java - ClassCastException 发生但没有任何适当的细节

Question

我正在使用动态报告，而动态报告又使用 Jasper Reports 生成 pdf。我的代码中出现 ClassCastException，因为我无法理解其中的任何内容。如果有人知道错误可能出在哪里，请帮助我。很抱歉，如果我错过任何细节，因为我赶时间。随时询问任何需要的额外细节。

这是发生错误的代码

public void createPdf(OutputStream out) {
    SubreportBuilder subreport = cmp.subreport(new SubreportExpression())
            .setDataSource(new SubreportDataSourceExpression());

    JasperPdfExporterBuilder pdfExporter = Exporters.pdfExporter("D:\\PDF\\report.pdf");
    try {
        report()
                .detail(
                subreport,
                cmp.verticalGap(20))
                .pageHeader(PdfTemplate.headerPortraitComponent)
                .pageFooter(PdfTemplate.footerPortraitComponent)
                .setDataSource(createDataSource())
                .toPdf(out);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

这是错误输出

Jun 28, 2013 5:09:32 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [CMCaseServlet] in context with path [] threw exception
net.sf.jasperreports.engine.JRRuntimeException: net.sf.jasperreports.engine.fill.JRExpressionEvalException: Error evaluating expression : 
    Source text : $F{column1}
    at net.sf.jasperreports.engine.fill.JRFillSubreport.prepare(JRFillSubreport.java:782)
    at net.sf.jasperreports.engine.fill.JRFillElementContainer.prepareElements(JRFillElementContainer.java:331)
    at net.sf.jasperreports.engine.fill.JRFillBand.fill(JRFillBand.java:384)
    at net.sf.jasperreports.engine.fill.JRFillBand.fill(JRFillBand.java:358)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:2046)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:778)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportContent(JRVerticalFiller.java:308)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:155)
    at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:909)
    at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:841)
    at net.sf.jasperreports.engine.fill.JRFiller.fill(JRFiller.java:88)
    at net.sf.jasperreports.engine.JasperFillManager.fill(JasperFillManager.java:653)
    at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:969)
    at net.sf.dynamicreports.jasper.builder.JasperReportBuilder.toJasperPrint(JasperReportBuilder.java:308)
    at net.sf.dynamicreports.jasper.builder.JasperReportBuilder.show(JasperReportBuilder.java:327)
    at cliff.reports.CMCaseReport.createPdf(CMCaseReport.java:58)
    at cliff.servlet.CMCaseServlet.processRequest(CMCaseServlet.java:366)
    at cliff.servlet.CMCaseServlet.doGet(CMCaseServlet.java:611)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at cliff.filter.LoginFilter.doFilter(LoginFilter.java:37)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1812)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)
Caused by: net.sf.jasperreports.engine.fill.JRExpressionEvalException: Error evaluating expression : 
    Source text : $F{column1}
    at net.sf.jasperreports.engine.fill.JREvaluator.evaluate(JREvaluator.java:203)
    at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:591)
    at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:559)
    at net.sf.jasperreports.engine.fill.JRFillElement.evaluateExpression(JRFillElement.java:966)
    at net.sf.jasperreports.engine.fill.JRFillTextField.evaluateText(JRFillTextField.java:456)
    at net.sf.jasperreports.engine.fill.JRFillTextField.evaluate(JRFillTextField.java:440)
    at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:259)
    at net.sf.jasperreports.engine.fill.JRFillFrame.evaluate(JRFillFrame.java:149)
    at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:259)
    at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:455)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:2044)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:778)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:288)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:151)
    at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:909)
    at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:841)
    at net.sf.jasperreports.engine.fill.JRFillSubreport.fillSubreport(JRFillSubreport.java:655)
    at net.sf.jasperreports.engine.fill.JRSubreportRunnable.run(JRSubreportRunnable.java:59)
    at net.sf.jasperreports.engine.fill.AbstractThreadSubreportRunner.run(AbstractThreadSubreportRunner.java:203)
    ... 3 more
Caused by: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
    at Report_1372410572739_904220.evaluate(Report_1372410572739_904220:202)
    at net.sf.jasperreports.engine.fill.JREvaluator.evaluate(JREvaluator.java:190)
    ... 21 more

