java sax动态生成xml，大量数据时、防止内存储器溢出

java sax动态生成xml，大量数据时、防止内存溢出

 

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.sax.SAXTransformerFactory;
import javax.xml.transform.sax.TransformerHandler;
import javax.xml.transform.stream.StreamResult;

import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;


import com.sbdcpn.upload.FtpClient;
import com.sbdcpn.utils.Log;

import com.sbdcpn.xmlparse.pagecfg.PageCfgXMLUtil;

public class BigDataWriteXmlBo {
	private final int  records = 1000;
	
	/**
	 * 将数据保存到xml上
	 * @throws ParserConfigurationException
	 * @throws IOException
	 * @throws TransformerException
	 * @throws SAXException 
	 * @throws InterruptedException 
	 */
	@SuppressWarnings({ "unchecked", "rawtypes" })
	public void generateXML() throws IOException, TransformerException, SAXException, InterruptedException{
		SAXTransformerFactory fac = (SAXTransformerFactory) SAXTransformerFactory.newInstance();
		TransformerHandler handler = fac.newTransformerHandler();
		Transformer transformer = handler.getTransformer();
		transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");//
		// 设置输出采用的编码方式
		transformer.setOutputProperty(OutputKeys.INDENT, "yes");// 是否自动添加额外的空白
		transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");// 是否忽略xml声明
		//文件名 ：前七位SWPM001为电文号+14位日期（年月日时分秒）
		StringBuffer fileName = new StringBuffer("SWPM001_");
		SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
		fileName.append(sdf.format(new Date())).append(".xml");	
		FileOutputStream fos = new FileOutputStream(fileName.toString());
		Result resultxml = new StreamResult(fos);
		handler.setResult(resultxml);
		//Message标签的属性
		AttributesImpl msgAtt = new AttributesImpl();
		msgAtt.addAttribute("", "", "MsgID", "", "SWPM001");
		msgAtt.addAttribute("", "", "ResourceID", "", "SW");
		handler.startDocument();
		handler.startElement("", "", "Message", msgAtt);		
		//空属性
		AttributesImpl fieldAtt = new AttributesImpl();
		//取得总记录数，进行分页处理
		long count = queryAllRows();
		long page = count / records;
		if (count % records != 0) {
			page = page + 1;
		}
		String four = "\n    ";
		String eight = "\n        ";
		//开始行号，结束行号
		long start = 1, end = records;	
		//根据页数进行循环
		for (long j = 1; j <= page; j++) {
			// 分页取得目录数据
			List<Map> data = this.queryStockInventory(start, end);
			//按行循环一页中的数据
			for (int i = 0; i < data.size(); i++) {
				handler.characters(four.toCharArray(), 0, four.length());//行缩进
				Map<String, String> rec = data.get(i);
				//行结点属性
				AttributesImpl dataRowAtt = new AttributesImpl();
				dataRowAtt.addAttribute("", "", "id", "", String.valueOf(start - 1 + i));
				// 行结点
				handler.startElement("", "", "DataRow", dataRowAtt);
				rec.remove("row_num");
				Iterator it = rec.entrySet().iterator();
				//按列循环生成数据结点
				while (it.hasNext()) {
					handler.characters(eight.toCharArray(), 0, eight.length());// 列缩进
					Map.Entry<String, String> entry = (Map.Entry<String, String>) it.next();
					String key = entry.getKey();
					String value = entry.getValue();
					// 用字段名作为标签名,对应的数据作为内容
					handler.startElement("", "", key, fieldAtt);
					handler.characters(value.toCharArray(), 0, value.length());
					handler.endElement("", "", key);					
				}
				handler.characters(four.toCharArray(), 0, four.length());//行缩进
				handler.endElement("", "", "DataRow");
			}
			start = end + 1;
			end = end + records;
			handler.endDocument();// 文档结束,同步到磁盘
			handler.startDocument();
		}
		handler.endElement("", "", "Message");
		handler.endDocument();
		fos.close();//不关闭的话，后面删除不了文件
		uploadFile(fileName.toString());// 上传文件至ftp
	}
	
	/**
	 * 把生成出来的文件，上传到ftp；上传失败后，1分钟后再次尝试上传，连续三次不成功便停止
	 * @param fileName 文件名
	 * @param filePath 路径
	 * @throws InterruptedException 
	 */
	private void uploadFile(String fileName) throws InterruptedException {
		String[] path = PageCfgXMLUtil.getInstance().getPageConstByKey("stockFtpXmlPath").split(" ");
		int reSend = 1;
		//上传失败时，1分钟后再次尝试
		while (reSend <= 3) {
			FtpClient ftp = new FtpClient();
			ftp.Connect(path[0], Integer.parseInt(path[1]));// ip与端口
			ftp.Login(path[3], path[4]);// 用户名与密码
			ftp.SetCurDir(path[2]);// 目录
			boolean isUpload = ftp.PutFile(fileName, fileName);
			ftp.DisConnect();
			if (isUpload) {
				_log.showLog(fileName + "成功上传到FTP服务器上！");
				break;
			} else {
				_log.showLog(fileName + "尝试" + reSend + "次后，上传到FTP服务器失败！");
				reSend++;
				Thread.sleep(60000);				
			}
		}
		File file = new File(fileName);
		String flag = file.delete() ? "成功！" : "失败！";
		_log.showLog("删除临时文件：" + fileName + flag);
	}
	
	/**
	 * 分页查询，示例查询，假设数据有十万条
	 * @return
	 */
	@SuppressWarnings("rawtypes")
	private List queryStockInventory(long start, long end) {
		StringBuffer insertInto = new StringBuffer();	
		insertInto.append(" SELECT")
				.append(" tmp_stock_inv.*")
				.append(" FROM(")
				.append(" SELECT *,")				
				.append("rownum row_num")
				.append(" FROM table")
				.append(" WHERE rownum <=").append(end)
				.append(") tmp_stock_inv")
				.append(" WHERE")
				.append(" tmp_stock_inv.row_num >=").append(start);
		_log.showLog("查询：" + insertInto.toString());
		return _dao.query(insertInto.toString());
	}
	
	/**
	 * 取得总记录数
	 * @return
	 */
	@SuppressWarnings("unchecked")
	private int queryAllRows() {
		StringBuffer insertInto = new StringBuffer();	
		insertInto.append("SELECT count(*) rows_count FROM stock_inventory WHERE stock_qty > 0");
		_log.showLog("查询总记录数：" + insertInto.toString());
		Map<String,String> rs = (Map<String,String>)_dao.queryOneRow(insertInto.toString());
		return Integer.parseInt(rs.get("rows_count"));
	}
}