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execAndWait拦截器不适用于验证

本文介绍了execAndWait拦截器不适用于验证的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

当将execAndWait拦截器与validate()方法一起使用时，我得到了NullPointerException.在index.jsp中，我有一个textfield用于firstName.当我提交时，它首先使用validate方法在Action类中的那个字符串validate.然后转到execute方法.在输出中，对于validate方法中找不到的firstName字段，我得到的是NullPointerException.我知道的某个地方，execAndWait在单独的线程中运行，这就是为什么出现此问题的原因.我想知道如何解决这个问题.明智的文件代码如下:

I am getting NullPointerException when using execAndWait interceptor with validate() method. In index.jsp, I have one textfield for firstName. When I do submit, it first validate that string in Action class with validate method. Then it goes to execute method. In output I am getting NullPointerException for firstName field not found in validate method. Somewhere I came to know that, execAndWait runs in separate thread, that's why this problem arises. I want to know how to resolve this problem. File wise code below:

index.jsp:

index.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>
    <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:

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:

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:

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:

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>

输出屏幕(逐步)

但是在数据库中插入了值:

however value got inserted in Database:

控制台输出 

****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)

经过一些浏览，我知道execAndWait在单独的线程中运行，并且无法获取user.getFname()的值.谁能帮我解决这个问题.

After a bit of browsing, I came to know that execAndWait runs in a separate thread and is NOT able to get the value of user.getFname(). Can anyone help me resolving this issue.

推荐答案

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());
    }
}

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09-16 23:26
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