Spring 无法访问Servlet中的Java Bean，getAttribute（）返回null_Spring_Jsp_Tomcat_Servlets_Javabeans

Spring 无法访问Servlet中的Java Bean，getAttribute（）返回null

spring jsp tomcat servlets

Spring 无法访问Servlet中的Java Bean，getAttribute（）返回null,spring,jsp,tomcat,servlets,javabeans,Spring,Jsp,Tomcat,Servlets,Javabeans,我不熟悉在servlet中使用Javabean，从HttpServletRequest对象访问bean时遇到问题。当我使用getAttribute（）时，它返回null。这是我的密码： Station.jsp-jsp： <!-- @author - Dylan Stout 7/19/2016 Description: Station Screen -- Takes scanner input to three fields: fromStation, toSt

我不熟悉在servlet中使用Javabean，从HttpServletRequest对象访问bean时遇到问题。当我使用getAttribute（）时，它返回null。这是我的密码：

Station.jsp-jsp：

<!-- 
    @author - Dylan Stout 
    7/19/2016

    Description: Station Screen -- Takes scanner input to three fields: fromStation, toStation, toLoad
    Javascript is used to handle cursor position,incrementing fields, and button-press for load releasing. 
    PickProcess java bean holds the session information necessary to verify and send/recieve messages to wrxj 
    back-end. 

    Each input field is it's own form so no handling for carriage returns is needed (symbol guns usually
    send carriage return after scan) 

 -->
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<jsp:useBean id="pickProcess" class="com.wynright.scanui.model.PickProcess" scope="session"/>
<jsp:useBean id="fromStation" class="com.wynright.scanui.model.FromStation" scope="request"/>
<jsp:useBean id="toStation" class="com.wynright.scanui.model.ToStation" scope="request"/>
<jsp:useBean id="toLoad" class="com.wynright.scanui.model.ToLoad" scope="request"/>
<html>
<head>
<meta name="viewport" content="width=240, height=320, user-scalable=no,
initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0" />
<link type="text/css" rel="stylesheet" href="css/scanui.css">
<script type="text/javascript" src="scripts/jquery-3.1.0.min.js"></script>
<script type="text/javascript"  src="scripts/formController.js"></script>
<script type="text/javascript"  src="scripts/station.js"></script>
<noscript>JavaScript is off. Please enable to use ScanUI.</noscript>
<title>Station Pick - Scan UI</title>
</head>
<% 
if(fromStation.hasErrors()){ 
%>
<body OnLoad="onBodyLoad();focusFromStation();">
<% 
}else if(toStation.hasErrors()) { 
%>
<body OnLoad="onBodyLoad();focusToStation();">
<% 
}else if(toLoad.hasErrors()){ 
%>
<body OnLoad="onBodyLoad();focusToLoad();">
<% 
}else{ 
%>
<body OnLoad="onBodyLoad();focusNext();">
<% 
}
%>

<table cellpadding=4 cellspacing=2>
        <th bgcolor="#CCCCFF" colspan=2><font size=2>Station Pick</font></th>

        <tr bgcolor="#c8d8f8">
            <td valign=top><form name="fromStation" action="ValidateFromStation" method=post>
                    From Station: <input type="text" name="value"
                        value='<%=pickProcess.getFromStation()%>' size=5 maxlength=5 tabindex="1"> 
                        <br> 
                    <font size=2 color=red><%=fromStation.getErrorMsg("fromStation")%></font>

                </form></td>
            <td valign=top><form name="toStation" action="validateToStation.jsp" method=post>
                    To Station: <input type="text" name="value"
                        value='<%=pickProcess.getToStation()%>' size=5 maxlength=5 tabindex="2"> 
                        <br>
                    <font size=2 color=red><%=toStation.getErrorMsg("toStation")%></font>
                </form></td>
        </tr>
        <tr bgcolor="#c8d8f8">
            <td valign=top colspan="2"><form name="toLoad" action="validateToLoad.jsp" method=post>
                    To Load: <input type="text" name="value"
                        value='<%=pickProcess.getToLoad()%>' size=34 maxlength=30 tabindex="3"> 
                        <br>
                    <font size=2 color=red><%=toLoad.getErrorMsg("toLoad")%></font>
                </form></td>
        </tr>
    </table>



</body>
</html>

/**
 * 
 */
package com.wynright.scanui.action;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

import com.scanui.model.FromStation;

/**
 * @author dystout
 * Date: Jul 21, 2016
 *
 * Description: TODO
 */
public class ValidateFromStation extends HttpServlet{

    /**
     * 
     */
    private static final long serialVersionUID = 6201980136409592032L;

protected static Logger logger = Logger.getLogger(ValidateFromStation.class); 

protected FromStation fromStation = null; 

