已编辑的对象列表未在jsf中提交_Jsf

已编辑的对象列表未在jsf中提交

jsf

已编辑的对象列表未在jsf中提交,jsf,Jsf,托管Bean @SuppressWarnings("serial") @ManagedBean(name = "samplemanage") @RequestScoped public class SampleManage implements Serializable { private List<Sample> samplelist; /** * @return the samplelist */ public Lis

托管Bean

@SuppressWarnings("serial")
@ManagedBean(name = "samplemanage")
@RequestScoped
public class SampleManage implements Serializable
{

    private List<Sample>        samplelist;

    /**
     * @return the samplelist
     */
    public List<Sample> getSamplelist()
    {
        return samplelist;
    }

    /**
     * @param samplelist the samplelist to set
     */
    public void setSamplelist(List<Sample> samplelist)
    {
        this.samplelist = samplelist;
    }

    public void docklist(ComponentSystemEvent event)
    {   
        List<Sample> samplelist = new ArrayList<Sample>();
        for(int i = 0 ; i < 10 ; i++)
        {
            Sample sa = new Sample();
            sa.setName("sample"+i);
            samplelist.add(sa);
        }
        this.samplelist = samplelist;

        for(Sample sa1 : this.samplelist)
        System.out.println("inserted name is "+sa1.getName());
    }

    public void checkaction()
    {
        for(Sample sa : samplelist)
        System.out.println("output name is "+sa.getName());
    }

}

xhtml

<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:p="http://primefaces.org/ui">
<h:head>
    <f:event listener="#{samplemanage.docklist}" type="preRenderView" />
</h:head>
<h:body>
    <h:form>
        <center>
            <p:dataTable id="sample" var = "sample" value="#{samplemanage.samplelist}">

            <p:column  headerText="Name">
                <h:inputText value="#{sample.name}"></h:inputText>
            </p:column>

            </p:dataTable>
            <p:commandButton id="submit" value="Submit" type="submit" action="#{samplemanage.checkaction}">
            </p:commandButton>
        </center>
    </h:form>
</h:body>
</html>

2014年3月31日凌晨1:17:13 com.sun.faces.lifecycle.InvokeApplicationPhase执行警告：#{samplemanage.checkaction}:java.lang.NullPointerException javax.faces.FacesException:#{samplemanage.checkaction}:java.lang.NullPointerException

我需要从表单中获取编辑后的值并打印出来，我认为这是个好办法，但我不知道为什么它返回空指针异常。

这里我做错的是，您的bean是

@RequestScoped

，因此每个HTTP请求都将创建一个新的请求

创建页面时，

preRenderView

事件调用

docklist

，它实例化了

sampleList

属性并显示页面

当您提交表单时，框架将创建一个新bean，其中

sampleList

未分配对象，因此您将获得NPE

使bean

@viewscope

<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:p="http://primefaces.org/ui">
<h:head>
    <f:event listener="#{samplemanage.docklist}" type="preRenderView" />
</h:head>
<h:body>
    <h:form>
        <center>
            <p:dataTable id="sample" var = "sample" value="#{samplemanage.samplelist}">

            <p:column  headerText="Name">
                <h:inputText value="#{sample.name}"></h:inputText>
            </p:column>

            </p:dataTable>
            <p:commandButton id="submit" value="Submit" type="submit" action="#{samplemanage.checkaction}">
            </p:commandButton>
        </center>
    </h:form>
</h:body>
</html>

Mar 31, 2014 1:17:13 AM com.sun.faces.lifecycle.InvokeApplicationPhase execute
WARNING: #{samplemanage.checkaction}: java.lang.NullPointerException
javax.faces.FacesException: #{samplemanage.checkaction}: java.lang.NullPointerException