Primefaces拖拽行触发IndexOutOfBoundException问题求助

使用Primefaces的draggableRows结合onRowReorder事件实现行拖拽时，抛出IndexOutOfBoundsException，但点击另一个页面的保存按钮无此异常。

Controller.java #

public void onRowReorder(ReorderEvent event) {  

    FacesContext.getCurrentInstance();
    int tindex = event.getToIndex();

    List<DocumentPrintCollection> printCollectionsSorted = getPrintCollectionsSorted();
    DocumentPrintCollection printCollection = printCollectionsSorted.get(tindex);
    int newSort = printCollection.getSort();

    printCollection.setSort(newSort);
    
}

viewDocument.xhtml #

<div id="#{cc.clientId}">
    <p:dataTable id="printcollection" 
                 value="#{cc.attrs.printCollection}"
                 var="collection" rowIndexVar="rowIndex" first="0"
                 reflow="true"
                 sortBy="#{printCollection.sort}"
                 sortOrder="ascending"
                 draggableRows="true"
                 widgetVar="printcollection">
        <p:ajax event="rowReorder" listener="#{cc.attrs.model.onRowReorder}" process="@this"/>

MainPage.xhtml #

<p:tab id="doclist" title="Reorder Document list">
                <div jsf:id="printlist" class="doc_materials">
                    <div class="ui-g">
                        <div class="ui-g-12">
                            <vwprn:viewDocument model="#{maskDocMaterialsController}"
                                                       printCollection="#{maskDocMaterialsController.printCollections}"
                                                       documents="#{maskDocMaterialsController.realDocuments}"
                                                       readOnly="#{maskDocMaterialsController.readOnly}"
                                                       documentNullText="no Dokument"/>
                        </div>
                    </div>
                    <h:panelGroup layout="block" rendered="#{not maskDocMaterialsController.readOnly}">
                        <div class="footer-column">             
                            <p:commandButton id="btnSavePrintCollectionDocumentsList" value="Save" icon="fa fa-check" 
                                             action="#{maskDocMaterialsController.save}"
                                             process="@this" update="printlist"/>
                        </div>
                    </h:panelGroup>
                </div>
            </p:tab>

Message: toIndex = 2
StackTrace: java.lang.IndexOutOfBoundsException: toIndex = 2
at java.base/java.util.AbstractList.subListRangeCheck(AbstractList.java:507)
at java.base/java.util.ArrayList.subList(ArrayList.java:1108)
at org.primefaces.component.datatable.feature.DraggableRowsFeature.decode(DraggableRowsFeature.java:74)
at org.primefaces.component.datatable.DataTableRenderer.decode(DataTableRenderer.java:72)
at javax.faces.component.UIComponentBase.decode(UIComponentBase.java:509)
at org.primefaces.component.api.UIData.processDecodes(UIData.java:117)
at com.sun.faces.context.PartialViewContextImpl$PhaseAwareVisitCallback.visit(PartialViewContextImpl.java:606)
at com.sun.faces.component.visit.PartialVisitContext.invokeVisitCallback(PartialVisitContext.java:159)
at org.primefaces.component.api.UIData.visitTree(UIData.java:691)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at javax.faces.component.UINamingContainer.visitTree(UINamingContainer.java:150)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at org.primefaces.component.api.UITabPanel.visitTree(UITabPanel.java:939)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at javax.faces.component.UIForm.visitTree(UIForm.java:355)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1468)
at com.sun.faces.context.PartialViewContextImpl.processComponents(PartialViewContextImpl.java:400)
at com.sun.faces.context.PartialViewContextImpl.processPartial(PartialViewContextImpl.java:261)
at org.primefaces.context.PrimePartialViewContext.processPartial(PrimePartialViewContext.java:65)
at javax.faces.component.UIViewRoot.processDecodes(UIViewRoot.java:1008)
at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:55)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:76)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:177)
at javax.faces.webapp.FacesServlet.executeLifecyle(FacesServlet.java:707)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:451)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1637)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:259)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:167)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:757)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:577)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:158)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:372)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:239)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:520)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:217)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:182)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:156)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:201)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:95)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:260)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:177)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:109)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:88)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:53)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:524)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:89)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:94)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:33)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:114)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:569)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:549)
at java.base/java.lang.Thread.run(Thread.java:833)

异常根源 #

从堆栈可见，异常发生在Primefaces的DraggableRowsFeature.decode方法调用subList时，传入的toIndex=2超出了后端列表的实际长度，导致越界。核心原因是前端拖拽时传递的索引与后端维护的列表状态不一致。

具体问题点及修复方案 #

1. DataTable排序变量名错误

   • 代码中sortBy="#{printCollection.sort}"使用了错误的变量名，DataTable的var属性是collection，正确的表达式应为sortBy="#{collection.sort}"。这个错误会导致排序逻辑异常，前端显示的列表顺序与后端列表顺序不匹配，拖拽时索引对应关系混乱。
   • 修复：修改viewDocument.xhtml中的sortBy属性。

2. getPrintCollectionsSorted()返回列表不一致

   • 如果getPrintCollectionsSorted()每次调用都从数据库重新查询或创建新的列表实例，会导致该列表与DataTable绑定的#{cc.attrs.printCollection}（即maskDocMaterialsController.printCollections）不是同一个实例，长度或元素顺序可能不一致，拖拽时toIndex超出列表长度。
   • 修复：确保getPrintCollectionsSorted()返回的是maskDocMaterialsController.printCollections的同一个实例，或者在拖拽事件处理前同步两者状态。

3. onRowReorder方法逻辑无效

   • 当前代码中printCollection.setSort(newSort);是将元素的sort值设为自身原有的sort值，完全没有实现拖拽后的排序更新逻辑。正确的做法是根据拖拽后的新顺序，重新计算所有元素的sort值（比如从0开始递增）。
   • 修复示例：

     public void onRowReorder(ReorderEvent event) {  
         List<DocumentPrintCollection> printCollections = getPrintCollections(); // 使用DataTable绑定的列表
         // 重新设置排序值
         for (int i = 0; i < printCollections.size(); i++) {
             printCollections.get(i).setSort(i);
         }
     }
     

4. 确保后端列表与前端显示一致

   • 检查maskDocMaterialsController.printCollections的长度是否与前端DataTable显示的行数一致，避免因分页、过滤或数据加载逻辑导致后端列表元素缺失。

内容的提问来源于stack exchange，提问作者Md101