SpringBoot--自动加载

1 单执行main方法后执行的事情如下：

在org.springframework.boot.autoconfigure.spring.factories中部分配置如下:

org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\

从上可知，Redis是自动配置的。

2 Redis配置修改
在RedisAutoConfiguration中：

@Configuration
@ConditionalOnClass({ JedisConnection.class, RedisOperations.class, Jedis.class })
//在项目中发现了JedisConnection.class, RedisOperations.class, Jedis.class会初始化redis配置。
@EnableConfigurationProperties(RedisProperties.class)
public class RedisAutoConfiguration {

通过查阅全局配置文档说明，可配置Redis服务器相关信息：

# REDIS (RedisProperties)
spring.redis.cluster.max-redirects= # Maximum number of redirects to follow when executing commands across the cluster.
spring.redis.cluster.nodes= # Comma-separated list of "host:port" pairs to bootstrap from.
spring.redis.database=0 # Database index used by the connection factory.
spring.redis.url= # Connection URL, will override host, port and password (user will be ignored), e.g. redis://user:password@example.com:6379
spring.redis.host=localhost # Redis server host.
spring.redis.password= # Login password of the redis server.
spring.redis.ssl=false # Enable SSL support.
spring.redis.pool.max-active=8 # Max number of connections that can be allocated by the pool at a given time. Use a negative value for no limit.
spring.redis.pool.max-idle=8 # Max number of "idle" connections in the pool. Use a negative value to indicate an unlimited number of idle connections.
spring.redis.pool.max-wait=-1 # Maximum amount of time (in milliseconds) a connection allocation should block before throwing an exception when the pool is exhausted. Use a negative value to block indefinitely.
spring.redis.pool.min-idle=0 # Target for the minimum number of idle connections to maintain in the pool. This setting only has an effect if it is positive.
spring.redis.port=6379 # Redis server port.
spring.redis.sentinel.master= # Name of Redis server.
spring.redis.sentinel.nodes= # Comma-separated list of host:port pairs.
spring.redis.timeout=0 # Connection timeout in milliseconds.

在src/main/respurces下创建的application.properties文件，

spring.redis.url= 127.0.0.1

当执行SpringApplication初始化时，会自动初始化Redis相关的信息。

@ConfigurationProperties(prefix = "spring.redis")
public class RedisProperties {

	/**
	 * Database index used by the connection factory.
	 */
	private int database = 0;

	/**
	 * Redis url, which will overrule host, port and password if set.
	 */
	private String url;

	/**
	 * Redis server host.
	 */
	private String host = "localhost";

如上，将会在application.properties中找spring.redis前缀的配置信息，例如spring.redis.url的值映射到String url中。
部分摘自某智播客。

3 创建一个自定义加载的模块，类似于启动的时候自动加载spring.factory中的内容。
application.properties:

hello.msg=hello

配置文件映射对应的类：

@ConfigurationProperties(prefix="hello")
public class HelloProperties {
	
	private final String MSG="WORLD";
	
	private String msg=MSG;

	public String getMsg() {
		return msg;
	}

	public void setMsg(String msg) {
		this.msg = msg;
	}
}

被自动创建的服务:

public class HelloService {	
	
	private String msg;

	public String sayHello(){
		return "hello"+this.msg;
	}

	public String getMsg() {
		return msg;
	}

	public void setMsg(String msg) {
		this.msg = msg;
	}
}

自动创建中心：

@Configuration
@EnableConfigurationProperties(HelloProperties.class)//开启声明注入，将配置文件中的值映射到变量中
@ConditionalOnClass(HelloService.class)//判断HelloService在类路径中是否存在，
@ConditionalOnProperty(prefix="hello",value="enabled",matchIfMissing=true)
public class HelloServiceAutoConfiguration {

	@Autowired
	private HelloProperties helloProperties;
	
	@Bean
	@ConditionalOnMissingBean(HelloService.class)//没有的情况下自动创建
	public HelloService helloService(){
		HelloService helloService=new HelloService();
		helloService.setMsg(helloProperties.getMsg());
		return helloService;
	}
}

在src/main/resources/下创建META-INF文件夹后在META-INF装中创建spring.factories，

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.text.springboot.autoconfigure.hello.HelloServiceAutoConfiguration

Maven clean一下项目后install，在另外一个项目中依赖。启动

<dependencies>
		<dependency>
			<groupId>text</groupId>
			<artifactId>helloworld</artifactId>
			<version>0.0.1-SNAPSHOT</version>
		</dependency>
		
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-autoconfigure</artifactId>
			<version>1.5.2.RELEASE</version>
		</dependency>
		
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
			<version>1.5.2.RELEASE</version>
		</dependency>
	</dependencies>

打开debug模式：
application.properties

debug=true

启动：

@RestController
@SpringBootApplication
public class TextApplication {

	@Autowired
	private HelloService helloService;
	
	@RequestMapping("/")
	public String index(){
		return helloService.sayHello();
	}
	
	public static void main(String[] args) {
		SpringApplication.run(TextApplication.class, args);
	}
}

执行结果：
在
Positive matches:

中查看到HelloService已自动加载。
访问根目录：

注入配置到map变量中

    @Value("#{${message.onlineBigAreaOperatorManager}}")
    private Map<String,Integer> onlineBigAreaOperatorManager;

#message:
#  onlineBigAreaOperatorManager: 111111111111111111

# 不行
#message:
#  onlineBigAreaOperatorManager: {a: 1}

# 可以
message:
  onlineBigAreaOperatorManager: "{'11060108': 615181649}"

# 不行
#message:
#  onlineBigAreaOperatorManager[aaaa]: 1111

# 不行
#message:
#  onlineBigAreaOperatorManager:
#    aaaaa: 1111

参考：@Value和@ConfigurationProperties 注入值问题可以参考 https://juejin.cn/post/7315727549376430116