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使用this StackOverflow answer嘗試執行無提交形式。該頁面由一個selectomenu控件和一個表格組成。關於選擇的更改，我希望刷新表格主體。該頁面加載沒有問題，但是當選擇時我得到出現以下錯誤：在selectoneitem上的AJax回調失敗（NPE）
10:22:48,241 ERROR [[FacesServlet]] Servlet.service() for servlet FacesServlet threw exception: java.lang.NullPointerException
at com.sun.faces.context.PartialViewContextImpl.createPartialResponseWriter(PartialViewContextImpl.java:441) [jsf-impl-2.1.7-jbossorg-2.jar:]
at com.sun.faces.context.PartialViewContextImpl.access$300(PartialViewContextImpl.java:71) [jsf-impl-2.1.7-jbossorg-2.jar:]
at com.sun.faces.context.PartialViewContextImpl$DelayedInitPartialResponseWriter.getWrapped(PartialViewContextImpl.java:582) [jsf-impl-2.1.7-jbossorg-2.jar:]
at javax.faces.context.PartialResponseWriter.startDocument(PartialResponseWriter.java:115) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
at com.sun.faces.context.AjaxExceptionHandlerImpl.handlePartialResponseError(AjaxExceptionHandlerImpl.java:199) [jsf-impl-2.1.7-jbossorg-2.jar:]
at com.sun.faces.context.AjaxExceptionHandlerImpl.handle(AjaxExceptionHandlerImpl.java:123) [jsf-impl-2.1.7-jbossorg-2.jar:]
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:119) [jsf-impl-2.1.7-jbossorg-2.jar:]
at com.sun.faces.lifecycle.RestoreViewPhase.doPhase(RestoreViewPhase.java:116) [jsf-impl-2.1.7-jbossorg-2.jar:]
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) [jsf-impl-2.1.7-jbossorg-2.jar:]
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) [jbossweb-7.0.13.Final.jar:]
at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153) [jboss-as-web-7.1.1.Final.jar:7.1.1.Final]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368) [jbossweb-7.0.13.Final.jar:]
at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:505) [jbossweb-7.0.13.Final.jar:]
at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:445) [jbossweb-7.0.13.Final.jar:]
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930) [jbossweb-7.0.13.Final.jar:]
at java.lang.Thread.run(Thread.java:636) [rt.jar:1.6.0_18]
我使用JBoss的AS-7.1.1，和selectonmenu看起來是這樣的：
<h:selectOneMenu id="ship"
value="#{shipManager.current}">
<f:selectItems value="#{shipManager.list}"
var="ship"
itemValue="#{ship}"
itemLabel="#{ship.name}" />
<f:ajax listener="#{shipManager.changeShip}" />
</h:selectOneMenu>
如果我刪除ajax組件然後沒有問題，雖然（當然）shipManager未更新。
一旦我做了選擇，我想添加renderer部分來刷新我的表體。
非常感謝任何幫助。
史蒂夫
如這裏要求是我的XHTML代碼：
<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:ui="http://java.sun.com/jsf/facelets">
<h:head>
<title>Voyage Cruises</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<link type="text/css" rel="stylesheet" media="all" href="/css/screen.css"/>
<link type="text/css" rel="stylesheet" media="all" href="/css/cruise.css"/>
<script src="http://open.mapquestapi.com/sdk/js/v7.0.s/mqa.toolkit.js"></script>
<script src="js/map.js" ></script>
<script src="js/cruise.js" ></script>
</h:head>
<h:body>
<div id="page">
<div id="float-map">
<div id="map"></div>
</div>
<h:form id="ship-form">
<div id="ship-controls">
<div class="float-ctrls">
<a href="/ports.html" title="Find Ports"><img src="/images/action_search.png" alt="Find Ports"/></a>
</div>
<div>
<span id="ship-selector" >
<h:selectOneMenu id="ship"
value="#{shipManager.current}">
<f:selectItems value="#{shipManager.list}"
var="ship"
itemValue="#{ship}"
itemLabel="#{ship.name}" />
<f:ajax execute="ship" render="@form" listener="#{shipManager.changeShip}" />
</h:selectOneMenu>
</span>
<select id="month" />
<select id="year" />
<br />
<span class="input-container"><b>Tonnage:</b><input id="tonnage" type="text" size="6" value="30,277" /></span>
<span class="input-container"><b>Audit Time:</b><input id="audit" type="text" size="2" value="6" /></span>
<span class="input-container"><b>Fleet:</b><input id="fleet" type="text" size="20" value="P&O" /></span>
</div>
</div>
<table class="cruise">
<thead>
<tr>
<th class="date">Date</th>
<th class="port">Port</th>
<th class="arrive">Arrive</th>
<th class="depart">Depart</th>
</tr>
</thead>
<tbody>
<ui:repeat var="cruise"
value="#{cruiseManager.list}"
varStatus="table">
<tr class="#{table.even ? 'even' : 'odd'}">
<td class="date">
<h:outputFormat value="{0, date,d MMM}">
<f:param value="#{cruise.date}" />
</h:outputFormat>
</td>
<h:panelGroup rendered="#{null != cruise.port}">
<td class="port">#{cruise.port.name}</td>
<td class="arrive">
<h:outputFormat rendered="#{null != cruise.arrival}"
styleClass="#{cruise.arrivalEstimated ? 'est-time' : 'act-time'}"
value="{0, date,HH:mm}">
<f:param value="#{cruise.arrival}" />
</h:outputFormat>
</td>
<td class="depart">
<h:outputFormat rendered="#{null != cruise.departure}"
styleClass="#{cruise.departureEstimated ? 'est-time' : 'act-time'}"
value="{0, date,HH:mm}">
<f:param value="#{cruise.departure}" />
</h:outputFormat>
</td>
</h:panelGroup>
<h:panelGroup rendered="#{null == cruise.port}">
<td class="at-sea" colspan="3">At Sea</td>
</h:panelGroup>
</tr>
</ui:repeat>
</tbody>
</table>
</h:form>
</div>
</h:body>
</html>
而且ShipManager：
package com.nutrastat.voyager.web;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import javax.ejb.EJB;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
import javax.faces.event.AjaxBehaviorEvent;
import com.nutrastat.voyager.db.HarbourMasterLocal;
import com.nutrastat.voyager.db.ShipEntity;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@ManagedBean
@ViewScoped
public class ShipManager
implements Serializable {
static final long serialVersionUID = -3017226836104715117L;
private transient final Logger log;
private ShipEntity currentShip;
@EJB
private HarbourMasterLocal harbourMaster;
public ShipManager() {
log = LoggerFactory.getLogger(getClass());
}
public ShipEntity getCurrent() {
if (log.isInfoEnabled())
log.info("getCurrent(): " + currentShip);
return currentShip;
}
public void setCurrent(ShipEntity ship) {
if (log.isInfoEnabled())
log.info("setCurrent(" + currentShip + "): " + ship);
currentShip = ship;
}
public void changeShip(AjaxBehaviorEvent evt) {
if (log.isInfoEnabled())
log.info("Ship now: " + currentShip);
}
public List<ShipEntity> getList() {
try {
return harbourMaster.listShips();
} catch (Exception cause) {
log.error("Getting the list of ships", cause);
return new ArrayList<ShipEntity>(0);
}
}
}
嗨。我的堆棧跟蹤可能看起來不完整，但它就是這樣。由於我不需要存儲POJO，因此我將selectOneMenu轉換爲僅使用字符串。這並刪除尚未使用（但將需要）的其他選擇項目清除錯誤，現在一切正常。非常感謝。 – Dobbo