基本概念

  1.   - 概念：其实就是一个容器（集合），存放数据库连接的容器
  2.         - 当系统初始化好后，容器被创建，容器中会申请一些连接对象，当用户来访问数据库时，从容器中获取连接对象，用户访问完之后，会将连接对象归还给容器。
  3.   - 好处：
  4.         - 节约资源
  5.         - 用户访问高效
  6.   - 实现：
  7.         - 标准接口：DateSource  javax.sql包下的
  8.               - 方法<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582206944560-ee8ecd38-a6b1-4703-b4b5-5bbf8d3e8a94.png#align=left&display=inline&height=99&name=image.png&originHeight=99&originWidth=435&size=82339&status=done&style=none&width=435)
  9.               - 如果连接对象connection是从连接池中获取的，那么调用connection . close（）方法则不会关闭连接而是归还连接
  10.         - 一般不由我们实现，有数据厂商来实现
  11.               - C3P0：数据库连接池技术
  12.               - Druid：数据库连接池实现技术，由阿里巴巴提供

C3P0：数据库连接技术

1. 步骤

  1.   - 导入jar包<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582207444215-4abf08b4-bd8a-4fdf-8a1c-b1fb135d5bdd.png#align=left&display=inline&height=31&name=image.png&originHeight=31&originWidth=808&size=49964&status=done&style=none&width=808)
  2.   - 不搞这个了，难搞死了

Druid：数据库连接技术

1. 步骤

  1.   - 导入jar包（只有一个）<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582230320339-65c8f04f-e8cd-4b87-9f73-f8e04c40d9af.png#align=left&display=inline&height=31&name=image.png&originHeight=31&originWidth=178&size=1397&status=done&style=none&width=178)
  2.   - 搞配置文件（这里有可能会报一个时间上的错，老方法解决，文件名是druid.properties）<br />
  1. driverClassName=com.mysql.cj.jdbc.Driver
  2. url=jdbc:mysql://127.0.0.1:3306/user?serverTimezone=UTC
  3. username=root
  4. password=root
  5.     #初始化连接数量
  6. initialSize=5
  7.     #最大连接数量
  8. maxActive=10
  9.     #最大等待时间
  10. maxWait=3000
  11. maxIdle=8
  12. minIdle=3
  1.   - 获取连接（这样可以用）<br />
  1. package druid;
  3. import com.alibaba.druid.pool.DruidDataSourceFactory;
  5. import javax.sql.DataSource;
  6. import java.io.InputStream;
  7. import java.sql.Connection;
  8. import java.util.Properties;
  10. public class DruidDemo {
  11.     public static void main(String[] args) throws Exception {
  12.         //1.导入jar包，只有druid-1.0.9.jar
  13.         //2.定义配置文件，即druid.properties
  14.         //3.加载配置文件
  15.         Properties pro = new Properties();
  16.         InputStream is = DruidDemo.class.getClassLoader().getResourceAsStream("druid.properties");
  17.         pro.load(is);
  18.         //4.获取连接池对象
  19.         DataSource ds = DruidDataSourceFactory.createDataSource(pro);
  20.         //5.获取连接
  21.         Connection conn = ds.getConnection();
  22.         System.out.println(conn);
  23.     }
  24. }
  1.   - 结果（一级棒）<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582230512831-73369a22-c34c-4600-902a-0ffc42dce5db.png#align=left&display=inline&height=254&name=image.png&originHeight=254&originWidth=740&size=24462&status=done&style=none&width=740)
  2.   - 基本步骤（注意配置文件随意放置，代码里需要路径）<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582230604522-d1332b39-e323-4dc5-9242-2609cc6cfdc7.png#align=left&display=inline&height=265&name=image.png&originHeight=265&originWidth=1008&size=245961&status=done&style=none&width=1008)

