Spring配置连接数据库与SpringBoot配置连接数据库（四种属性注入方式）

设置jdbc.properties
jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/SSM
jdbc.username=root
jdbc.password=root

/**
 * @Author: Promsing
 * @Date: 2021/5/30 - 14:52
 * @Description:连接数据库的配置类
 * @version： 1.0
 */
@Configuration//声明该类是一个java配置类，相当于一个xml配置文件
@PropertySource("classpath:jdbc.properties") //读取资源文件
public class JdbcConfiguration {
    @Value("${jdbc.driverClassName}")
    private String driverClassName;
    @Value("${jdbc.url}")
    private String url;
    @Value("${jdbc.username}")
    private String username;
    @Value("${jdbc.password}")
    private String password;
    @Bean //将返回值注入到IOC容器中
    public DataSource dataSource(){
        DruidDataSource dataSource=new DruidDataSource();
        //设置连接数据库的四大参数
        dataSource.setDriverClassName(this.driverClassName);
        dataSource.setUrl(this.url);
        dataSource.setUsername(this.username);
        dataSource.setPassword(this.password);
        return dataSource;
    }
}

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/SSM
jdbc.username=root
jdbc.password=root

/**
 * @Author: Promsing
 * @Date: 2021/5/30 - 15:41
 * @Description: 封装了读取出来的配置文件
 * @version： 1.0
 */
@ConfigurationProperties(prefix = "jdbc")
public class JdbcProperties {
    private String driverClassName;
    private String url;
    private String username;
    private String password;
   public void setDriverClassName(String driverClassName) {
        this.driverClassName = driverClassName;
    }
    public void setUrl(String url) {
        this.url = url;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getDriverClassName() {
        return driverClassName;
    }
    public String getUrl() {
        return url;
    }
    public String getUsername() {
        return username;
    }
    public String getPassword() {
        return password;
    }
}

/**
 * @Author: Promsing
 * @Date: 2021/5/30 - 14:52
 * @Description: 连接数据库的Java配置类
 * @version： 1.0
 */
@Configuration//声明该类是一个java配置类，相当于一个西xml配置文件
@EnableConfigurationProperties(JdbcProperties.class) //加载JDBC的配置类
public class JdbcConfiguration {
    @Autowired
    private JdbcProperties jdbcProperties;
    //方式一
    @Bean //将返回值注入到IOC容器中
    public DataSource dataSource(){
        DruidDataSource dataSource=new DruidDataSource();
        //设置连接数据库的四大参数
        dataSource.setDriverClassName(this.jdbcProperties.getDriverClassName());
        dataSource.setUrl(this.jdbcProperties.getUrl());
        dataSource.setUsername(this.jdbcProperties.getUsername());
        dataSource.setPassword(this.jdbcProperties.getPassword());
        return dataSource;
    }
      /*
        //方式二：最优雅最简单--直接换掉方式一
        @Bean //将返回值注入到IOC容器中
        @ConfigurationProperties(prefix = "jdbc")
        public DataSource dataSource(){
            DruidDataSource dataSource=new DruidDataSource();
        return dataSource;
        }
    * */
    /*
        //方式三通过构造函数注入--在方式一上的方式修改
        public JdbcConfiguration(JdbcProperties jdbcProperties) {
            this.jdbcProperties = jdbcProperties;
        }
    * */
    /*
        //方式四通过方法的参数注入--直接换掉方式一
        public DataSource dataSource(dbcProperties jdbcProperties){
             DruidDataSource dataSource=new DruidDataSource();
            //设置连接数据库的四大参数
            dataSource.setDriverClassName(jdbcProperties.getDriverClassName());
            dataSource.setUrl(jdbcProperties.getUrl());
            dataSource.setUsername(jdbcProperties.getUsername());
            dataSource.setPassword(jdbcProperties.getPassword());
            return dataSource;
//    }
    * */
}