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
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<!-- MySql --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.47</version> </dependency> |
3：准备数据
4：编写数据库链接程序
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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
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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
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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(); } } } }
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编写测试程序
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<%@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。
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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(); } } } }
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源码下载地址如下
https://download.csdn.net/download/caoshangfeidie000/10677277