" class="pack.GoAction"> <interceptor-ref name="myStack" /> <result name="success">/success.jsp</result> <result name="failure">/failure.jsp</result> <result name="input">/index.jsp</result> <result name="wait">/wait.jsp</result> </action> </package> </struts>

GoAction.java

package pack; import java.sql.*; import com.opensymphony.xwork2.ActionSupport; import com.opensymphony.xwork2.ModelDriven; public class GoAction extends ActionSupport implements ModelDriven<User> { private static final long serialVersionUID = 1L; private User user; public User getUser() { return user; } public void setUser(User user) { this.user = user; } @Override public User getModel() { System.out.println("****inside getModel()****"); user=new User(); return user; } public void validate(){ System.out.println("****inside validate****"); if(user.getFname().length()<4){ this.addFieldError("fname", "first name can not be less than 5"); System.out.println("console: first name can not be less than 5 "+user.getFname()); } if(user.getFname().length()==0){ this.addFieldError("fname", "first name found empty"); } } public String execute(){ System.out.println("****inside execute****"); String returnValue=""; int i=0; Connection con=null; ResultSet rs=null; PreparedStatement ps=null; if(user.getFname().equals("zebra")){ System.out.println("First-Name : zebra : not allowed."); this.addActionMessage("First-Name : zebra : not allowed"); return "failure"; } try{ Class.forName("oracle.jdbc.driver.OracleDriver"); con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe", "hibernate", "hibernate"); ps=con.prepareStatement("insert into table1 values(?)"); ps.setString(1, user.getFname()); i=ps.executeUpdate(); if(i!=0){ returnValue="success"; this.addActionMessage("data successfully inserted"); System.out.println("ok"); } else{ returnValue="failure"; System.out.println("not ok"); } }catch(Exception ex){ System.out.println("E x c e p t i o n o c c u r r e d !!!!"); ex.printStackTrace(); } return returnValue; } }

wait.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <%@ taglib uri="/struts-tags" prefix="s"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Wait...</title> <meta http-equiv="refresh" content="1;"> </head> <body> <img src="images/animation_processing.gif" /> </body> </html>

success.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <%@ taglib uri="/struts-tags" prefix="s"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body> Success !! <br> <s:actionmessage /> </body> </html>

****inside getModel()****
****inside validate****
****inside execute****
Apr 26, 2015 4:30:48 PM org.apache.struts2.util.TokenHelper warn
WARNING: Could not find token mapped to token name token
ok
****inside getModel()****
****inside validate****
Apr 26, 2015 4:30:50 PM org.apache.struts2.dispatcher.Dispatcher error
SEVERE: Exception occurred during processing request: null
java.lang.NullPointerException
    at pack.GoAction.validate(GoAction.java:35)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doBeforeInvocation(ValidationInterceptor.java:251)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263)
    at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:239)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:239)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:252)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:161)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:563)
    at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

OUTPUT-Screens（逐步） enter image description here

enter image description here

但是在数据库中插入了值： enter image description here

控制台OUTPUT

execAndWait

经过一段时间的浏览，我发现user.getFname()在一个单独的线程中运行，并且无法获得$(function() { // your code here });的值。任何人都可以帮我解决这个问题。

Answer 1

更改验证方法的逻辑

public void validate(){
    System.out.println("****inside validate****");
    if(user.getFname() == null || user.getFname().length()==0){
        this.addFieldError("fname", "first name found empty");
    } else
    if(user.getFname().length()<4){
        this.addFieldError("fname", "first name can not be less than 5");
        System.out.println("console: first name can not be less than 5 "+user.getFname());
    }
}

Answer 2

解决方案在于internalNode拦截器的工作方式以及struts2框架调用方法（private class internalNode implements Node<T> { // ^remove `<T>` from here，然后是execAndWait然后getModel()）的方式。另请注意，validate()在不同的主题中运行。您不能使用ActionContext，因为它是ThreadLocal。这意味着如果您需要访问例如会话数据，则需要实现SessionAware而不是调用ActionContext.getSession（）。

---- execAndWait如何工作------

由@Roman C和API Docs

讲述

execute在超时后返回等待结果，一次又一次地调用您的操作，直到执行操作为止。如果它没有参数，则不会将其设置为操作，验证始终会失败。

由于execAndWait拦截器在每1秒间隔后重复调用execAndWait（以及NullPointerException）这一事实，上述程序正在抛出execAndWait（参见wait.jsp getModel()）。

因此，当它再次调用validate()时，它会设置原始<meta http-equiv="refresh" content="1;"/>对象，即没有任何参数getModel()。因此，在new User();之后，它再次进入fname。这次它发现getModel()为validate()。因此，要解决上述问题，只需使用以下代码替换fname类：

<强> GoAction

null

在这段代码中，我正在GoAction方法中检查package pack; import java.sql.*; import java.util.Map; import org.apache.struts2.dispatcher.SessionMap; import org.apache.struts2.interceptor.SessionAware; import com.opensymphony.xwork2.ActionSupport; import com.opensymphony.xwork2.ModelDriven; public class GoAction extends ActionSupport implements ModelDriven<User>,SessionAware { private SessionMap<String, Object> sm; private static final long serialVersionUID = 1L; private User user; public User getUser() { return user; } public void setUser(User user) { this.user = user; } @Override public User getModel() { System.out.println("****inside getModel()****"); User u=(User) sm.get("user"); if(u==null){ user=new User(); } else{ user=u; } return user; } public void validate(){ sm.put("user", user); User u=(User) sm.get("user"); System.out.println("^^^"+u.getFname()); System.out.println("****inside validate****"); if(u.getFname().length()<4){ this.addFieldError("fname", "first name can not be less than 5"); System.out.println("console: first name can not be less than 5 "+user.getFname()); } } public String execute() throws InterruptedException{ System.out.println("****inside execute****"); String returnValue=""; int i=0; Connection con=null; ResultSet rs=null; PreparedStatement ps=null; if(user.getFname().equals("zebra")){ System.out.println("First-Name : zebra : not allowed."); this.addActionMessage("First-Name : zebra : not allowed"); return "failure"; } try{ Class.forName("oracle.jdbc.driver.OracleDriver"); con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe", "hibernate", "hibernate"); ps=con.prepareStatement("insert into table1 values(?)"); ps.setString(1, user.getFname()); i=ps.executeUpdate(); if(i!=0){ returnValue="success"; this.addActionMessage("data successfully inserted"); System.out.println("ok"); } else{ returnValue="failure"; System.out.println("not ok"); } }catch(Exception ex){ System.out.println("E x c e p t i o n o c c u r r e d !!!!"); ex.printStackTrace(); } return returnValue; } @Override public void setSession(Map<String, Object> sm) { this.sm=(SessionMap<String, Object>) sm; } }对象存储的会话映射。如果未找到：user。如果找到：返回它。

execAndWait拦截器无法使用验证

2 个答案: