模仿mongodb采用xml+json实现小型数据库

mini-mongodb

   模仿mongodb采用Xml+json实现小型数据库;
    1.实现数据库创建
    2.表的创建
    3.表数据的增、删、改、查

    供大家参考学习使用，有助于更好的了解MongoDB的实现原理！

代码下载地址： http://zhangdaiscott.github.io/mini-mogodb

   package org.jeecgframework;


import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;


import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
import org.jdom.output.XMLOutputter;


import com.google.gson.Gson;


public class MiniMogodb {
 private static final String _uuid = "_uuid";


 /**
  * 获取表的全部数据
  * 
  * @param path
  * @param tablename
  * @return
  * @throws Exception
  */
 public List<Map> loadTableDatas(String path, String tablename) throws Exception {
 Gson gson = new Gson();
 FileInputStream file = new FileInputStream(path);
 SAXBuilder saxBuilder = new SAXBuilder();
 Document document = saxBuilder.build(file);
 Element root = document.getRootElement();


 List<Map> l = new ArrayList();
 List<Element> list = root.getChildren();
 for (Element x : list) {
 if (x.getAttributeValue("name").equals(tablename)) {
 List<Element> al = x.getChildren();
 for (Element s : al) {
 String data = s.getText();
 if (data == null) {
 break;
 }
 Map mp = gson.fromJson(data, Map.class);
 l.add(mp);
 }
 }
 }
 return l;
 }


 /**
  * 表插入数据
  * 
  * @param path
  * @param tablename
  * @param po
  * @return
  * @throws JDOMException
  * @throws IOException
  */
 public boolean addData(String path, String tablename, Object po)
 throws JDOMException, IOException {
 Gson gson = new Gson();
 boolean flag = false;
 FileInputStream file = new FileInputStream(path);
 SAXBuilder saxBuilder = new SAXBuilder();
 Document document = saxBuilder.build(file);
 Element root = document.getRootElement();


 List<Element> list = root.getChildren();
 for (Element x : list) {
 if (x.getAttributeValue("name").equals(tablename)) {
 Map base = new HashMap();
 base.put(_uuid, UUID.randomUUID().toString());
 Element data = new Element("data");
 String json = gson.toJson(po);
 Map mp = gson.fromJson(json, Map.class);
 base.putAll(mp);
 data.addContent(gson.toJson(base));
 x.addContent(data);
 }
 }
 XMLOutputter out = new XMLOutputter();
 out.output(document, new FileOutputStream(path));
 flag = true;
 System.out
 .println("----------insert --- data --- success----------------------");
 return flag;
 }


 /**
  * 表修改数据
  * 
  * @param path
  * @param tablename
  * @param po
  * @throws JDOMException
  * @throws IOException
  */
 public void updateData(String path, String tablename, Object po)
 throws JDOMException, IOException {
 FileInputStream file = new FileInputStream(path);
 SAXBuilder saxBuilder = new SAXBuilder();
 Document document = saxBuilder.build(file);
 Element root = document.getRootElement();
 Gson gson = new Gson();


 List<Element> list = root.getChildren();
 for (Element x : list) {
 if (x.getAttributeValue("name").equals(tablename)) {
 List<Element> al = x.getChildren();
 for (Element s : al) {
 // 如果定位Data[通过UUID唯一标示]
 Map mp = gson.fromJson(s.getText(), Map.class);
 Map newmp = gson.fromJson(gson.toJson(po), Map.class);
 if (mp.get(_uuid).equals(newmp.get(_uuid))) {
 mp.putAll(newmp);
 Element data = new Element("data");
 data.setText(gson.toJson(mp));
 x.removeContent(s);
 x.addContent(data);
 break;
 }
 }
 }
 }
 XMLOutputter out = new XMLOutputter();
 out.output(document, new FileOutputStream(path));
 System.out
 .println("----------update --- data --- success----------------------");
 }


 /**
  * 表删除数据
  * 
  * @param path
  * @param tablename
  * @param po
  * @throws JDOMException
  * @throws IOException
  */
 public void deleteData(String path, String tablename, Object po)
 throws JDOMException, IOException {
 FileInputStream file = new FileInputStream(path);
 Gson gson = new Gson();
 SAXBuilder saxBuilder = new SAXBuilder();
 Document document = saxBuilder.build(file);
 Element root = document.getRootElement();
 List<Element> list = root.getChildren();
 for (Element x : list) {
 List<Element> al = x.getChildren();
 if (x.getAttributeValue("name").equals(tablename)) {
 for (Element s : al) {
 // 如果定位Data[通过UUID唯一标示]
 Map mp = gson.fromJson(s.getText(), Map.class);
 Map newmp = gson.fromJson(gson.toJson(po), Map.class);
 if (mp.get(_uuid).equals(newmp.get(_uuid))) {
 x.removeContent(s);
 break;
 }
 }
 }
 }
 XMLOutputter out = new XMLOutputter();
 out.output(document, new FileOutputStream(path));
 System.out
 .println("----------delete --- data --- success----------------------");
 }


 /**
  * 创建数据库
  * 
  * @param path
  * @throws Exception
  */
 public void createDataBase(String path) throws Exception {
 FileOutputStream file1 = new FileOutputStream(path);
 Document document = new Document();
 Element root = new Element("database");
 Element sort1 = new Element("table");
 sort1.setAttribute("name", "test");
 Element sort2 = new Element("table");
 sort2.setAttribute("name", "system.indexs");
 Element sort3 = new Element("table");
 sort3.setAttribute("name", "system.users");


 root.addContent(sort1);
 root.addContent(sort2);
 root.addContent(sort3);


 document.setRootElement(root);
 XMLOutputter out = new XMLOutputter();
 out.output(document, file1);
 System.out
 .println("----------create---database---success-------------------");
 }
}

<?xml version="1.0" encoding="UTF-8"?>
<database>
 <table name="test">
 <data>{"sex":"男","age":20.0,"name":"lisan","money":2000.98,"_uuid":"a2b64d1a-63ea-4a1b-b1e3-67adcc687c0a"}
 </data>
 </table>
 <table name="system.indexs" />
 <table name="system.users" />
</database>

   * 作者：     张代浩
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