SpringBoot - starter mysql dome

SpringBoot starter

1. 使用maven创建两个项目

enable-common 为了测试 mysql-starter

2. mysql-starter 项目添加pom.xml内容

 	<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.48</version></dependency>

3.mysql-starter 配置mysql连接的属性

// 读取配置文件中前缀为 mysql的内容
@ConfigurationProperties(prefix = "mysql")
public class MysqlProperties {
    // 以下所有属性全部为默认值private String url = "jdbc:mysql://localhost:3306/test";private String user = "root";private String password = "root";private String driverName = "com.mysql.jdbc.Driver";public String getUrl() {
    return url;}public void setUrl(String url) {
    this.url = url;}public String getUser() {
    return user;}public void setUser(String user) {
    this.user = user;}public String getPassword() {
    return password;}public void setPassword(String password) {
    this.password = password;}public String getDriverName() {
    return driverName;}public void setDriverName(String driverName) {
    this.driverName = driverName;}
}

4. mysql-starter 创建生成mysql连接 Connection 的配置类

// 这个配置类也需要被注入到spring上下文中
@Configuration
// 因为MysqlProperties类没有自动注入, 所以需要在配置类中使用,就必须使用该注解注入
@EnableConfigurationProperties(MysqlProperties.class)
public class MysqlConfigure {
    @Bean(name = "mysqlConnection")// lombok 提供的异常捕获注解@lombok.SneakyThrowspublic java.sql.Connection getConnection(MysqlProperties properties){
    // 加载驱动Class.forName(properties.getDriverName());// 建立链接return DriverManager.getConnection(properties.getUrl(),properties.getUser(), properties.getPassword());}
}

5. mysql-starter 在resources目录下创建 META-INF/spring.factories文件

###  注意, 这里前缀是固定的,后缀必须配置自己写的配置类,而不是属性类
org.springframework.boot.autoconfigure.EnableAutoConfiguration=org.example.config.MysqlConfigure

6. 配置enable-common项目pom.xml 文件

<!-- 这里引入自己写的starter -->
<!-- 这个项目中不需要再次引入spring-boot-starter , mysql-starter已经包含了-->
<dependency><groupId>org.example</groupId><artifactId>mysql-starter</artifactId><version>1.0-SNAPSHOT</version>
</dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId>
</dependency>

7. enable-common配置启动类

@SpringBootApplication
public class CommonAutoConfigureApplication {
    public static void main(String[] args) {
    SpringApplication.run(CommonAutoConfigureApplication.class, args);}
}

8. enable-common 使用Junit 测试

@RunWith(SpringRunner.class)
@SpringBootTest(classes = CommonAutoConfigureApplication.class)
public class MySQLTest {
    @Resource(name = "mysqlConnection")private Connection connection;@Test@SneakyThrowspublic void testMyStarter(){
    Statement statement = connection.createStatement();ResultSet rs = statement.executeQuery("select * from tb_user");while (rs.next()) {
    // 通过字段检索String id = rs.getString("id");String name = rs.getString("mobile");String password = rs.getString("email");System.out.print(" id:" + id);System.out.print(" 电话:" + name);System.out.print(" 邮箱:" + password + "\n");}rs.close();statement.close();connection.close();//id:1 电话:123456 邮箱:xxx@163.com//id:2 电话:456789 邮箱:xxx@163.com}
}

9. spring.factories中前缀去哪儿找

• 进入注解 @SpringBootApplication内部找到 @EnableAutoConfiguration

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration  // ****找到该注解***
@ComponentScan(excludeFilters = {
     @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {
    

• @EnableAutoConfiguration复制该注解的全路径即可

10. resource/META-INF/spring.factories 源码中能找到吗

• 重复第九步, 进入@EnableAutoConfiguration注解中找到@Import(AutoConfigurationImportSelector.class)

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)  // ***这里***
public @interface EnableAutoConfiguration {
    

• 进入AutoConfigurationImportSelector.class类中 177 行

// 找到该方法 
//org.springframework.boot.autoconfigure.AutoConfigurationImportSelector#getCandidateConfigurations()
protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
    List<String> configurations = SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(),getBeanClassLoader());Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you "+ "are using a custom packaging, make sure that file is correct.");return configurations;}

11. 总结

(1). 写starter需要依赖spring项目的自动注入和IOC容器.
(2). 在写spring.factories时候一定要放到starter项目中resource/META-INF目录下
(3). 如果需要修改 mysql 的连接属性, 直接在enable-common 中 application.yml添加 以mysql为前缀的内容即可

mysql:driverName: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/cloud_user?useSSL=falseuser: rootpassword: root

(4). 代码地址: https://github.com/Zyred9/boot-starters