Java web 中报表预览及打印

import java.io.ByteArrayOutputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.jasperreports.engine.JREmptyDataSource;
import net.sf.jasperreports.engine.JRExporterParameter;
import net.sf.jasperreports.engine.JRParameter;
import net.sf.jasperreports.engine.JasperFillManager;
import net.sf.jasperreports.engine.JasperPrint;
import net.sf.jasperreports.engine.JasperReport;
import net.sf.jasperreports.engine.export.JRPdfExporter;
import net.sf.jasperreports.engine.fill.JRFileVirtualizer;
import net.sf.jasperreports.engine.util.JRLoader;

public class ReportPrintUtil {

private JasperPrint getJasperPrint(JasperReport jReport, Map paramMap) {
        JasperPrint jPrint = null;
        try {
        // 填充报表数据
            jPrint = JasperFillManager.fillReport(jReport, paramMap, new JREmptyDataSource());
        } catch (Exception er) {
            er.printStackTrace();
        }
        return jPrint; 
    }

/**
* 支持多报表同时预览及打印
* @param request
* @param response
* @param url 报表存储(相对)路径
* @param paramMapList 报表参数值集合
*/
public void doPrint(HttpServletRequest request, HttpServletResponse response,String url, List paramMapList){
try{
List jasperPrintList = new ArrayList();
JasperReport jReport = (JasperReport) JRLoader.loadObject(getClass().getResource(url));
for (Iterator iter = paramMapList.iterator(); iter.hasNext();) {
Map paramMap = (Map) iter.next();
jasperPrintList.add(this.getJasperPrint(jReport, paramMap));
}

// 下面是在磁盘建立目录来优化内存
Map parameters = new HashMap();
        JRFileVirtualizer virtualizer = new JRFileVirtualizer(2);
        parameters.put(JRParameter.REPORT_VIRTUALIZER, virtualizer);
        // 填充完毕，锁住磁盘
        virtualizer.setReadOnly(true);
       
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        JRPdfExporter exporter = new JRPdfExporter();
       
        exporter.setParameter(JRExporterParameter.JASPER_PRINT_LIST, jasperPrintList);
        exporter.setParameter(JRExporterParameter.OUTPUT_STREAM, baos);
       
        exporter.exportReport();
        byte[] bytes = baos.toByteArray();
       
        // 设置报表以 pdf 格式输出
        response.setContentType("application/pdf");
        response.setContentLength(bytes.length + 10);
        ServletOutputStream ouputStream = response.getOutputStream();
        ouputStream.write(bytes, 0, bytes.length);
        ouputStream.flush();
        ouputStream.close();
}catch(Exception err){
err.printStackTrace();
}
}
}

(注:采用PDF格式打印时，需要安装相应的PDF阅读器才能进行预览。)