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五、配置数据源 ​

一、数据源（连接池）的作用 ​

  • 数据源(连接池)是提高程序性能如出现的
  • 事先实例化数据源，初始化部分连接资源
  • 使用连接资源时从数据源中获取
  • 使用完毕后将连接资源归还给数据源

二、 数据源的开发步骤 ​

  1. 导入数据源的坐标和数据库驱动坐标
  2. 创建数据源对象
  3. 设置数据源的基本连接数据
  4. 使用数据源获取连接资源和归还连接资源

1、手动创建c3p0数据源 ​


（1）相关依赖 ​

xml
<dependencies>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.33</version>
    </dependency>
    
    <dependency>
        <groupId>c3p0</groupId>
        <artifactId>c3p0</artifactId>
        <version>0.9.1.2</version>
    </dependency>
    
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
</dependencies>

（2）测试 ​

java
@Test
//测试手动创建c3p0数据源
public void connectDatabase() throws Exception {
    ComboPooledDataSource dataSource=new ComboPooledDataSource();
    dataSource.setDriverClass("com.mysql.cj.jdbc.Driver");
    dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/test");
    dataSource.setUser("root");
    dataSource.setPassword("123456");
    
    Connection connection = dataSource.getConnection();
    System.out.println(connection);
    
    connection.close();
}

2、手动创建druid数据源 ​


（1）相关依赖 ​

xml
<dependencies>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.33</version>
    </dependency>
    
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.2.20</version>
    </dependency>
    
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
</dependencies>

（2）测试 ​

java
@Test
//测试手动创建druid数据源
public void connectDatabase() throws Exception {
    DruidDataSource dataSource = new DruidDataSource();
    dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
    dataSource.setUrl("jdbc:mysql://localhost:3306/test");
    dataSource.setUsername("root");
    dataSource.setPassword("123456");
    
    DruidPooledConnection connection = dataSource.getConnection();
    System.out.println(connection);
    
    connection.close();
}

3、配置文件解决硬编码问题 ​


（1）jdbc.properties ​

properties
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=123456

（2）测试 ​

java
@Test
public void connectDatabase() throws Exception {
    //解析配置文件，getBundle专门对properties进行读取
    ResourceBundle rb=ResourceBundle.getBundle("jdbc");
    String driver = rb.getString("jdbc.driver");
    String url = rb.getString("jdbc.url");
    String username = rb.getString("jdbc.username");
    String password = rb.getString("jdbc.password");
    
    ComboPooledDataSource dataSource=new ComboPooledDataSource();
    dataSource.setDriverClass(driver);
    dataSource.setJdbcUrl(url);
    dataSource.setUser(username);
    dataSource.setPassword(password);
    
    Connection connection = dataSource.getConnection();
    System.out.println(connection);
    connection.close();
}

4、Spring容器创建c3p0数据源 ​


（1）applicationContext.xml ​

xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation=
               "http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
                http://www.springframework.org/schema/context  http://www.springframework.org/schema/context/spring-context.xsd
">
	<!-- 读取properties配置文件 -->
    <context:property-placeholder location="classpath:jdbc.properties"/>

    <bean id="comboPooledDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="${jdbc.driver}"></property>
        <property name="jdbcUrl" value="${jdbc.url}"></property>
        <property name="user" value="${jdbc.username}"></property>
        <property name="password" value="${jdbc.password}"></property>
    </bean>
    
</beans>

（2）测试 ​

java
 @Test
 //Spring创建c3p0数据源
 public void connectDatabase() throws Exception {
     ApplicationContext app=new ClassPathXmlApplicationContext("applicationContext.xml");
     ComboPooledDataSource dataSource = app.getBean(ComboPooledDataSource.class);
     Connection connection = dataSource.getConnection();
     System.out.println(connection);
     connection.close();
 }

5、Spring容器创建druid数据源 ​


（1）applicationContext.xml ​

xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation=
               "http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
                http://www.springframework.org/schema/context  http://www.springframework.org/schema/context/spring-context.xsd
">
	<!-- 读取properties配置文件 -->
    <context:property-placeholder location="classpath:jdbc.properties"/>

    <bean id="druidDataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="${jdbc.driver}"></property>
        <property name="url" value="${jdbc.url}"></property>
        <property name="username" value="${jdbc.username}"></property>
        <property name="password" value="${jdbc.password}"></property>
    </bean>
    
</beans>

（2）测试 ​

java
@Test
//Spring创建druid数据源
public void connectDatabase() throws Exception {
    ApplicationContext app=new ClassPathXmlApplicationContext("applicationContext.xml");
    
    DruidDataSource dataSource = app.getBean(DruidDataSource.class);
    Connection connection = dataSource.getConnection();
    
    System.out.println(connection);
    connection.close();
}