2. 配合工具类使用

  1.   - 注：关于汉字乱码的问题暂时没有好的办法解决，在sqlyog中乱码比较严重（已解决，详见杂）
  2.   - 工具类的书写（类名叫做JDBCUtils，全部写静态方法）<br />
  1. package utils;
  3. import com.alibaba.druid.pool.DruidDataSourceFactory;
  5. import javax.sql.DataSource;
  6. import java.io.IOException;
  7. import java.sql.Connection;
  8. import java.sql.ResultSet;
  9. import java.sql.SQLException;
  10. import java.sql.Statement;
  11. import java.util.Properties;
  13. /**
  14.  * Druid连接池工具类
  15.  */
  16. public class JDBCUtils {
  17.     //定义成员变量DataSource
  18.     private static DataSource ds;
  20.     static {
  22.         try {
  23.             //加载配置文件
  24.             Properties pro = new Properties();
  25.             pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
  26.             //2.获取DataSource
  27.             ds = DruidDataSourceFactory.createDataSource(pro);
  28.         } catch (IOException e) {
  29.             e.printStackTrace();
  30.         } catch (Exception e) {
  31.             e.printStackTrace();
  32.         }
  33.     }
  34.     /**
  35.      * 获取连接
  36.      */
  37.     public static Connection getConnection() throws SQLException {
  38.         return ds.getConnection();
  39.     }
  41.     /**
  42.      * 释放资源
  43.      */
  44.     public  static void close(ResultSet rs ,Statement stmt, Connection conn){
  45.         if(rs != null){
  46.             try {
  47.                 rs.close();
  48.             } catch (SQLException e) {
  49.                 e.printStackTrace();
  50.             }
  51.         }
  53.         if(stmt != null){
  54.             try {
  55.                 stmt.close();
  56.             } catch (SQLException e) {
  57.                 e.printStackTrace();
  58.             }
  59.         }
  61.         if (conn != null){
  62.             try {
  63.                 conn.close();//归还连接
  64.             } catch (SQLException e) {
  65.                 e.printStackTrace();
  66.             }
  67.         }
  68.     }
  69.     //假重载，直接穿空，可以简化代码
  70.     public  static void close(Statement stmt,Connection conn){
  71.         close(null,stmt,conn);
  72.     }
  74.     /**
  75.      * 获取连接池的方法
  76.      */
  77.     public  static DataSource getDataSource(){
  78.         return  ds;
  79.     }
  80. }
  1.   - 工具类的使用（与连接池配合使用）
  1. package druid;
  3. import utils.JDBCUtils;
  5. import java.sql.Connection;
  6. import java.sql.PreparedStatement;
  7. import java.sql.SQLException;
  9. public class DruidDemo {
  10.     public static void main(String[] args) throws Exception {
  11.         Connection conn=null;
  12.         PreparedStatement pstmt=null;
  13.         try {
  14.             //获取连接
  15.             conn = JDBCUtils.getConnection();
  16.             //定义sql
  17.             String sql = "insert into xiaoming values(?,?,?)";
  18.             //获取pstmt对象
  19.             pstmt = conn.prepareStatement(sql);
  20.             //给？赋值
  21.             pstmt.setString(1, "16");
  22.             pstmt.setString(2, "明");
  23.             pstmt.setString(3, "2020-01-28");
  24.             //执行sql
  25.             int count = pstmt.executeUpdate();
  26.             System.out.println(count);
  27.         }catch (SQLException e){
  28.             e.printStackTrace();
  29.         }finally {
  30.             //释放资源
  31.             JDBCUtils.close(pstmt,conn);
  32.         }
  34.     }
  35. }
  1.   - 注意：
  2.         - 这里使用了？来输入存储的数据