@Override
public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException,ServletException{

    fromStation = (FromStation)request.getSession(false).getAttribute("fromStation");           
    fromStation.setValue(request.getParameter("value"));
    if(fromStation.validate()){ 
        logger.debug("From Station Validated: " + fromStation.getValue());
        RequestDispatcher rd = request.getRequestDispatcher("Station.jsp"); 
        rd.include(request, response);
    }else{ 
        logger.debug("From Station INVALID, not validated: " + fromStation.getValue()); 
        RequestDispatcher rd = request.getRequestDispatcher("Station.jsp"); 
        rd.include(request,response); 
    }
}

}

package com.wynright.scanui.model;

import java.util.Hashtable;

import com.daifukuamerica.wrxj.application.Application;
import com.daifukuamerica.wrxj.application.PropertiesStack;
import com.daifukuamerica.wrxj.custom.piolax.dataserver.PiolaxPickServer;
import com.daifukuamerica.wrxj.jdbc.DBCommException;
import com.daifukuamerica.wrxj.jdbc.DBException;
import com.daifukuamerica.wrxj.jdbc.DBResultSet;

import com.wynright.scanui.connectionFactory.DBConnection;

public class FromStation extends ScanField{


    @Override
    public boolean validate(){ 

        if(value.equals("")){ 
            errors.put("fromStationNumber", "Please scan/enter valid station"); 
        }

        String sql = "SELECT SDESTINATIONSTATION FROM ORDERHEADER WHERE SDESTINATIONSTATION = '" + getValue() + "'"; 
        DBResultSet results = null; 

        if(DBConnection.getWrxjConnection().isConnectionActive()){ 
            try {
                 results= DBConnection.getWrxjConnection().execute(sql, null);
            } catch (DBCommException | DBException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
        }

        if(results != null && results.getRowCount()!=0){ 
            isValidated = true; 
        }

        //TODO -- Add WRXJ server validate (JSON)

        return isValidated; 
    }

}

FromStationjavabean：

<!-- 
    @author - Dylan Stout 
    7/19/2016

    Description: Station Screen -- Takes scanner input to three fields: fromStation, toStation, toLoad
    Javascript is used to handle cursor position,incrementing fields, and button-press for load releasing. 
    PickProcess java bean holds the session information necessary to verify and send/recieve messages to wrxj 
    back-end. 

    Each input field is it's own form so no handling for carriage returns is needed (symbol guns usually
    send carriage return after scan) 

 -->
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<jsp:useBean id="pickProcess" class="com.wynright.scanui.model.PickProcess" scope="session"/>
<jsp:useBean id="fromStation" class="com.wynright.scanui.model.FromStation" scope="request"/>
<jsp:useBean id="toStation" class="com.wynright.scanui.model.ToStation" scope="request"/>
<jsp:useBean id="toLoad" class="com.wynright.scanui.model.ToLoad" scope="request"/>
<html>
<head>
<meta name="viewport" content="width=240, height=320, user-scalable=no,
initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0" />
<link type="text/css" rel="stylesheet" href="css/scanui.css">
<script type="text/javascript" src="scripts/jquery-3.1.0.min.js"></script>
<script type="text/javascript"  src="scripts/formController.js"></script>
<script type="text/javascript"  src="scripts/station.js"></script>
<noscript>JavaScript is off. Please enable to use ScanUI.</noscript>
<title>Station Pick - Scan UI</title>
</head>
<% 
if(fromStation.hasErrors()){ 
%>
<body OnLoad="onBodyLoad();focusFromStation();">
<% 
}else if(toStation.hasErrors()) { 
%>
<body OnLoad="onBodyLoad();focusToStation();">
<% 
}else if(toLoad.hasErrors()){ 
%>
<body OnLoad="onBodyLoad();focusToLoad();">
<% 
}else{ 
%>
<body OnLoad="onBodyLoad();focusNext();">
<% 
}
%>

<table cellpadding=4 cellspacing=2>
        <th bgcolor="#CCCCFF" colspan=2><font size=2>Station Pick</font></th>

        <tr bgcolor="#c8d8f8">
            <td valign=top><form name="fromStation" action="ValidateFromStation" method=post>
                    From Station: <input type="text" name="value"
                        value='<%=pickProcess.getFromStation()%>' size=5 maxlength=5 tabindex="1"> 
                        <br> 
                    <font size=2 color=red><%=fromStation.getErrorMsg("fromStation")%></font>

