1. 技术文章
  2. The document has no pages. Jasper Report

The document has no pages. Jasper Report

由 删除回忆录丶 提交于 2019-12-06 01:50:42

Firstly, resource management...

You should only open a single connection to the database if you can. Make sure you close it before the application is closed. The connection process can be expensive, so you only really want to do it when you absolutely have to...

You close your resources once you have finished with them. This is best achieved by using a try-finally block...

private Connection con;

protected void close() throws SQLException {
    if (con != null) {
        con.close();
    }
}

protected Connection getConnection() throws ClassNotFoundException, SQLException {
    if (con == null) {
        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
        String url = "jdbc:odbc:*****";
        String user = "******";
        String pass = "******";
        Connection con = DriverManager.getConnection(url, user, pass);
    }
    return con;
}

private void search() throws Exception {

    Statement state = null;
    ResultSet rs = null;

    try {

        state = getConnection().createStatement();

        rs = state.executeQuery("SELECT "
                + "pIDNo AS 'Patient ID',"
                + "pLName AS 'Last Name',"
                + "pFName AS 'First Name',"
                + "pMI AS 'M.I.',"
                + "pSex AS 'Sex',"
                + "pStatus AS 'Status',"
                + "pTelNo AS 'Contact No.',"
                + "pDocID AS 'Doctor ID',"
                + "pAddr AS 'St. No.',"
                + "pStreet AS 'St. Name',"
                + "pBarangay AS 'Barangay',"
                + "pCity AS 'City',"
                + " pProvince AS 'Province',"
                + " pLNameKIN AS 'Last Name',"
                + "pFNameKIN AS 'First Name',"
                + "pMIKIN AS 'M.I.',"
                + "pRelationKIN AS 'Relation',"
                + "pTotalDue AS 'Total Due'"
                + " FROM dbo.Patients");
        ResultSetMetaData rsmetadata = rs.getMetaData();
        int columns = rsmetadata.getColumnCount();

        DefaultTableModel dtm = new DefaultTableModel();
        Vector column_name = new Vector();
        Vector data_rows = new Vector();

        for (int i = 1; i < columns; i++) {
            column_name.addElement(rsmetadata.getColumnName(i));
        }
        dtm.setColumnIdentifiers(column_name);

        while (rs.next()) {
            data_rows = new Vector();
            for (int j = 1; j < columns; j++) {
                data_rows.addElement(rs.getString(j));
            }
            dtm.addRow(data_rows);
        }
        tblPatient.setModel(dtm);

    } finally {
        try {
            rs.close();
        } catch (Exception e) {
        }
        try {
            state.close();
        } catch (Exception e) {
        }
    }
}

Now to the problem at hand...

It appears you have create two references to con. One as class field and one as a method variable (in search).

You are then passing con to Jasper Reports, which I suspect is null. Instead you should use the getConnection() as outlined above.

public void reportviewer() {
    try{
        String report = "C:\\Users\\cleanfuel\\Documents\\NetBeansProjects\\StringManipulation\\src\\stringmanipulation\\report1.jrxml";
        JasperReport jasp_report = JasperCompileManager.compileReport(report);
        JasperPrint jasp_print = JasperFillManager.fillReport(jasp_report, null, getConnection());
        JasperViewer.viewReport(jasp_print);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

Updated with background worker...

A report can take some time to compile and fill. You should off load this work to a background thread so it doesn't interfere with your UI (or make it look like you application as hung).

The simplest solution would be to use a SwingWorker. It has functionality to resync the threads with the UI

public void reportviewer() {
    // Disable any UI components you don't want the user using while
    // the report generates...
    new ReportWorker().execute();
}

public class ReportWorker extends SwingWorker<JasperPrint, Void> {

    @Override
    protected JasperPrint doInBackground() throws Exception {
        String report = "C:\\Users\\cleanfuel\\Documents\\NetBeansProjects\\StringManipulation\\src\\stringmanipulation\\report1.jrxml";
        JasperReport jasp_report = JasperCompileManager.compileReport(report);
        JasperPrint jasp_print = JasperFillManager.fillReport(jasp_report, null, getConnection());
        return jasp_print;
    }

    @Override
    protected void done() {
        try {
            JasperPrint jasp_print = get();
            JasperViewer.viewReport(jasp_print);
        } catch (Exception exp) {
            exp.printStackTrace();
        }
        // Renable any UI components you disabled before the report run
    }
}

Take a look at Concurrency in Swing for more details.

Hints

If you can pre-compile the report and load it (rather the loading the XML), it will make the report process quicker.

标签
java
swing
sql-server-2005
jasper-reports
netbeans-7
易学教程内所有资源均来自网络或用户发布的内容，如有违反法律规定的内容欢迎反馈！
该文章没有解决你所遇到的问题?点击提问,说说你的问题,让更多的人一起探讨吧!