JDBCTemplate：快捷工具

1. 步骤

  1.   - 导入jar包（一共有5个，如下）<br />[commons-logging-1.2.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995572624-ef0d8c9d-c4a0-4afa-a279-6e1e92ee6716.jar?_lake_card=%7B%22uid%22%3A%221582293114360-0%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995572624-ef0d8c9d-c4a0-4afa-a279-6e1e92ee6716.jar%22%2C%22name%22%3A%22commons-logging-1.2.jar%22%2C%22size%22%3A61829%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22IMLoy%22%2C%22card%22%3A%22file%22%7D)[spring-beans-5.1.10.RELEASE.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995572725-41c92f2b-06d2-4180-ba1d-fb5676d8e308.jar?_lake_card=%7B%22uid%22%3A%221582293114360-1%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995572725-41c92f2b-06d2-4180-ba1d-fb5676d8e308.jar%22%2C%22name%22%3A%22spring-beans-5.1.10.RELEASE.jar%22%2C%22size%22%3A673979%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22ahumy%22%2C%22card%22%3A%22file%22%7D)[spring-core-5.1.10.RELEASE.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995572842-be83d186-a8e4-4191-9632-d102288c95da.jar?_lake_card=%7B%22uid%22%3A%221582293114360-2%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995572842-be83d186-a8e4-4191-9632-d102288c95da.jar%22%2C%22name%22%3A%22spring-core-5.1.10.RELEASE.jar%22%2C%22size%22%3A1301116%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%227ju53%22%2C%22card%22%3A%22file%22%7D)[spring-jdbc-5.1.10.RELEASE.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995572961-28c799f8-eda7-4c27-92c2-1daf26ae53b3.jar?_lake_card=%7B%22uid%22%3A%221582293114360-3%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995572961-28c799f8-eda7-4c27-92c2-1daf26ae53b3.jar%22%2C%22name%22%3A%22spring-jdbc-5.1.10.RELEASE.jar%22%2C%22size%22%3A404657%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22bUpvb%22%2C%22card%22%3A%22file%22%7D)[spring-tx-5.1.10.RELEASE.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995573054-15ae3192-9f49-445b-b2b6-7cb3c014143e.jar?_lake_card=%7B%22uid%22%3A%221582293114360-4%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995573054-15ae3192-9f49-445b-b2b6-7cb3c014143e.jar%22%2C%22name%22%3A%22spring-tx-5.1.10.RELEASE.jar%22%2C%22size%22%3A256437%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22t0GEa%22%2C%22card%22%3A%22file%22%7D)
  2.   - 使用演示（这里需要上文提到的自定义工具类）<br />
  1. package druid;
  3. import org.springframework.jdbc.core.JdbcTemplate;
  4. import utils.JDBCUtils;
  6. import java.sql.Connection;
  7. import java.sql.PreparedStatement;
  8. import java.sql.SQLException;
  10. public class DruidDemo {
  11.     public static void main(String[] args) {
  12.         //1.导入jar包
  13.         //2.创建JDBCTemplate对象
  14.         JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
  15.         //3.调用方法
  16.         String sql = "update xiaoming set name = 'ming' where age = 15";
  17.         int count = template.update(sql);
  18.         System.out.println(count);
  19.     }
  20. }

2. 方法介绍

  1.   - 所有方法简介<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582293358133-e96b3f32-f511-4f06-bf8d-50fba90fce2b.png#align=left&display=inline&height=162&name=image.png&originHeight=162&originWidth=791&size=248168&status=done&style=none&width=791)
  3.   - 插入<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582294292415-22649504-4fa7-4ed6-a776-fae12c56eab9.png#align=left&display=inline&height=150&name=image.png&originHeight=150&originWidth=739&size=15100&status=done&style=none&width=739)
  4.   - 删除<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582294411584-68beee44-c943-4e83-87aa-fc39fb389268.png#align=left&display=inline&height=84&name=image.png&originHeight=84&originWidth=590&size=7183&status=done&style=none&width=590)
  5.   - 封装成Map对象（只能封装单个id）<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582295919055-228f6cc0-9a94-4b53-a61f-b8c5d33147e3.png#align=left&display=inline&height=89&name=image.png&originHeight=89&originWidth=617&size=8303&status=done&style=none&width=617)<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582295933159-e844a91b-6ac6-4e37-be6e-b4fa79e5ea49.png#align=left&display=inline&height=32&name=image.png&originHeight=32&originWidth=443&size=2175&status=done&style=none&width=443)
  6.   - 将全部数据封装成list对象（成员是Map对象）<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582296502033-d306f2e4-2cb6-412b-a99d-e08def48f4d7.png#align=left&display=inline&height=131&name=image.png&originHeight=131&originWidth=608&size=10738&status=done&style=none&width=608)<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582296519903-b79200c9-4ea8-4c43-865c-2813ce4c9404.png#align=left&display=inline&height=77&name=image.png&originHeight=77&originWidth=514&size=6089&status=done&style=none&width=514)
  7.   - 将全部记录封装为Emp对象的List集合（这个方法是比较方便的一个，只是被封装了）<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582303138724-7b485395-6190-4ef4-ac40-e735e89106f4.png#align=left&display=inline&height=158&name=image.png&originHeight=158&originWidth=780&size=15428&status=done&style=none&width=780)<br />小前提（弄个Emp的类，加入getter,setter,tostring,注意类变量是数据库行名称，不能用基本类型）<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582303272515-93cd990e-254d-4aa3-8b2b-dcc695616e06.png#align=left&display=inline&height=193&name=image.png&originHeight=193&originWidth=314&size=8497&status=done&style=none&width=314)![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582303251746-b3573059-6ff0-4152-93c5-b559e22919be.png#align=left&display=inline&height=108&name=image.png&originHeight=108&originWidth=349&size=5240&status=done&style=none&width=349)
  8.   - 查询总记录数（查询的总的数量而不是数字相加，queryForObject用来处理聚合函数）<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582303721428-9fbd6f7a-ede7-4cc7-90d3-0f4badfd4045.png#align=left&display=inline&height=117&name=image.png&originHeight=117&originWidth=634&size=10657&status=done&style=none&width=634)<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582303730853-959a28fb-8502-4f26-b093-f7e6cce70a45.png#align=left&display=inline&height=31&name=image.png&originHeight=31&originWidth=47&size=243&status=done&style=none&width=47)