更新

其他方法的代码

private static JRDataSource createDataSource() {
    return new JREmptyDataSource(7);
}

private class SubreportExpression extends AbstractSimpleExpression<JasperReportBuilder> {

    private static final long serialVersionUID = 1L;

    @Override
    public JasperReportBuilder evaluate(ReportParameters reportParameters) {
        int masterRowNumber = reportParameters.getReportRowNumber();
        JasperReportBuilder report = null;
        try {
            switch (masterRowNumber) {
                case 1:
                    report = getCaseReport();
                    break;
                case 2:
                    report = getRequestsReport();
                    break;
                case 3:
                    report = getObjectiveReport();
                    break;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return report;
    }
}

private class SubreportDataSourceExpression extends AbstractSimpleExpression<JRDataSource> {

    private static final long serialVersionUID = 1L;

    @Override
    public JRDataSource evaluate(ReportParameters reportParameters) {
        int masterRowNumber = reportParameters.getReportRowNumber();
        DRDataSource dataSource = null;
        try {

            switch (masterRowNumber) {
                case 1:
                    dataSource = getCaseDS();
                    break;
                case 2:
                    dataSource = getRequestsDS();
                    break;
                case 3:
                    dataSource = getObjectiveDS();
                    break;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return dataSource;
    }
}

private JasperReportBuilder getCaseReport() {
    JasperReportBuilder report = report();
    try {
        report
                .setTemplate(PdfTemplate.reportTemplate2)
                .title(cmp.text("CM Details").setStyle(PdfTemplate.bold12LeftStyle));

        for (int i = 1; i <= 4; i++) {
            report.addColumn(col.column("", "column" + i, type.stringType()));
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return report;
}



private DRDataSource getCaseDS() {
    String[] columns = new String[4];
    for (int i = 0; i < 4; i++) {
        columns[i] = "column" + (i + 1);
    }
    DRDataSource dataSource = new DRDataSource(columns);

    try {
        if (c== null) {  // c is a instance variable initiated by constructor
            c= new CMCase();
        }

        Object[] values = new Object[4];

        values[0] = "ID";
        values[1] = c.getOd(); // String
        values[2] = "Person In Charge";
        values[3] = c.getPicId();
        dataSource.add(values);

        values[0] = "Customer ID";
        values[1] = c.getCustomerId();  // String
        values[2] = "Assign Date";
        values[3] = c.getAssignDate(); // date already parsed to String from class
        dataSource.add(values);

        values[0] = "Account Number";
        values[1] = c.getAccountNumber(); // String
        values[2] = "Counter";
        values[3] = Integer.toString(c.getCounter());  // int parsed to String
        dataSource.add(values);

    } catch (Exception e) {
        e.printStackTrace();
    }
    return dataSource;
}

在调试模式下，错误发生在 when masterRowNumberis1本身所以没有给出剩余的方法

score 1 · Accepted Answer

给定的异常非常清楚

java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

JVM 期待 ajava.lang.String而你给它一个java.lang.Integer. Integer不能强制转换为a String。

这必须与您的模板或提供给模板的数据有关。

score 0 · Accepted Answer

例外情况是：Jasper 期望您的数据源中的某个地方是一个 int，但您给了它一个字符串。
也许您必须检查您提供给报告的数据。

score 0 · Accepted Answer

模板中的字段或参数需要定义类型的对象。您可能很难找到导致问题的原因。这是我在 Eclipse 中跟踪它的一种方式：

ClassCastException为（例如通过单击控制台中的异常类）创建 Java 异常断点
当调试器停止时，尝试在调试视图中向上调用堆栈，直到在变量视图中找到“表达式”变量。
直到你发现有问题的变量或属性名
在 iReport 中找到它并修复“字段类”或“参数类”

在此处输入图像描述

或者，在 jrxml 文件中搜索“to”类，可能数量不多。如果“A 不能转换为 B”，请搜索 B。

java - ClassCastException 发生但没有任何适当的细节

3 回答 3

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