Jsf 从DynamoDB填充数据表

我试图用从DynamoDB表（amazonnosqldb）检索的数据填充JSF数据表。目前，在扫描结果的迭代之前，一切都很正常。调试器显示我的scanResult有一个所有帐户的列表，但当我尝试迭代这些结果以构建我的列表时，似乎没有任何内容添加到allUserSummary列表中，我最终出现了一个nullpointer异常

基本用户POJO：

public class User {

private String uuid;

   public User(String uuid) {
       this.uuid = uuid;
   }
}

托管bean：

private List<User> allUserSummary;
private List<String> uuid;
private User selectedUser;

public List<User> getAllUserSummary() throws Exception {
    populateData();
    return allUserSummary;
}

private void populateData() throws Exception {

    // Create a new AmazonDynamoDBClient and mapper
    AmazonDynamoDBClient client = dynamoClient.getDynamoClient();
    DynamoDBMapper mapper = new DynamoDBMapper(client);


    try {
        // Create a new scan expression and filter to find the required data from the db
        DynamoDBScanExpression scanExpression = new DynamoDBScanExpression();
        Map<String, Condition> scanFilter = new HashMap<String, Condition>();
        Condition scanCondition = new Condition().withComparisonOperator(ComparisonOperator.NOT_NULL);
        scanFilter.put("uuid", scanCondition);
        scanExpression.setScanFilter(scanFilter);

        // Run the scan
        List scanResults = mapper.scan(UserAccounts.class, scanExpression);

        // Iterate over the scanned results and add the required data to a new User
        for (Iterator it = scanResults.iterator(); it.hasNext();) {
            allUserSummary.add(new User(scanResults.get(1).toString()));
        }

    } catch (Exception e) {
        // TODO
    }

}

给你

将值设置为

update=“”

和

oncomplete=“”

或从按钮中删除它们

                    <pou:commandButton id="multiViewButton" 
                                       value="View" 
                                       icon="ui-icon-search"
                                       update="" 
                                       oncomplete=""/>  

。 . .

public List getAllUserSummary（）引发异常{
返回摘要；
}

您是否初始化了allUserSummary列表？像这个私有列表一样，allUserSummary=newArrayList（）@Daniel是的，我还将init（）的内容移动到了getAllUserSummary（）中。事实上，我在错误出现的那个阶段没有得到空指针：java.lang.IllegalArgumentException:“！发布完整堆栈跟踪，并说明代码的哪一行是异常thrown@Daniel我已将堆栈跟踪添加到原始帖子中。我还编辑了代码，将代码移动到一个单独的方法中，并在getAllUserSummary（）中调用它来尝试跟踪错误。啊哈！已修复java.lang.IllegalArgumentException:“”。但是我仍然没有得到任何东西。scanResults正在返回列表，但此行似乎没有将值添加到allUserSummary列表：

allUserSummary.add（新用户（scanResults.get（1.toString（）））现在是一个不同的问题，好的，调试一下，你看到了什么错误？在右边放一些打印件。我在这里开始了一个新问题：
java.lang.IllegalArgumentException: ""
    at javax.faces.component.UIComponentBase.findComponent(UIComponentBase.java:570)
    at org.primefaces.util.ComponentUtils.findClientIds(ComponentUtils.java:244)
    at org.primefaces.renderkit.CoreRenderer.buildAjaxRequest(CoreRenderer.java:222)
    at org.primefaces.component.commandbutton.CommandButtonRenderer.encodeMarkup(CommandButtonRenderer.java:81)
    at org.primefaces.component.commandbutton.CommandButtonRenderer.encodeEnd(CommandButtonRenderer.java:53)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1764)
    at org.primefaces.component.datatable.DataTableRenderer.encodeFacet(DataTableRenderer.java:839)
    at org.primefaces.component.datatable.DataTableRenderer.encodeTFoot(DataTableRenderer.java:823)
    at org.primefaces.component.datatable.DataTableRenderer.encodeRegularTable(DataTableRenderer.java:247)
    at org.primefaces.component.datatable.DataTableRenderer.encodeMarkup(DataTableRenderer.java:224)
    at org.primefaces.component.datatable.DataTableRenderer.encodeEnd(DataTableRenderer.java:108)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1764)
    at javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1757)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:402)
    at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:288)
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1542)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:343)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)
    at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
    at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
    at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
    at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
    at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)
    at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)
    at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)
    at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)
    at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:380)
    at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:849)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:746)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1045)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:228)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:680)

                    <pou:commandButton id="multiViewButton" 
                                       value="View" 
                                       icon="ui-icon-search"
                                       update="" 
                                       oncomplete=""/>  

private List<User> allUserSummary = new ArrayList<User>();

@PostConstruct
public void populateData() throws Exception {

public List<User> getAllUserSummary() throws Exception {
    return allUserSummary;
}