3. 梳理

  1.   - 需要导入的包
  2.         - 数据库连接包<br />[mysql-connector-java-8.0.19.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995573149-fbd04fa3-787d-485c-ba77-fb03a136b1a8.jar?_lake_card=%7B%22uid%22%3A%221582303835412-0%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995573149-fbd04fa3-787d-485c-ba77-fb03a136b1a8.jar%22%2C%22name%22%3A%22mysql-connector-java-8.0.19.jar%22%2C%22size%22%3A2356711%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22Dgfqm%22%2C%22card%22%3A%22file%22%7D)
  3.         - templata的包<br />[commons-logging-1.2.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995573285-8fd7bfb6-9336-481d-861c-7b2e11a1c280.jar?_lake_card=%7B%22uid%22%3A%221582303890146-0%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995573285-8fd7bfb6-9336-481d-861c-7b2e11a1c280.jar%22%2C%22name%22%3A%22commons-logging-1.2.jar%22%2C%22size%22%3A61829%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22G0N3f%22%2C%22card%22%3A%22file%22%7D)<br />[spring-beans-5.1.10.RELEASE.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995573399-5fee85d9-3ff3-4398-9a7c-1cb91ffe89a4.jar?_lake_card=%7B%22uid%22%3A%221582303890146-1%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995573399-5fee85d9-3ff3-4398-9a7c-1cb91ffe89a4.jar%22%2C%22name%22%3A%22spring-beans-5.1.10.RELEASE.jar%22%2C%22size%22%3A673979%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22bgZsL%22%2C%22card%22%3A%22file%22%7D)[spring-core-5.1.10.RELEASE.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995573560-c22ab6fc-327a-416f-b773-5dec57bebdc9.jar?_lake_card=%7B%22uid%22%3A%221582303890146-2%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995573560-c22ab6fc-327a-416f-b773-5dec57bebdc9.jar%22%2C%22name%22%3A%22spring-core-5.1.10.RELEASE.jar%22%2C%22size%22%3A1301116%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%227KoTc%22%2C%22card%22%3A%22file%22%7D)<br />[spring-jdbc-5.1.10.RELEASE.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995573665-e5ceab61-04ce-4de9-9a28-fbd810aca2a6.jar?_lake_card=%7B%22uid%22%3A%221582303890146-3%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995573665-e5ceab61-04ce-4de9-9a28-fbd810aca2a6.jar%22%2C%22name%22%3A%22spring-jdbc-5.1.10.RELEASE.jar%22%2C%22size%22%3A404657%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22QMdxH%22%2C%22card%22%3A%22file%22%7D)<br />[spring-tx-5.1.10.RELEASE.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995573776-cf32c5d1-20c8-410e-b793-a4f44fe3b1d0.jar?_lake_card=%7B%22uid%22%3A%221582303890146-4%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995573776-cf32c5d1-20c8-410e-b793-a4f44fe3b1d0.jar%22%2C%22name%22%3A%22spring-tx-5.1.10.RELEASE.jar%22%2C%22size%22%3A256437%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22P5PTp%22%2C%22card%22%3A%22file%22%7D)
  4.         - 连接池的包包<br />[druid-1.0.9.jar](https://www.yuque.com/attachments/yuque/0/2020/jar/710889/1592995573894-1a07297f-f453-4101-a9ea-af2c53fc5b74.jar?_lake_card=%7B%22uid%22%3A%221582304010178-0%22%2C%22src%22%3A%22https%3A%2F%2Fwww.yuque.com%2Fattachments%2Fyuque%2F0%2F2020%2Fjar%2F710889%2F1592995573894-1a07297f-f453-4101-a9ea-af2c53fc5b74.jar%22%2C%22name%22%3A%22druid-1.0.9.jar%22%2C%22size%22%3A1848389%2C%22type%22%3A%22%22%2C%22ext%22%3A%22jar%22%2C%22progress%22%3A%7B%22percent%22%3A99%7D%2C%22status%22%3A%22done%22%2C%22percent%22%3A0%2C%22id%22%3A%22NBPn0%22%2C%22card%22%3A%22file%22%7D)
  5.   - 需要创建的配置文件
  6.         - **druid.properties**（用来建立与Mysql的连接，这里定义数据库）<br />
  1. driverClassName=com.mysql.cj.jdbc.Driver
  2. url=jdbc:mysql://127.0.0.1:3306/user?serverTimezone=UTC
  3. username=root