                </form></td>
            <td valign=top><form name="toStation" action="validateToStation.jsp" method=post>
                    To Station: <input type="text" name="value"
                        value='<%=pickProcess.getToStation()%>' size=5 maxlength=5 tabindex="2"> 
                        <br>
                    <font size=2 color=red><%=toStation.getErrorMsg("toStation")%></font>
                </form></td>
        </tr>
        <tr bgcolor="#c8d8f8">
            <td valign=top colspan="2"><form name="toLoad" action="validateToLoad.jsp" method=post>
                    To Load: <input type="text" name="value"
                        value='<%=pickProcess.getToLoad()%>' size=34 maxlength=30 tabindex="3"> 
                        <br>
                    <font size=2 color=red><%=toLoad.getErrorMsg("toLoad")%></font>
                </form></td>
        </tr>
    </table>



</body>
</html>

/**
 * 
 */
package com.wynright.scanui.action;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

import com.scanui.model.FromStation;

/**
 * @author dystout
 * Date: Jul 21, 2016
 *
 * Description: TODO
 */
public class ValidateFromStation extends HttpServlet{

    /**
     * 
     */
    private static final long serialVersionUID = 6201980136409592032L;

protected static Logger logger = Logger.getLogger(ValidateFromStation.class); 

protected FromStation fromStation = null; 

@Override
public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException,ServletException{

    fromStation = (FromStation)request.getSession(false).getAttribute("fromStation");           
    fromStation.setValue(request.getParameter("value"));
    if(fromStation.validate()){ 
        logger.debug("From Station Validated: " + fromStation.getValue());
        RequestDispatcher rd = request.getRequestDispatcher("Station.jsp"); 
        rd.include(request, response);
    }else{ 
        logger.debug("From Station INVALID, not validated: " + fromStation.getValue()); 
        RequestDispatcher rd = request.getRequestDispatcher("Station.jsp"); 
        rd.include(request,response); 
    }
}

}

package com.wynright.scanui.model;

import java.util.Hashtable;

import com.daifukuamerica.wrxj.application.Application;
import com.daifukuamerica.wrxj.application.PropertiesStack;
import com.daifukuamerica.wrxj.custom.piolax.dataserver.PiolaxPickServer;
import com.daifukuamerica.wrxj.jdbc.DBCommException;
import com.daifukuamerica.wrxj.jdbc.DBException;
import com.daifukuamerica.wrxj.jdbc.DBResultSet;

import com.wynright.scanui.connectionFactory.DBConnection;

public class FromStation extends ScanField{


    @Override
    public boolean validate(){ 

        if(value.equals("")){ 
            errors.put("fromStationNumber", "Please scan/enter valid station"); 
        }

        String sql = "SELECT SDESTINATIONSTATION FROM ORDERHEADER WHERE SDESTINATIONSTATION = '" + getValue() + "'"; 
        DBResultSet results = null; 

        if(DBConnection.getWrxjConnection().isConnectionActive()){ 
            try {
                 results= DBConnection.getWrxjConnection().execute(sql, null);
            } catch (DBCommException | DBException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
        }

        if(results != null && results.getRowCount()!=0){ 
            isValidated = true; 
        }

        //TODO -- Add WRXJ server validate (JSON)

        return isValidated; 
    }

}

Tomcat 7Web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>RFUI</display-name>

  <listener>
    <listener-class>com.wynright.scanui.connectionFactory.DBConnectionService</listener-class>
</listener>

  <servlet>
    <servlet-name>ValidateFromStation</servlet-name>
    <servlet-class>com.wynright.scanui.action.ValidateFromStation
      </servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ValidateFromStation</servlet-name>
    <url-pattern>/ValidateFromStation/*</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>ValidateLogin</servlet-name>
    <servlet-class>com.wynright.scanui.action.ValidateLogin
      </servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ValidateLogin</servlet-name>
    <url-pattern>/ValidateLogin/*</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>ValidatePickingFromStation</servlet-name>
    <servlet-class>com.wynright.scanui.action.ValidatePickingFromStation
      </servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ValidatePickingFromStation</servlet-name>
    <url-pattern>/ValidatePickingFromStation/*</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>ValidatePickingToStation</servlet-name>
    <servlet-class>com.wynright.scanui.action.ValidatePickingToStation
      </servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ValidatePickingToStation</servlet-name>
    <url-pattern>/ValidatePickingToStation/*</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>ValidateSerialNumber</servlet-name>
    <servlet-class>com.wynright.scanui.action.ValidateSerialNumber
      </servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ValidateSerialNumber</servlet-name>
    <url-pattern>/ValidateSerialNumber/*</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>ValidateToLoad</servlet-name>
    <servlet-class>com.wynright.scanui.action.ValidateToLoad
      </servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ValidateToLoad</servlet-name>
    <url-pattern>/ValidateToLoad/*</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>ValidateToStation</servlet-name>
    <servlet-class>com.wynright.scanui.action.ValidateToStation
      </servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ValidateToStation</servlet-name>
    <url-pattern>/ValidateToStation/*</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>


