Java 使用JPQL语言在报告中使用聚合函数计数时出错

我的帐户发生了问题（我无法访问它！！！！），因此我将再次问我的问题：( 我无法在报告中的JPQL请求中使用聚合函数： 这是我的报告。jrxml

<?xml version="1.0" encoding="UTF-8"?>
<jasperReport xmlns="http://jasperreports.sourceforge.net/jasperreports" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports  http://jasperreports.sourceforge.net/xsd/jasperreport.xsd" name="Test" language="groovy" pageWidth="595" pageHeight="842" columnWidth="555" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20">
<property name="ireport.zoom" value="1.0"/>
<property name="ireport.x" value="0"/>
<property name="ireport.y" value="0"/>
<parameter name="priority" class="java.lang.String">
<defaultValueExpression><![CDATA[]]></defaultValueExpression>
</parameter>

<queryString language="ejbql">
    **<![CDATA[select count(j) as nb from Jiraissue j where j.priority='3']]>**
</queryString>
    <field name="nb" class="java.lang.Long"/>
<background>
    <band splitType="Stretch"/>
</background>
<title>
        <band height="79" splitType="Stretch">

    </band>
</title>
<pageHeader>
    <band height="35" splitType="Stretch"/>
</pageHeader>
<columnHeader>
    <band height="84" splitType="Stretch">
        <staticText>
            <reportElement x="28" y="0" width="100" height="20"/>
            <textElement/>
            <text><![CDATA[nb]]></text>
        </staticText>

    </band>
</columnHeader>
<detail>
    <band height="125" splitType="Stretch">
        <textField>
            <reportElement x="50" y="11" width="100" height="20"/>
            <textElement/>
            <textFieldExpression class="java.lang.Long">    <![CDATA[$F{nb}]]></textFieldExpression>
        </textField>
    </band>
</detail>
<columnFooter>
    <band height="45" splitType="Stretch"/>
</columnFooter>
<pageFooter>
    <band height="54" splitType="Stretch"/>
</pageFooter>
<summary>
    <band height="42" splitType="Stretch"/>
</summary>
</jasperReport>

错误：

net.sf.jasperreports.engine.JRException: Error retrieving field value from bean : nb
at    net.sf.jasperreports.engine.data.JRAbstractBeanDataSource.getBeanProperty(JRAbstractBeanDat    aSource.java:123)
at   net.sf.jasperreports.engine.data.JRJpaDataSource$PropertyReader.getValue(JRJpaDataSource.java:206)
at net.sf.jasperreports.engine.data.JRJpaDataSource.getFieldValue(JRJpaDataSource.java:131)
at net.sf.jasperreports.engine.fill.JRFillDataset.setOldValues(JRFillDataset.java:821)
at net.sf.jasperreports.engine.fill.JRFillDataset.next(JRFillDataset.java:785)
at net.sf.jasperreports.engine.fill.JRBaseFiller.next(JRBaseFiller.java:1482)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:126)
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:946)
at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:118)
at  net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:435)
at Reporting.ReportBean.main(ReportBean.java:41)
Caused by: java.lang.NoSuchMethodException: Unknown property 'nb' on class 'class  java.lang.Long'

---

请提供任何帮助：（

计数函数只能用于实体的字段，而不能用于实体本身。您可以选择任何字段进行计数，但它可能应该是主键，因为它永远不会为空。不过，以下查询应该可以工作

<![CDATA[select count(j.priority) as nb from Jiraissue j where j.priority='3']]>

<![CDATA[select count(j.priority) as nb from Jiraissue j where j.priority='3']]>