  4. password=root
  5. initialSize=5
  6. maxActive=10
  7. maxWait=3000
  8. maxIdle=8
  9. minIdle=3
  1.         - **JDBCUtils**（Druid连接池的工具类）<br />
  1. package utils;
  3. import com.alibaba.druid.pool.DruidDataSourceFactory;
  5. import javax.sql.DataSource;
  6. import java.io.IOException;
  7. import java.sql.Connection;
  8. import java.sql.ResultSet;
  9. import java.sql.SQLException;
  10. import java.sql.Statement;
  11. import java.util.Properties;
  13. /**
  14.  * Druid连接池工具类
  15.  */
  16. public class JDBCUtils {
  17.     //定义成员变量DataSource
  18.     private static DataSource ds;
  20.     static {
  22.         try {
  23.             //加载配置文件
  24.             Properties pro = new Properties();
  25.             pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
  26.             //2.获取DataSource
  27.             ds = DruidDataSourceFactory.createDataSource(pro);
  28.         } catch (IOException e) {
  29.             e.printStackTrace();
  30.         } catch (Exception e) {
  31.             e.printStackTrace();
  32.         }
  33.     }
  34.     /**
  35.      * 获取连接
  36.      */
  37.     public static Connection getConnection() throws SQLException {
  38.         return ds.getConnection();
  39.     }
  41.     /**
  42.      * 释放资源
  43.      */
  44.     public  static void close(ResultSet rs ,Statement stmt, Connection conn){
  45.         if(rs != null){
  46.             try {
  47.                 rs.close();
  48.             } catch (SQLException e) {
  49.                 e.printStackTrace();
  50.             }
  51.         }
  53.         if(stmt != null){
  54.             try {
  55.                 stmt.close();
  56.             } catch (SQLException e) {
  57.                 e.printStackTrace();
  58.             }
  59.         }
  61.         if (conn != null){
  62.             try {
  63.                 conn.close();//归还连接
  64.             } catch (SQLException e) {
  65.                 e.printStackTrace();
  66.             }
  67.         }
  68.     }
  69.     //假重载，直接穿空，可以简化代码
  70.     public  static void close(Statement stmt,Connection conn){
  71.         close(null,stmt,conn);
  72.     }
  74.     /**
  75.      * 获取连接池的方法
  76.      */
  77.     public  static DataSource getDataSource(){
  78.         return  ds;
  79.     }
  80. }
  1.         - **Emp（**封装为JavaBean对象时需要用到的类，这里仅仅用于实验用的数据库，使用前要修改**）<br />**
  1. package domain;
  3. import java.util.Date;
  5. public class Emp {
  6.     private Integer age;
  7.     private String name;
  8.     private Date birthday;
  10.     public Integer getAge() {
  11.         return age;
  12.     }
  14.     public void setAge(Integer age) {
  15.         this.age = age;
  16.     }
  18.     public String getName() {
  19.         return name;
  20.     }
  22.     public void setName(String name) {
  23.         this.name = name;
  24.     }
  26.     public Date getBirthday() {
  27.         return birthday;
  28.     }
  30.     public void setBirthday(Date birthday) {
  31.         this.birthday = birthday;
  32.     }
  34.     @Override
  35.     public String toString() {
  36.         return "Emp{" +
  37.                 "age=" + age +
  38.                 ", name='" + name + '\'' +
  39.                 ", birthday=" + birthday +
  40.                 '}';
  41.     }
  42. }
  1.         - 总述<br />![image.png](https://cdn.nlark.com/yuque/0/2020/png/710889/1582308282834-57ea6360-8149-4728-b2c5-af86e2594978.png#align=left&display=inline&height=583&name=image.png&originHeight=583&originWidth=518&size=51643&status=done&style=none&width=518)