为什么 execAndWait 拦截器不能与验证一起使用？

问题描述 投票：0回答：2

使用带有 

NullPointerException
方法的 
execAndWait
拦截器时，我得到 
validate()
。

在 

index.jsp
中，我有一个 
textfield
代表 
firstName
。当我提交时，它首先使用 
Action
方法验证 
validate()
类中的字符串，然后转到 
execute()
方法。

在输出中，我在 

NullPointerException
方法中找不到 
firstName
字段，得到 
validate()
。我在某个地方知道，
execAndWait
在单独的线程中运行，这就是出现这个问题的原因。我想知道如何解决这个问题。

下面的文件明智代码：

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
:

<?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>

输出屏幕（逐步）：

enter image description here

enter image description here

enter image description here

但是值已插入数据库中： enter image description here

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)

经过一番浏览，我发现

execAndWait
运行在一个单独的线程中，并且无法能够获取
user.getFname()
的值。谁能帮我解决这个问题吗？

java validation jsp struts2
2个回答
1
投票

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());
    }
}
0
投票

解决方案在于

execAndWait
拦截器的工作方式以及struts2框架调用方法的方式（
getModel()
，然后
validate()
，然后
execute
）。另请注意，
execAndWait
在不同的线程中运行。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，您需要实现 SessionAware 而不是调用 ActionContext.getSession()。

----execAndWait 是如何工作的-----

正如 @Roman C 以及 API 文档中所述

  • execAndWait
    在超时后返回等待结果，以便一次又一次地调用您的操作，直到执行该操作。如果它没有参数，它们将不会被设置为操作，并且验证总是失败。

上面的程序抛出 

NullPointerException
，因为 
execAndWait
拦截器在每 1 秒间隔后重复调用 
getModel()
（以及 
validate()
）（参见 wait.jsp 
<meta http-equiv="refresh" content="1;"/>
）。

因此，当它再次调用 

getModel()
时，它正在设置原始 
new User();
对象，即没有任何参数 
fname
。所以，在
getModel()
之后，又进入
validate()
。这次它发现 
fname
是 
null
。因此，要解决上述问题，只需用以下代码替换 
GoAction
类：

开始行动

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;
    }
}

在此代码中，我正在检查 

user
方法中存储的 
getModel()
对象存储的会话映射。如果没有找到：
new User()
。如果找到：退回。

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