当我尝试传递我的报告连接时，为什么 get cannot be cast to net.sf.jasperreports.engine.JRDataSource？

Question

我的报告 jrxml 文件看起来像

<band height="256" splitType="Stretch">
            <componentElement>
                <reportElement x="0" y="0" width="555" height="50" uuid="eb5b00f3-c370-4c7f-bb10-b7589ff293ff"/>
                <jr:list xmlns:jr="http://jasperreports.sourceforge.net/jasperreports/components" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports/components http://jasperreports.sourceforge.net/xsd/components.xsd" printOrder="Vertical">
                    <datasetRun subDataset="listDataset" uuid="364ec058-5b7e-43e0-9272-92907dfba7f3">
                        <datasetParameter name="REPORT_DATE">
                            <datasetParameterExpression><![CDATA[$P{REPORT_DATE}]]></datasetParameterExpression>
                        </datasetParameter>
                        <dataSourceExpression><![CDATA[$P{REPORT_CONNECTION}]]></dataSourceExpression>
                    </datasetRun>
                    <jr:listContents height="50" width="555">
                        <staticText>
                            <reportElement x="1" y="2" width="100" height="20" uuid="cd4ed06d-2c04-4342-8cc2-ff7077621eb6"/>
                            <text><![CDATA[LABEL_VALUE]]></text>
                        </staticText>
                        <textField>
                            <reportElement x="101" y="2" width="129" height="20" uuid="d307fa41-0962-4b17-812d-774262e55e9e"/>
                            <textFieldExpression><![CDATA[$F{LABEL_VALUE}]]></textFieldExpression>
                        </textField>
                        <staticText>
                            <reportElement x="230" y="2" width="140" height="20" uuid="20989891-eb66-45ee-8fbb-b7c53a65f0fe"/>
                            <text><![CDATA[ATTRIBUTE_VALUE]]></text>
                        </staticText>
                        <textField>
                            <reportElement x="370" y="2" width="184" height="20" uuid="fa972e53-dc8a-402e-96ad-9428b402ccd8"/>
                            <textFieldExpression><![CDATA[$F{ATTRIBUTE_VALUE}]]></textFieldExpression>
                        </textField>
                    </jr:listContents>
                </jr:list>
            </componentElement>
</band>

但是我得到了一个 ClassCastException，

java.lang.ClassCastException: org.jboss.jca.adapters.jdbc.jdk6.WrappedConnectionJDK6 cannot be cast to net.sf.jasperreports.engine.JRDataSource

我想不通，为什么？

Answer 1

来自 JasperReports api JRDatasetRun

A dataset run declaration supplies the values for the dataset parameters as well as the data source through which the dataset will iterate. Optionally, a java.sql.Connection can be passed to the dataset instead of a JRDataSource instance, when there is a SQL query associated with the dataset. This query is executed by the engine using the JDBC connection and the java.sql.ResultSet object obtained is iterated through.

结论当你运行一个数据集datasetRun你可以：

使用 dataSourceExpression 标签传递 JRDatasource
使用 connectionExpression 标签传递 JDBC 连接
不传递任何内容。

所以你做错了什么？

您在 dataSourceExpression 标记而不是 connectionExpression 标记中传递 JDBC 连接，JasperReports 希望它是 JRDatasource 并尝试将其转换为 JRDatasource。

如果您想传递报告连接，您应该使用 connectionExpression，如下所示。

<datasetRun subDataset="listDataset" uuid="364ec058-5b7e-43e0-9272-92907dfba7f3">
    <datasetParameter name="REPORT_DATE">
       <datasetParameterExpression><![CDATA[$P{REPORT_DATE}]]></datasetParameterExpression>
    </datasetParameter>
    <connectionExpression><![CDATA[$P{REPORT_CONNECTION}]]></connectionExpression>
</datasetRun>

当我尝试传递我的报告连接时，为什么 get cannot be cast to net.sf.jasperreports.engine.JRDataSource？

Why do I get cannot be cast to net.sf.jasperreports.engine.JRDataSource when I try to pass my report connection?

connection

jasper-reports

dataset

classcastexception