以流的形式直接导出 csv文件

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.beanutils.BeanUtils;
import org.zkoss.io.FileWriter;
import org.zkoss.zul.Filedownload;


public class ExportCSV {

	@SuppressWarnings("rawtypes")
	public static File createCSVFile(List> exportData, Map rowMapper,String filename) {
		StringWriter stringWriter = new StringWriter();
		BufferedWriter csvFileOutputStream = null;
		StringBuffer b = null;
		try {
			 b = new StringBuffer();
			// GB2312使正确读取分隔符","
			csvFileOutputStream = new BufferedWriter(stringWriter);
			// 写入文件头部
			for (Iterator propertyIterator = rowMapper.entrySet().iterator(); propertyIterator.hasNext();) {
				java.util.Map.Entry propertyEntry = (java.util.Map.Entry) propertyIterator.next();
				csvFileOutputStream.write("\""+ String.valueOf(propertyEntry.getValue().toString()) + "\"");
				if (propertyIterator.hasNext()) {
					csvFileOutputStream.write(",");
				}
			}    
			csvFileOutputStream.newLine();

			// 写入文件内容
			for (Iterator iterator = exportData.iterator(); iterator.hasNext();) {
				Object row = (Object) iterator.next();

				for (Iterator propertyIterator = rowMapper.entrySet().iterator(); propertyIterator.hasNext();) {
					java.util.Map.Entry propertyEntry = (java.util.Map.Entry) propertyIterator.next();
					
					String str="	"+String.valueOf(BeanUtils.getProperty(row, propertyEntry.getKey().toString()));
					
					csvFileOutputStream.write("\""+ str + "\"");
					
					System.out.println("每列：："+ ""+String.valueOf(BeanUtils.getProperty(row, propertyEntry.getKey().toString()))); 
					if (propertyIterator.hasNext()) {  
						csvFileOutputStream.write(",");
					}
				}    
				System.out.println("换行：：：：：：：：：：：：：：：：：：：：：：：：：：：：：：：：：：：");
				if (iterator.hasNext()) { 
					csvFileOutputStream.newLine();
				}
			}
			csvFileOutputStream.flush();
			try {
				Filedownload s = new Filedownload();
				String str = stringWriter.getBuffer().toString();
			    s.save(str.getBytes("GB2312"), "application/octet-stream;charset=GB2312", filename);
			} catch (Exception e1) {
				e1.printStackTrace();
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				csvFileOutputStream.close();
				stringWriter.close();
				
			} catch (IOException e) {
				e.printStackTrace(); 
			}
		}    
		return null;
	}
	public  static void down()
	{
		List> exportData = new ArrayList>();
		Map row1 = new HashMap();
		row1 = new LinkedHashMap();
		row1.put("1", "21");
		row1.put("2", "22");
		row1.put("3", "23");
		row1.put("4", "24");
		exportData.add(row1);
		
		Map map = new HashMap();
		map.put("1", "第一列");
		map.put("2", "第二列");
		map.put("3", "第三列");
		map.put("4", "第四列");
		ExportCSV.createCSVFile(exportData, map,  "abc.csv");
	}
}