使用iReport导出Excel：关键代码解析

import java.io.File;  
import java.io.FileInputStream;  
import java.io.FileNotFoundException;  
import java.io.IOException;  
import java.io.InputStream;  
import java.lang.reflect.Field;  
import java.util.Collection;  
import java.util.HashMap;  
import java.util.List;  
import java.util.Map;  
  
import javax.servlet.ServletOutputStream;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
  
import org.apache.log4j.Logger;  
import org.apache.struts2.ServletActionContext;  
import org.jfree.util.Log;  
  
import com.opensymphony.xwork2.ActionContext;  
import com.qqw.crm.common.dao.impl.BaseDaoImpl;  
  
import net.sf.jasperreports.engine.JRDataSource;  
import net.sf.jasperreports.engine.JRException;  
import net.sf.jasperreports.engine.JRExporter;  
import net.sf.jasperreports.engine.JRExporterParameter;  
import net.sf.jasperreports.engine.JasperExportManager;  
import net.sf.jasperreports.engine.JasperFillManager;  
import net.sf.jasperreports.engine.JasperPrint;  
import net.sf.jasperreports.engine.JasperReport;  

import net.sf.jasperreports.engine.base.JRBaseReport;  
import net.sf.jasperreports.engine.data.JRBeanCollectionDataSource;  
import net.sf.jasperreports.engine.export.JRHtmlExporter;  
import net.sf.jasperreports.engine.export.JRHtmlExporterParameter;  
import net.sf.jasperreports.engine.export.JRRtfExporter;  
import net.sf.jasperreports.engine.export.JRXlsExporter;  
import net.sf.jasperreports.engine.export.JRXlsExporterParameter;  
import net.sf.jasperreports.engine.util.JRLoader;  
  
public class JasperHelper {  
    private static Logger logger = Logger.getLogger(JasperHelper.class);  
       public static final String PRINT_TYPE = "print";  
       public static final String PDF_TYPE = "pdf";  
       public static final String EXCEL_TYPE = "excel";  
       public static final String HTML_TYPE = "html";  
       public static final String WORD_TYPE = "word";  
     public static void prepareReport(JasperReport jasperReport, String type) {  
         logger.debug("The method======= prepareReport() start.......................");  
            /* 
             * 如果导出的是excel，则需要去掉周围的margin 
             */  
            if ("excel".equals(type))  
             try {  
              Field margin = JRBaseReport.class  
                .getDeclaredField("leftMargin");  
              margin.setAccessible(true);  
              margin.setInt(jasperReport, 0);  
              margin = JRBaseReport.class.getDeclaredField("topMargin");  
              margin.setAccessible(true);  
              margin.setInt(jasperReport, 0);