java sax动态生成xml，大量数据时、防止内存溢出
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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"));}}