java 优化 笔记

由于项目的数据是定时更新，为了页面的加载速度变快，使用了各种的优化：

1.首先是数据库的优化，由于数据是属于每分钟一条的，经过和项目经理的协商，可以计算为5分钟一天（取平均数），然后把一天分为288列(每天产生一天数据:ps 相当于java的去除冗余，而不是把全部的都简化到一条数据了，要看真正的需求）；

2.后来由于上面的人数页面加载还是慢，而且由于每次访问数据库操作量大，有需要进一步的优化，利用ehcache缓存，把数据存到内存中，然后定时更新，具体就不写ehcache怎么使用，毕竟不是为了写这个

ps:2.1.中间还有一些优化就简单的说一下不仔细说了。尽可能优化sql语句，能一次查完的数据，不要分多次查询，能使用更有效率的sql语句就不用其他的等。合理利用多线程。

3.再后来，由于数据量的增加，服务器内存有限（小公司 ~ ~!）,经过商量决定利用静态页面，然后由我来做，关于页面静态化请点击。由于第一次做页面静态化所以没有考虑更多就开始去做，后来发现页面内有页面加载的时候就会去做一个post请求，不知道怎么实现怎么加载到页面中。最后放弃页面静态化，至于为什么不把post请求改为直接传到页面，是因为改动太大而且有更好的选择。

4.更好的选择就是把数据写到xml中，用的时候从xml中读取。定时去更新xml中的数据。下面把 自己写的一个简单的创建和解析xml的代码贴一下，没怎么用过，写的不好的地方还请指出来，互相学习。

