springboot中的starter及自定义方法详解

$ pwd
/d/test/sharding-sphere/shardingsphere-jdbc/shardingsphere-jdbc-spring/shardingsphere-jdbc-core-spring/shardingsphere-jdbc-core-spring-boot-starter

provides: shardingsphere-jdbc-spring-boot-starter

{
  "groups": [
    {
      "name": "spring.shardingsphere.datasource",
      "type": "org.apache.shardingsphere.spring.boot.SpringBootConfiguration"
    },
    ...
}

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.apache.shardingsphere.spring.boot.SpringBootConfiguration

@Configuration // 代表是一个Java config类
@ComponentScan("org.apache.shardingsphere.spring.boot.converter") // 配置扫描路径，会扫描并注册相关spring bean
@EnableConfigurationProperties(SpringBootPropertiesConfiguration.class) // 启用属性类，封装了外部配置文件信息
@ConditionalOnProperty(prefix = "spring.shardingsphere", name = "enabled", havingValue = "true", matchIfMissing = true) // 当spring.shardingsphere.enabled 配置项等于true时，加载该自动配置类
@AutoConfigureBefore(DataSourceAutoConfiguration.class) // 在DataSourceAutoConfiguration自动配置类之前配置
@RequiredArgsConstructor // lombok注解
public class SpringBootConfiguration implements EnvironmentAware {
    // 属性类，会自动注入进来
    private final SpringBootPropertiesConfiguration props;
    
    private final Map<String, DataSource> dataSourceMap = new LinkedHashMap<>();
    
    // 核心，创建shardingsphere
    @Bean
    @Autowired(required = false)
    public DataSource shardingSphereDataSource(final ObjectProvider<List<RuleConfiguration>> rules) throws SQLException {
        Collection<RuleConfiguration> ruleConfigurations = Optional.ofNullable(rules.getIfAvailable()).orElse(Collections.emptyList());
        return ShardingSphereDataSourceFactory.createDataSource(dataSourceMap, ruleConfigurations, props.getProps());
    }
    
    // 创建spring bean ShardingTransactionTypeScanner
    @Bean
    public ShardingTransactionTypeScanner shardingTransactionTypeScanner() {
        return new ShardingTransactionTypeScanner();
    }
    
    // 感知上下文对象，因为自动配置类本身也是一个spring bean，所以这里可以这样子用
    @Override
    public final void setEnvironment(final Environment environment) {
        dataSourceMap.putAll(DataSourceMapSetter.getDataSourceMap(environment));
    }
}

@ConfigurationProperties(prefix = "info")
@Getter
@Setter
public class HelloProperties {
//    private Properties prop = new Properties();

    private String name;
}

@AllArgsConstructor
public class Spokesman {
    private String name;

    public String speak() {
        System.out.println("你好，向大家介绍：" + name);
        return name;
    }
}

@Configuration
@EnableConfigurationProperties(HelloProperties.class)
@ConditionalOnExpression // 默认为true，即默认加载
@AllArgsConstructor
public class HelloAutoConfiguration implements InitializingBean {
    private final HelloProperties props;

    // 创建 Spokesman 的 spring bean
    @Bean
    public Spokesman createSpokesman() {
        return new Spokesman(props.getName());
    }

    // 仅仅为了打印props，没有其他特殊用途
    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("props isss: " + props.getName());
    }
}

<dependency>
    <groupId>dongshi.daddy</groupId>
    <artifactId>hello-starter</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

info:
  name: 甜甜的葡萄干

@Resource
private Spokesman spokesman;

@RequestMapping("/starter")
@ResponseBody
public String starter() {
    System.out.println("starter ...");
    return spokesman.speak();
}