Spring Boot核心特性与整合：配置加载优先级终极解密

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

命令行参数 → 系统属性 → 环境变量 → 配置文件 → @PropertySource注解 → 默认属性

@Bean
public TomcatServletWebServerFactory tomcatFactory() {
    return new TomcatServletWebServerFactory() {
        @Override
        protected void postProcessContext(Context context) {
            // 自定义容器配置
        }
    };
}

management.endpoints.web.exposure.include=health,info,metrics
management.metrics.export.prometheus.enabled=true

java -jar app.jar --server.port=8081 --spring.datasource.url=jdbc:mysql://new-host:3306/db

java -Dspring.profiles.active=prod -Dlogging.level.root=WARN -jar app.jar

export SPRING_PROFILES_ACTIVE=cloud

@Configuration
@PropertySource("classpath:custom.properties")
public class CustomConfig { ... }

new SpringApplicationBuilder(MyApp.class)
    .properties("spring.main.banner-mode=off")
    .run(args);

public interface PropertySourceLoader {
    // 返回支持的文件扩展名（不包含"."）
    String[] getFileExtensions();
    
    // 将资源加载为一个或多个PropertySource
    List<PropertySource<?>> load(String name, Resource resource) throws IOException;
}

public class PropertiesPropertySourceLoader implements PropertySourceLoader {
    private static final String XML_FILE_EXTENSION = ".xml";
    
    @Override
    public String[] getFileExtensions() {
        return new String[] { "properties", "xml" };
    }
    
    @Override
    public List<PropertySource<?>> load(String name, Resource resource) throws IOException {
        Map<String, ?> properties = loadProperties(resource);
        if (properties.isEmpty()) {
            return Collections.emptyList();
        }
        return Collections.singletonList(
            new OriginTrackedMapPropertySource(name, properties));
    }
    
    private Map<String, ?> loadProperties(Resource resource) throws IOException {
        String filename = resource.getFilename();
        if (filename != null && filename.endsWith(XML_FILE_EXTENSION)) {
            return (Map) PropertiesLoaderUtils.loadProperties(resource);
        }
        return new OriginTrackedPropertiesLoader(resource).load();
    }
}

public class YamlPropertySourceLoader implements PropertySourceLoader {
    @Override
    public String[] getFileExtensions() {
        return new String[] { "yml", "yaml" };
    }
    
    @Override
    public List<PropertySource<?>> load(String name, Resource resource) throws IOException {
        if (!ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", null)) {
            throw new IllegalStateException("Attempted to load YAML configuration but SnakeYAML was not found");
        }
        List<Map<String, Object>> loaded = new OriginTrackedYamlLoader(resource).load();
        if (loaded.isEmpty()) {
            return Collections.emptyList();
        }
        List<PropertySource<?>> propertySources = new ArrayList<>(loaded.size());
        for (int i = 0; i < loaded.size(); i++) {
            String documentNumber = (loaded.size() != 1) ? " (document #" + i + ")" : "";
            propertySources.add(new OriginTrackedMapPropertySource(
                name + documentNumber, loaded.get(i)));
        }
        return propertySources;
    }
}

curl http://localhost:8080/actuator/env

@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext ctx = SpringApplication.run(DemoApplication.class, args);
        System.out.println("最终生效的端口：" + ctx.getEnvironment().getProperty("server.port"));
    }
}

public class DbPropertySource extends MapPropertySource {
    private final JdbcTemplate jdbcTemplate;
    
    public DbPropertySource(String name, DataSource dataSource) {
        super(name, new HashMap<>());
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }
    
    @Override
    public Object getProperty(String key) {
        return jdbcTemplate.queryForObject(
            "SELECT value FROM config_table WHERE key = ?", 
            String.class, key);
    }
}

public class RedisPropertySource extends PropertySource<RedisConnection> {
    public RedisPropertySource(String name) {
        super(name, RedisConfig.getConnection());
    }
    
    @Override
    public Object getProperty(String key) {
        return getSource().stringCommands().get(key);
    }
}

@Configuration
public class CustomConfigConfiguration {
    @Bean
    public PropertySourceLocator customPropertySourceLocator() {
        return new CustomPropertySourceLocator();
    }
}

public class DynamicPropertySource extends MapPropertySource {
    private long version = 0;
    
    @Override
    public Object getProperty(String key) {
        if(checkRemoteUpdate()) version++;
        return super.getProperty(key);
    }
}

# 最后激活的profile优先级最高
spring.profiles.active=dev,cloud

spring.profiles.group.production=cloud,audit

public class DecryptPropertySource extends PropertySource<String> {
    @Override
    public Object getProperty(String key) {
        String value = getSource().getProperty(key);
        return value.startsWith("ENC(") ? decrypt(value) : value;
    }
}

java -jar app.jar --server.port=8081 --spring.datasource.url=jdbc:mysql://localhost:3306/test?useSSL=false

export DB_PASSWORD=secret && java -jar app.jar

$env:DB_PASSWORD="secret"; java -jar app.jar

java -Dspring.profiles.active=prod -jar app.jar

ENV SPRING_DATASOURCE_PASSWORD=${DB_PASSWORD}

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  SPRING_REDIS_HOST: "redis-cluster"

├── config/
│   ├── application.yml       # 基础配置
│   ├── application-dev.yml   # 开发环境
│   └── application-prod.yml  # 生产环境
└── app.jar

spring:
  config:
    import: 
      - classpath:common.yml
      - optional:file:./external.yml

SPRING_PROFILES_ACTIVE=prod,metrics java -jar app.jar

spring:
  cloud:
    vault:
      uri: https://vault.example.com
      token: ${VAULT_TOKEN}

@Configuration
@EnableNacosConfig(globalProperties = @NacosProperties(serverAddr = "${nacos.server}"))
public class NacosConfig {
}

@RefreshScope
@RestController
public class ConfigController {
    @Value("${dynamic.config}")
    private String config;
}

spring.cloud.nacos.config.override-none=true  # 本地配置优先
spring.cloud.nacos.config.override-system-properties=false

public class JsonPropertySourceLoader implements PropertySourceLoader {
    @Override
    public String[] getFileExtensions() {
        return new String[]{"json"};
    }
    
    @Override
    public List<PropertySource<?>> load(String name, Resource resource) 
        throws IOException {
        // 解析JSON文件的实现
    }
}

org.springframework.boot.env.PropertySourceLoader=\
com.example.JsonPropertySourceLoader

public class DatabasePropertySource extends EnumerablePropertySource<Object> {
    private final JdbcTemplate jdbcTemplate;
    
    public DatabasePropertySource(String name, DataSource dataSource) {
        super(name);
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }
    
    @Override
    public String[] getPropertyNames() {
        return jdbcTemplate.queryForList(
            "SELECT key FROM configs", String.class).toArray(new String[0]);
    }
    
    @Override
    public Object getProperty(String name) {
        return jdbcTemplate.queryForObject(
            "SELECT value FROM configs WHERE key = ?", 
            String.class, name);
    }
}

management.endpoint.configprops.enabled=true
management.endpoint.env.enabled=true

GET /actuator/configprops
GET /actuator/env

@SpringBootApplication
public class App {
    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(App.class);
        app.setBannerMode(Banner.Mode.OFF);
        ConfigurableApplicationContext ctx = app.run(args);
        System.out.println(ctx.getEnvironment().getPropertySources());
    }
}

spring:
  datasource:
    password: '{cipher}FKSAJDFGYOS8F7GLHAKERGFHLSAJ'

# 而不是使用root权限
sudo -u appuser java -jar app.jar

logging.level.org.springframework.core.env=DEBUG