JDBC从入门到放弃-01:JDBC连接创建以及优化从配置文件获取jdbc连接参数

JDBC从入门到放弃

JDBC（Java Database Connectivity）

在Java中，与数据库进行交互的技术可以分成这么几类：

①JDBC直接访问数据库

②JDO技术，也是一个用于存取数据库中的对象的标准化API

③第三方框架工具，如Hibernate，Mybatis等，但是Hibernate，Mybatis这些框架的底层也是用的JDBC，只是对JDBC进行了二次封装！

JDBC API是一系列的接口，它能使得应用程序能够进行数据库连接，执行SQL语句，并且获取到数据库返回的结果！

JDBC连接创建

1：新建JavaWeb maven项目

2：增加依赖

<dependency>                <groupId>mysqlgroupId>                <artifactId>mysql-connector-javaartifactId>                <version>5.1.47version>           dependency>

3：准备数据

4：编写数据库链接程序

package com.liujia.jdbc;   import java.sql.Connection; import java.sql.SQLException; import java.util.Properties;   import com.mysql.jdbc.Driver;   /**  * 数据库工具类  *  * @author liujia  *  */ public class DBUtils {        private DBUtils() {      };        private static DBUtils instance;        public static DBUtils getInstance() {           if (instance == null) {                instance = new DBUtils();           }           return instance;      }        public Connection getConnection() {           Connection connection = null;           try {                Driver driver = new com.mysql.jdbc.Driver();                String url = "jdbc:mysql://127.0.0.1:3306/study";                Properties info = new Properties();                info.setProperty("user", "root");                info.setProperty("password", "123456");                connection = driver.connect(url, info);           } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();           }           return connection;      } }

5：测试

优化之配置文件方式

这样创建数据库连接的方式采用硬编码的方法，将数据库驱动，url，用户名和密码等都写死在程序代码中，一旦项目发布，修改数据库以及用户名密码都需要在代码中进行编码，灵活性很差。

因此，现在需要将其进行优化，将其放置于配置文件中。

增加配置文件

db.driverClass=com.mysql.jdbc.Driver db.url=jdbc:mysql://127.0.0.1:3306/study db.user=root db.password=123456

修改代码

package com.liujia.db.jdbc;   import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.Driver; import java.sql.SQLException; import java.util.Properties;   /**  *  * @author liujia  *  */ public class DBUtils {        private DBUtils() {      };        private static DBUtils instance;        public static DBUtils getInstance() {           if (instance == null) {                instance = new DBUtils();           }           return instance;      }        /**       * 获取数据库连接       *       * @return       */      public Connection getConnection() {           Connection connection = null;           InputStream in = null;           try {                Driver driver;                in = getClass().getClassLoader().getResourceAsStream("db.properties");                Properties properties = new Properties();                properties.load(in);                  String driverClass = properties.getProperty("db.driverClass");                String url = properties.getProperty("db.url");                String user = properties.getProperty("db.user");                String password = properties.getProperty("db.password");                  driver = (Driver) Class.forName(driverClass).newInstance();                Properties info = new Properties();                info.setProperty("user", user);                info.setProperty("password", password);                connection = driver.connect(url, info);           } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();           } catch (InstantiationException e) {                // TODO Auto-generated catch block                e.printStackTrace();           } catch (IllegalAccessException e) {                // TODO Auto-generated catch block                e.printStackTrace();           } catch (ClassNotFoundException e) {                // TODO Auto-generated catch block                e.printStackTrace();           } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();           } finally {                if (in != null) {                     try {                          in.close();                     } catch (IOException e) {                          // TODO Auto-generated catch block                          e.printStackTrace();                     }                }           }           return connection;      }        /**       * 关闭数据库连接       *       * @param con       */      public static void closeCon(Connection con) {           if (con != null) {                try {                     con.close();                } catch (SQLException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();                }           }      } }

编写测试程序

<%@page import="com.liujia.db.jdbc.DBUtils"%> <%@page import="java.sql.Connection"%> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>你好title> head> <body> <h1>测试服务器是否可用h1> <% Connection con = DBUtils.getInstance().getConnection();%> <%=con %> body> html>

进一步优化之使用Drivermanager

我们在项目中一般不直接使用Driver接口而是使用Drivermaager来创建数据库连接。

package com.liujia.db.jdbc;   import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.util.Properties;   /**  *  * @author liujia  *  */ public class DBUtils {        private DBUtils() {      };        private static DBUtils instance;        public static DBUtils getInstance() {           if (instance == null) {                instance = new DBUtils();           }           return instance;      }        /**       *       * 创建数据库连接       * @return       */      public Connection getConnection() {           Connection connection = null;           InputStream in = null;           try {                in = getClass().getClassLoader().getResourceAsStream("db.properties");                               Properties properties = new Properties();                properties.load(in);                String driverClass = properties.getProperty("db.driverClass");                String url = properties.getProperty("db.url");                String user = properties.getProperty("db.user");                String password = properties.getProperty("db.password");                               //加载数据库驱动                Class.forName(driverClass);                //使用DriverManager创建数据库连接                connection =DriverManager.getConnection(url, user, password);           } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();           }  catch (ClassNotFoundException e) {                // TODO Auto-generated catch block                e.printStackTrace();           } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();           } finally {                if (in != null) {                     try {                          in.close();                     } catch (IOException e) {                          // TODO Auto-generated catch block                          e.printStackTrace();                     }                }           }           return connection;      }        /**       * 关闭数据库连接       *       * @param con       */      public static void closeCon(Connection con) {           if (con != null) {                try {                     con.close();                } catch (SQLException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();                }           }      } }

源码下载地址如下

https://download.csdn.net/download/caoshangfeidie000/10677277