package com.intcache.hepburn.util;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.PrintWriter;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.ParserConfigurationException;import javax.xml.transform.OutputKeys;import javax.xml.transform.Transformer;import javax.xml.transform.TransformerConfigurationException;import javax.xml.transform.TransformerException;import javax.xml.transform.TransformerFactory;import javax.xml.transform.dom.DOMSource;import javax.xml.transform.stream.StreamResult;import org.w3c.dom.Document;import org.w3c.dom.Element;import org.w3c.dom.Node;import org.w3c.dom.NodeList;import org.xml.sax.SAXException;import com.intcache.base.var.Constants;public class ParseXml {private static Document document;private static String ONE_ELEMENT_NAME = "oneData";private static String TWO_ELEMENT_NAME = "twoData";private static String THREE_ELEMENT_NAME = "threeData";private static String FOUR_ELEMENT_NAME = "fourData";private static String FIVE_ELEMENT_NAME = "fiveData";private static String SIX_ELEMENT_NAME = "sixData";private static String SEVEN_ELEMENT_NAME = "sevenMap";public static void init() {try {DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder builder = factory.newDocumentBuilder();document = builder.newDocument();} catch (ParserConfigurationException e) {System.out.println(e.getMessage());}}public static String getNodeName(String nodeName) {return Constants.XML_NODE_PREFIX + nodeName;}/** * 生成一个xml 解析的时候 参数map 和此方法一致 * @param fileName 文件名 * @param oneMap 第一个map Map<String,List<Long>> * @param twoMap 第二个map Map<String,List<Long>> * @param threeMap 第三个map Map<String, Long> * @param fourMap 第四个map Map<String, Long> * @param fiveMap 第五个map Map<String, List<Double>> * @param sixMap 第六个map Map<String, List<Double>> * @param sevenMap 第七个map Map<String, Map<String, List<Float>>> */public static void createXml(String fileName, Map<String, List<Long>> oneMap, Map<String, List<Long>> twoMap, Map<String, Long> threeMap, Map<String, Long> fourMap,Map<String, List<Double>> fiveMap, Map<String, List<Double>> sixMap, Map<String, Map<String, List<Float>>> sevenMap) {init();Element root = document.createElement(getNodeName("data")); //创建根节点  document.appendChild(root);if (oneMap != null) {Element oneItem = document.createElement(ONE_ELEMENT_NAME);root.appendChild(oneItem);for (String str : oneMap.keySet()) {addElement(oneMap.get(str).toString(), oneItem, str);}}if (twoMap != null) {Element twoItem = document.createElement(TWO_ELEMENT_NAME);root.appendChild(twoItem);for (String str : twoMap.keySet()) {addElement(twoMap.get(str).toString(), twoItem, str);}}if (threeMap != null) {Element threeItem = document.createElement(THREE_ELEMENT_NAME);root.appendChild(threeItem);for (String str : threeMap.keySet()) {addElement(threeMap.get(str).toString(), threeItem, str);}}if (fourMap != null) {Element fourItem = document.createElement(FOUR_ELEMENT_NAME);root.appendChild(fourItem);for (String str : fourMap.keySet()) {addElement(fourMap.get(str).toString(), fourItem, str);}}if (fiveMap != null) {Element fiveItem = document.createElement(FIVE_ELEMENT_NAME);root.appendChild(fiveItem);for (String str : fiveMap.keySet()) {addElement(fiveMap.get(str).toString(), fiveItem, str);}}if (sixMap != null) {Element sixItem = document.createElement(SIX_ELEMENT_NAME);root.appendChild(sixItem);for (String str : sixMap.keySet()) {addElement(sixMap.get(str).toString(), sixItem, str);}}if (sevenMap != null) {Element sevenItem = document.createElement(SEVEN_ELEMENT_NAME);root.appendChild(sevenItem);for (String str : sevenMap.keySet()) {Element strItem = document.createElement(str);sevenItem.appendChild(strItem);for (String str2 : sevenMap.get(str).keySet()) {addElement(sevenMap.get(str).get(str2).toString(), strItem, str2);}}}TransformerFactory tf = TransformerFactory.newInstance();try {Transformer transformer = tf.newTransformer();DOMSource source = new DOMSource(document);transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8");transformer.setOutputProperty(OutputKeys.INDENT, "yes");PrintWriter pw = new PrintWriter(new FileOutputStream(fileName));StreamResult result = new StreamResult(pw);transformer.transform(source, result); //关键转换  System.out.println("生成XML文件成功!");} catch (TransformerConfigurationException e) {System.out.println(e.getMessage());} catch (IllegalArgumentException e) {System.out.println(e.getMessage());} catch (FileNotFoundException e) {System.out.println(e.getMessage());} catch (TransformerException e) {System.out.println(e.getMessage());}}private static void addElement(String textContent, Element parentItem, String str) {Element item = document.createElement(getNodeName(str));item.setTextContent(textContent);parentItem.appendChild(item);}public static void createXml(String fileName) {init();Element root = document.createElement("data"); //创建根节点  document.appendChild(root);Element data = document.createElement("wk");data.setNodeValue("NodeValue");data.setTextContent("TextContent");root.appendChild(data);TransformerFactory tf = TransformerFactory.newInstance();try {Transformer transformer = tf.newTransformer();DOMSource source = new DOMSource(document);transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8");transformer.setOutputProperty(OutputKeys.INDENT, "yes");PrintWriter pw = new PrintWriter(new FileOutputStream(fileName));StreamResult result = new StreamResult(pw);transformer.transform(source, result); //关键转换  System.out.println("生成XML文件成功!");} catch (TransformerConfigurationException e) {System.out.println(e.getMessage());} catch (IllegalArgumentException e) {System.out.println(e.getMessage());} catch (FileNotFoundException e) {System.out.println(e.getMessage());} catch (TransformerException e) {System.out.println(e.getMessage());}}/** * 解析xml文件  解析的时候 参数map 和生成xml（createXml()）一致 * @param fileName 文件名 * @param oneMap 第一个map Map<String,List<Long>> * @param twoMap 第二个map Map<String,List<Long>> * @param threeMap 第三个map Map<String, Long> * @param fourMap 第四个map Map<String, Long> * @param fiveMap 第五个map Map<String, List<Double>> * @param sixMap 第六个map Map<String, List<Double>> * @param sevenMap 第七个map Map<String, Map<String, List<Float>>> */public static void parserXml(String fileName, Map<String, List<Long>> oneMap, Map<String, List<Long>> twoMap, Map<String, Long> threeMap, Map<String, Long> fourMap,Map<String, List<Double>> fiveMap, Map<String, List<Double>> sixMap, Map<String, Map<String, List<Float>>> sevenMap) {try {DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();DocumentBuilder db = dbf.newDocumentBuilder();Document document = db.parse(fileName);NodeList employees = document.getChildNodes();String[] strArr;List<Long> dataList;for (int i = 0; i < employees.getLength(); i++) {Node employee = employees.item(i);NodeList employeeInfo = employee.getChildNodes();for (int j = 0; j < employeeInfo.getLength(); j++) {Node node = employeeInfo.item(j);NodeList employeeMeta = node.getChildNodes();for (int k = 0; k < employeeMeta.getLength(); k++) {if (employeeInfo.item(j).getNodeName().equals(ONE_ELEMENT_NAME)) {strArr = employeeMeta.item(k).getTextContent().replace("[", "").replace("]", "").split(",");dataList = new ArrayList<Long>();if (employeeMeta.item(k).getNodeName().contains("#text")) {continue;}for (String string : strArr) {if (string.trim().equals("")) {dataList.add(Long.valueOf(0));} else {dataList.add(Long.valueOf(string.trim()));}}oneMap.put(employeeMeta.item(k).getNodeName().replace(Constants.XML_NODE_PREFIX, ""), dataList);} else if (employeeInfo.item(j).getNodeName().equals(TWO_ELEMENT_NAME)) {strArr = employeeMeta.item(k).getTextContent().replace("[", "").replace("]", "").split(",");dataList = new ArrayList<Long>();if (employeeMeta.item(k).getNodeName().contains("#text")) {continue;}for (String string : strArr) {if (string.trim().equals("")) {dataList.add(Long.valueOf(0));} else {dataList.add(Long.valueOf(string.trim()));}}twoMap.put(employeeMeta.item(k).getNodeName().replace(Constants.XML_NODE_PREFIX, ""), dataList);} else if (employeeInfo.item(j).getNodeName().equals(THREE_ELEMENT_NAME)) {threeMap.put(employeeMeta.item(k).getNodeName().replace(Constants.XML_NODE_PREFIX, ""),Long.valueOf((employeeMeta.item(k).getTextContent().trim().equals("") ? String.valueOf(0) : employeeMeta.item(k).getTextContent().toString())));} else if (employeeInfo.item(j).getNodeName().equals(FOUR_ELEMENT_NAME)) {fourMap.put(employeeMeta.item(k).getNodeName().replace(Constants.XML_NODE_PREFIX, ""),Long.valueOf((String) (employeeMeta.item(k).getTextContent().trim().equals("") ? String.valueOf(0) : employeeMeta.item(k).getTextContent().toString())));} else if (employeeInfo.item(j).getNodeName().equals(FIVE_ELEMENT_NAME)) {strArr = employeeMeta.item(k).getTextContent().replace("[", "").replace("]", "").split(",");List<Double> doubleList = new ArrayList<Double>();if (employeeMeta.item(k).getNodeName().contains("#text")) {continue;}for (String string : strArr) {if (string.trim().equals("")) {doubleList.add(Double.valueOf(0));} else {doubleList.add(Double.valueOf(string.trim()));}}fiveMap.put(employeeMeta.item(k).getNodeName().replace(Constants.XML_NODE_PREFIX, ""), doubleList);} else if (employeeInfo.item(j).getNodeName().equals(SIX_ELEMENT_NAME)) {strArr = employeeMeta.item(k).getTextContent().replace("[", "").replace("]", "").split(",");List<Double> doubleList = new ArrayList<Double>();if (employeeMeta.item(k).getNodeName().contains("#text")) {continue;}for (String string : strArr) {if (string.trim().equals("")) {doubleList.add(Double.valueOf(0));} else {doubleList.add(Double.valueOf(string.trim()));}}sixMap.put(employeeMeta.item(k).getNodeName().replace(Constants.XML_NODE_PREFIX, ""), doubleList);} else if (employeeInfo.item(j).getNodeName().equals(SEVEN_ELEMENT_NAME)) {Map<String, List<Float>> map = new HashMap<String, List<Float>>();Node floatData = employeeMeta.item(k);NodeList floatDatas = floatData.getChildNodes();for (int l = 0; l < floatDatas.getLength(); l++) {strArr = floatDatas.item(l).getTextContent().replace("[", "").replace("]", "").split(",");List<Float> floatList = new ArrayList<Float>();if (floatDatas.item(l).getNodeName().contains("#text")) {continue;}for (String string : strArr) {if (string.trim().equals("")) {floatList.add(Float.valueOf(0));} else {floatList.add(Float.valueOf(string.trim()));}}map.put(floatDatas.item(l).getNodeName().replace(Constants.XML_NODE_PREFIX, ""), floatList);}sevenMap.put(employeeMeta.item(k).getNodeName(), map);}}}}System.out.println("解析完毕");} catch (FileNotFoundException e) {System.out.println(e.getMessage());} catch (ParserConfigurationException e) {System.out.println(e.getMessage());} catch (SAXException e) {System.out.println(e.getMessage());} catch (IOException e) {System.out.println(e.getMessage());}}public static void main(String[] args) {createXml("D:\\wk.txt");}}

代码是死的，人是活的，根据需求自己改。

好久没有写过原创的了，好激动撒

还有什么方法可以优化的还请指教，（当然有很多啦，本人刚入行 勿喷撒）