關于springboot starter

我們在使用springboot時, 會使用到各種starter, 這些starter提高了我們開發(fā)效率, 至于starter是什么? 它是怎么啟動的? 在這里我們要對其做一個詳細的了解

啟動器

springboot的啟動器, springboot在啟動時會掃描所有包下面的 META_INF/spring.factories 文件, 將該文件中所有啟動類全部加載到spring容器中, 我們只需要在 application.yml 中設置對應的啟動配置文件即可

實現(xiàn)一個mysql啟動類

1. 創(chuàng)建maven項目, 添加下面的依賴包

<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. 編寫配置類和啟動類

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

# 啟動類
@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. 啟動類添加自啟動

# 新建META-INF/spring.factories

# 添加啟動配置類
# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.inus.nacos.configuration.MysqlStarterConfiguration

至此mysql啟動類已經(jīng)編寫完成, 下面我們寫個測試程序測試該啟動類

測試mysql啟動類

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. 注入啟動類中的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;
}

微信截圖_20201012104051.png