RFI
com.wynright.scanui.connectionFactory.DBConnectionService
验证站
com.wynright.scanui.action.ValidateFromStation
验证站
/验证站/*
阿维泰洛金
com.wynright.scanui.action.ValidateLogin
阿维泰洛金
/阿维泰洛金/*
从火车站到火车站
com.wynright.scanui.action.validatePickFromStation
从火车站到火车站
/从火车站到火车站/*
王者地位
com.wynright.scanui.action.ValidatePickingToStation
王者地位
/王者地位/*
验证序列号
com.wynright.scanui.action.ValidateSerialNumber
验证序列号
/验证序列号/*
验证加载
com.wynright.scanui.action.ValidateToLoad
验证加载
/验证加载/*
验证站
com.wynright.scanui.action.validateStation
验证站
/验证站/*
index.html
index.htm
index.jsp
default.html
default.htm
default.jsp

我认为设置属性有问题。我没有找到你设置属性的地方。您必须使用请求对象在JSP或servlet中设置属性

您提到过使用Scanner设置变量。但是它必须设置请求对象。是你干的吗？然后您将使用request.getAttribute（）方法获得它

希望能有帮助

我想我已经解决了这个问题。我想我把整个豆子都用错了。我仍然有可能错误地使用了HttpSession、HttpServletRequest和HttpServletResponse的全部目的，因此如果我是某人，请提供建议

我的问题是，我试图使用jsp标记加载我的bean，如下所示：

<jsp:useBean id="fromStation" class="com.wynright.scanui.model.FromStation" scope="request"/>

然后在我的JSPstation.JSP中，我可以访问bean directyle，而无需使用表达式语言使用${bean.beanvalue}标记（有关此方面的更多信息：），以下是我在我的station.JSP中访问这些值时使用的代码：

<!-- 
    @author - Dylan Stout 
    7/19/2016

    Description: Station Screen -- Takes scanner input to three fields: fromStation, toStation, toLoad
    Javascript is used to handle cursor position,incrementing fields, and button-press for load releasing. 
    PickProcess java bean holds the session information necessary to verify and send/recieve messages to wrxj 
    back-end. 

    Each input field is it's own form so no handling for carriage returns is needed (symbol guns usually
    send carriage return after scan) 

 -->
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta name="viewport" content="width=240, height=320, user-scalable=no,
initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0" />
<link type="text/css" rel="stylesheet" href="css/scanui.css">
<script type="text/javascript" src="scripts/jquery-3.1.0.min.js"></script>
<script type="text/javascript"  src="scripts/formController.js"></script>
<script type="text/javascript"  src="scripts/station.js"></script>
<noscript>JavaScript is off. Please enable to use ScanUI.</noscript>
<title>Station Pick - Scan UI</title>
</head>
<body onload="onBodyLoad()">
<table cellpadding=4 cellspacing=2 id="stationTable">
        <th bgcolor="#CCCCFF" colspan=2><font size=2>Station Pick : ${pickProcess.userName}</font></th>
        <tr bgcolor="#c8d8f8">
            <td valign=top>
                <form name="fromStation" action="${pageContext.request.contextPath}/ValidateFromStation" method=post id="fromStationForm">
                    From Station: <input type="text" name="value" id="fromStation" value='${pickProcess.fromStation}' size=5 maxlength=5 tabindex="1"> 
                    <font size=2 color=red><br> ${fromStation.error}</font>
                </form>
            </td>
            <td valign=top>
                <form name="toStation" action="${pageContext.request.contextPath}/ValidateToStation" method=post id="toStation">
                    To Station: <input type="text" name="value" value='${pickProcess.toStation}' size=5 maxlength=5 tabindex="2"> 
                    <font size=2 color=red><br> ${toStation.error}</font>
                </form>
            </td>
        </tr>
        <tr bgcolor="#c8d8f8">
            <td valign=top colspan="2"><form name="toLoad" action="${pageContext.request.contextPath}/ValidateToLoad" method=post id="toLoad">
                    To Load: <input type="text" name="value"
                        value='${pickProcess.toLoad}' size=34 maxlength=30 tabindex="3"> 
                    <font size=2 color=red><br> ${toLoad.error}</font>
                </form></td>
        </tr>
    </table>



</body>
</html>

然后，我可以在该会话存在的任何位置检索它：

PickProcess pickProcess = (PickProcess)session.getAttribute("pickProcess");

如果没有收到空值，我无法检索会话属性。

我以为这就是我通过设置“”所做的，但可能我弄错了。不管怎样，我想我已经想出了一个解决方案，见上文。