iReport+jasperReport之客户端打印

          jasperReport客户端采用applet，applet和activeX插件的区别大家搜一下，有一堆东西可以借鉴，下载jasperreports-3.0.0，在相应的sample OR demo（记得不清了）中可以找到jasperReport 实现的客户端打印demo，下来就来分析下具体实现。
  新建一print.js文件:

function loadApplet(applet_URL) {
    var URL = applet_URL + "/applets/jre-1_5_0_18-windows-i586-p.exe";
    document.write('<OBJECT id="myApplet" name="myApplet"');
    document.write('classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93" WIDTH="0" HEIGHT="0" MAYSCRIPT name="myApplet"');
    document.write('codebase='+ URL +'>');
    document.write('<PARAM NAME="CODE" VALUE="org.bulktree.report.print.applet.PrinterApplet" />');
    document.write('<PARAM NAME="CODEBASE" VALUE="../applets" />');
    document.write('<PARAM NAME="ARCHIVE" VALUE="jasperreports-3.0.1-applet.jar" />');
    document.write('<PARAM NAME="type" VALUE="application/x-java-applet;version=1.5.0" />');
    document.write('<PARAM NAME="scriptable" VALUE="false" />');
    document.write('<PARAM NAME="REPORT_URL" VALUE="../report.view">');
    document.write('no support java');
    document.write('<comment>');
    document.write('<embed type="application/x-java-applet;version=1.5.0"');
    document.write('CODE="org.bulktree.report.print.applet.PrinterApplet"');
    document.write('JAVA_CODEBASE="applets" ARCHIVE="jasperreports-3.0.1-applet.jar"');
    document.write('scriptable=false');
    document.write('pluginspage='+ URL +'>');
    document.write('<noembed></noembed>');
    document.write('</embed>');
    document.write('</comment>');
    document.write('</OBJECT>');
}

     URL为一个固定的路径，是为了下载/applets/jre-1_5_0_18-windows-i586-p.exe（JRE运行环境）而存在的，也可以使用外网从sun公司网站下载，
     REPORT_URL 为applet所要访问的地址，在工程的web.xml配置/report.view如下servlet即可，此servet可接收applet参数，生成jasperPrint对象，并传递到客户端applet中进行打印或者预览。
  servlet配置如下：

<servlet>
                <servlet-name>ReportServlet</servlet-name>
        <servlet-class>org.bulktree.report.print.applet.ReportServlet</servlet-class>
    </servlet>
<servlet-mapping>
        <servlet-name>ReportServlet</servlet-name>
        <url-pattern>/report.view</url-pattern>
    </servlet-mapping>

ReportServlet核心代码就是根据业务找到对应的模板文件填充数据生成jasperPrint对象，产生的jasperPrint对象以对象流的形式发送给客户端，核心代码如下：

// 生成jasperPrint对象
            JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport,
                    mapParam, new JREmptyDataSource());

//组装流
response.setContentType("application/octet-stream");
                response.setBufferSize(8986000);
                ServletOutputStream outStream = response.getOutputStream();
                ObjectOutputStream oos = new ObjectOutputStream(outStream);
                oos.writeObject(jasperPrint);

当然，客户端的applet使用如下：

/**//*
                     * applet与Servlet交互 URL传递页面传来的参数请求服务器Servlet
                     * 把applet传递的参数追加到servlet中 2008-10-14 laoshulin
                     */

                    url = new URL(getCodeBase(), requestUrl + "?printView=true"
                            + paraStr);

                    if (url == null) {
                        JOptionPane.showMessageDialog(this,
                                "Source URL not specified");
                    } else {
                        InputStream in = url.openStream();
                        ObjectInputStream objIn = new ObjectInputStream(in);
                        Object obj = objIn.readObject();
                        if (obj instanceof JasperPrint) {

                        } else {
                            JOptionPane.showMessageDialog(this, obj.toString());
                            return;
                        }

                        if (jasperPrint == null) {
                            // 根据Servlet返回的URL（ObjectStream）产生JasperPrint对象
                            jasperPrint = (JasperPrint) obj;

                        }
                        // 拦截出现空报表问题
                        if (jasperPrint != null
                                && jasperPrint.getPages().size() > 0) {
                            /**//*
                             * 调用JasperReport.jar中JasperViewer绘制报表Frame
                             * JasperViewer继承自JFrame，采用setDefaultCloseOperation响应关闭窗口事件
                             */

                            ViewerFrame viewerFrame = new ViewerFrame(this
                                    .getAppletContext(), jasperPrint,isShowPrintButton);
                            
                            viewerFrame.setVisible(true);
                            //viewerFrame.show();

                            // JasperViewer viewer = new
                            // JasperViewer(jasperPrint);
                            // viewer.setVisible(true);
                            // viewer.setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
                            // 如果请求为空弹出对话框予以提示
                        } else {
                            JOptionPane
                                    .showMessageDialog(this,
                                            "Please check Your Report SQL! It resulted in empty Report! ");
                            return;
                        }
                    }

其中requestUrl为applet配置中的REPORT_URL，现实中可以采用此种方式传递参数到applet中，下篇文章会介绍更合适的业务数据传递，?printView=true表示，传递printView参数对应的值为true，用来预览使用。剩下的工作就是怎么按照自己的要求打印和预览了。
 jasperReport为我们提供了打印和预览现成的方法：

// 打印报表
                                    JasperPrintManager
                                            .printReport(print, false);

/**//*  预览报表
                             * 调用JasperReport.jar中JasperViewer绘制报表Frame
                             * JasperViewer继承自JFrame，采用setDefaultCloseOperation响应关闭窗口事件
                             */
                            ViewerFrame viewerFrame = new ViewerFrame(this
                                    .getAppletContext(), jasperPrint);
                            viewerFrame.setVisible(true);

最后记着释放对象哦，浏览器会受不了得：

url = null;
            jasperPrint = null;

OK，客户端就出现了，参照demo没有什么难度，下一篇我会介绍一下具体的细节，及套打的实现。