jsf - Primefaces JSF java.lang.NullPointerException：参数错误：参数文本为空

Question

我将 JSF 2.0 与 Primefaces 3.4.2 一起使用，当我运行我的应用程序时，出现以下异常

java.lang.NullPointerException: Argument Error: Parameter text is null
    at com.sun.faces.renderkit.html_basic.HtmlResponseWriter.writeText(HtmlResponseWriter.java:877)
    at org.primefaces.component.datatable.DataTableRenderer.encodeFilter(DataTableRenderer.java:450)
    at org.primefaces.component.datatable.DataTableRenderer.encodeColumnHeader(DataTableRenderer.java:360)
    at org.primefaces.component.datatable.DataTableRenderer.encodeThead(DataTableRenderer.java:551)
    at org.primefaces.component.datatable.DataTableRenderer.encodeRegularTable(DataTableRenderer.java:218)
    at org.primefaces.component.datatable.DataTableRenderer.encodeMarkup(DataTableRenderer.java:192)
    at org.primefaces.component.datatable.DataTableRenderer.encodeEnd(DataTableRenderer.java:74)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)

JSF 代码片段

 <p:column id="empName" headerText="Name"  filterBy="#{emp.empName}"  
                            filterOptions="#{myMB.empFilter}"  
                            filterMatchMode="exact">
                            <h:outputText value="#{emp.empName}"/> 
                        </p:column>

在我的 ManagedBean

public Map<String,String> loadNames() {    
        names = new LinkedHashMap<String,String>();
        names.put("Smith", "S");
        names.put("Jones", "J");        
        return names;    
    }

private SelectItem[] empFilter;

public void init() {
empFilter= new SelectItem[loadNames().size() + 1];
        empFilter[0] = new SelectItem("", "Select");
        for (int i=1; i< empFilter.length; i++) {
            empFilter[i] = new SelectItem(loadNames().get(i-1), loadNames().get(i-1));
    }

}

Answer 1

您没有从您loadNames()的底部循环中正确获取值。

例子 ：

Map<String,String> map = new LinkedHashMap<String,String>();
map.put("Smith", "S");
map.put("Jones", "J");

System.out.println(map.get(0));

将返回null。

你需要像这样改变你的循环：

public void init()
{
    empFilter= new SelectItem[loadNames().size() + 1];
    empFilter[0] = new SelectItem("", "Select");
    int i = 1;

    for(Map.Entry<String,String> entry : loadNames().entrySet())
    {
        empFilter[i++] = new SelectItem(entry.getKey(),entry.getValue());
        System.out.println(entry.getKey() + "/" + entry.getValue());
    }
}