Question

我知道我的Jasper报告正在从我的数据库正确读取，因为它与我的数据库具有相同的行数。但是，它使用＆＃34; null＆＃34;填充所有参数。为什么要这样做？

我的代码：

Connection connection;
    Statement stmt;
    ResultSet rs;

    try {

        String query = "SELECT CertificateCode, FirstName, LastName, IssueDate, ExpirationDate, Used FROM giftcertificates";
        //System.out.println("Query created. Connecting to driver...");
        Class.forName("org.h2.Driver");
        //System.out.println("Connected to driver. Establishing connection to database...");
        connection = DriverManager.getConnection("jdbc:h2:./GiftCertificateManagerDatabase;AUTO_SERVER=TRUE");
        //System.out.println("Database connection established. Creating statement...");
        stmt = connection.createStatement();
        //System.out.println("Statement created. Executing query...");
        rs = stmt.executeQuery(query);
        //System.out.println("Query executed. Creating data source with result set...");
        JRResultSetDataSource rsdt = new JRResultSetDataSource(rs);
        //System.out.println("Jasper Report data source created.");
        //System.out.println("Creating JasperReport and JasperPrint...");
        JasperReport jasperReport;
        JasperPrint jasperPrint;
        //System.out.println("JasperReport and JasperPrint created. Compiling report...");

        jasperReport = JasperCompileManager.compileReport("Reports/GiftCertificateReport.jrxml");
        //System.out.println("Report compiled. Filling report with appropriate information...");
        jasperPrint = JasperFillManager.fillReport(jasperReport, new HashMap(), rsdt);
        //System.out.println("Report filled. Creating viewer...");
        JasperViewer view = new JasperViewer(jasperPrint);
        //System.out.println("Viewer created. Preparing to display...");
        view.setVisible(true);
        //System.out.println("Viewer displayed. Preparing to close connection...");
        System.out.println(rs);
        connection.close();
        //System.out.println("Connection closed.");
    } catch (ClassNotFoundException | SQLException | JRException ex) {
        ex.printStackTrace();
    }

Answer 1

我认为Jasper正在使用null填充所有参数，因为您将空映射传递给fill方法：

jasperPrint = JasperFillManager.fillReport(jasperReport, new HashMap(), rsdt);

你必须用你想要的参数填充那个HashMap。

JasperFillManager.fillReport apidoc

为什么我的Jasper报告显示几个空值？

1 个答案: