编写自己的Springboot启动类

关于springboot starter

我们在使用springboot时, 会使用到各种starter, 这些starter提高了我们开发效率, 至于starter是什么? 它是怎么启动的? 在这里我们要对其做一个详细的了解

启动器

springboot的启动器, springboot在启动时会扫描所有包下面的 META_INF/spring.factories 文件, 将该文件中所有启动类全部加载到spring容器中, 我们只需要在 application.yml 中设置对应的启动配置文件即可

实现一个mysql启动类

1. 创建maven项目, 添加下面的依赖包

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.3.4.RELEASE</version>
            <scope>import</scope>
            <type>pom</type>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-configuration-processor</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

2. 编写配置类和启动类

# 配置类
@Data
@ConfigurationProperties(prefix = "inus.mysql")
//@Component
public class MysqlProperites {
    private String driverClassName;
    private String url;
    private String username;
    private String password;
}

# 启动类
@Configuration
@ConditionalOnWebApplication
@EnableConfigurationProperties(MysqlProperites.class)
//@ComponentScan("com.inus.nacos")
public class MysqlStarterConfiguration {
    @Autowired
    private MysqlProperites properites;

    @Bean
    public Connection connection() throws ClassNotFoundException, SQLException {
        Class.forName(properites.getDriverClassName());
        Connection connection = DriverManager.getConnection(properites.getUrl(), properites.getUsername(),
                properites.getPassword());
        return connection;
    }
}

3. 启动类添加自启动

# 新建META-INF/spring.factories

# 添加启动配置类
# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.inus.nacos.configuration.MysqlStarterConfiguration

至此mysql启动类已经编写完成, 下面我们写个测试程序测试该启动类

测试mysql启动类

1. yml配置

inus:
  mysql:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/xbb_oa?useUnicode=true&characterEncoding=utf8&serverTimezone=CTT
    username: root
    password: root

2. 注入启动类中的connection

@Autowired
private Connection connection;

@RequestMapping("user")
public User user(String id) throws SQLException {
    PreparedStatement statement = connection.prepareStatement("select * from oa_user where id=?");
    statement.setString(1, id);

    User user = null;
    ResultSet rs = statement.executeQuery();
    while (rs.next()) {
        user = new User()//
                .setName(rs.getString("name"))//
                .setAccount(rs.getString("account"));
        break;
    }
    return user;
}

微信截图_20201012104051.png