SpringBoot--自動載入

1 單執行main方法後執行的事情如下：

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

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

從上可知，Redis是自動配置的。

2 Redis配置修改
在RedisAutoConfiguration中：

@Configuration
@ConditionalOnClass({ JedisConnection.class, RedisOperations.class, Jedis.class })
//在專案中發現了JedisConnection.class, RedisOperations.class, Jedis.class會初始化redis配置。
@EnableConfigurationProperties(RedisProperties.class)
public class RedisAutoConfiguration {

通過查閱全域性配置文件說明，可配置Redis伺服器相關資訊：

# 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下建立的application.properties檔案，

spring.redis.url= 127.0.0.1

當執行SpringApplication初始化時，會自動初始化Redis相關的資訊。

@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，將會在application.properties中找spring.redis字首的配置資訊，例如spring.redis.url的值對映到String url中。
部分摘自某智播客。

3 建立一個自定義載入的模組，類似於啟動的時候自動載入spring.factory中的內容。
application.properties:

hello.msg=hello

配置檔案對映對應的類：

@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;
    }
}

被自動建立的服務:

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;
    }
}

自動建立中心：

@Configuration
@EnableConfigurationProperties(HelloProperties.class)//開啟宣告注入，將配置檔案中的值對映到變數中
@ConditionalOnClass(HelloService.class)//判斷HelloService在類路徑中是否存在，
@ConditionalOnProperty(prefix="hello",value="enabled",matchIfMissing=true)
public class HelloServiceAutoConfiguration {

    @Autowired
    private HelloProperties helloProperties;

    @Bean
    @ConditionalOnMissingBean(HelloService.class)//沒有的情況下自動建立
    public HelloService helloService(){
        HelloService helloService=new HelloService();
        helloService.setMsg(helloProperties.getMsg());
        return helloService;
    }
}

在src/main/resources/下建立META-INF資料夾後在META-INF裝中建立spring.factories，

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

Maven clean一下專案後install，在另外一個專案中依賴。啟動

<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>

開啟debug模式：
application.properties

debug=true

啟動：

@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);
    }
}

執行結果：
在

Positive matches:

中檢視到HelloService已自動載入。
訪問根目錄：