package common.DaoImplement;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;import common.DaoInterface.IConnectionDatabase;
import common.tool.ReaderXmlConfig;public class ConDatabaseBySqlServerImp implements IConnectionDatabase
{private String driver;private String url;private String username;private String password;private Connection con = null;private Statement st = null;ResultSet rs  = null;/*** 通过读取配置文件初始化参数* ReaderXmlConfig,这是一个单例的类，用于得到Config.xml配置文件*/public void initialize(){Document doc = ReaderXmlConfig.getInstance();NodeList dbs = doc.getElementsByTagName("db");Element db = (Element)dbs.item(0);String driver = db.getElementsByTagName("driver").item(0).getFirstChild().getNodeValue();String url = db.getElementsByTagName("url").item(0).getFirstChild().getNodeValue();String username = db.getElementsByTagName("username").item(0).getFirstChild().getNodeValue();String password = db.getElementsByTagName("password").item(0).getFirstChild().getNodeValue();this.driver = driver;this.url = url;this.username = username;this.password = password;}/*** 构造方法* 加载数据库*/public ConDatabaseBySqlServerImp(){initialize();try {Class.forName(driver);} catch (ClassNotFoundException e) {e.printStackTrace();}}/***对外提高Connection的接口*在此没有直接使用上面定义的con，而是重新定义了一个conn，即每次外部调用getConnection()方法，都将返回一个新的连接（注意在使用后关闭）*若此处直接是使用con，可能导致多线程并发访问，导致出错。*/@Overridepublic  Connection getConnection() {Connection conn = null;try {conn = DriverManager.getConnection(url, username, password);} catch (SQLException e) {e.printStackTrace();}return conn;}/*** 用于内部的使用*/private void getCon(){if(con == null){try {con = DriverManager.getConnection(url, username, password);} catch (SQLException e) {e.printStackTrace();}}}/*** 执行查询*/@Overridepublic ResultSet executeSql(String sql) {getCon();try {st = con.createStatement();rs = st.executeQuery(sql);} catch (SQLException e) {e.printStackTrace();}return rs;}/*** 执行删除，修改等无返回值的语句*/@Overridepublic Boolean executeUpdate(String sql) {getCon();try {st = con.createStatement();st.executeUpdate(sql);            } catch (SQLException e) {e.printStackTrace();return false;}return true;}/*** 关闭连接*/@Overridepublic void closeConnection() {try{if(rs != null){rs.close();rs = null;}if(st != null){st.close();st = null;}if(con != null){con.close();con = null;}}catch(SQLException e){e.printStackTrace();}}}