一、@ConfigurationProperties註解的使用

看配置檔案，我的是yaml格式的配置：

// file application.yml
my:
  servers:
    - dev.bar.com
    - foo.bar.com
    - jiaobuchong.com

下面我要將上面的配置屬性注入到一個Java Bean類中，看碼：

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

import
 
 java.util.ArrayList;
import java.util.List;

/**
 * file: MyConfig.java
 * Created by jiaobuchong on 12/29/15.
 */
@Component      //不加這個註解的話, 使用@Autowired 就不能注入進去了
@ConfigurationProperties(prefix = "my")  // 配置檔案中的字首
public class MyConfig {
    private List<String> servers = new ArrayList<String>();
    public
 
 List<String> getServers() { return this.servers;
    }
}

下面寫一個Controller來測試一下：

/**
 * file： HelloController
 * Created by jiaobuchong on 2015/12/4.
 */
@RequestMapping("/test")
@RestController
public class HelloController {
    @Autowired
    private MyConfig myConfig;

    @RequestMapping("/config"
 
)
    public Object getConfig() {
        return myConfig.getServers();
    }
}

下面執行Application.java的main方法跑一下看看：

@Configuration   //標註一個類是配置類，spring boot在掃到這個註解時自動載入這個類相關的功能，比如前面的文章中介紹的配置AOP和攔截器時加在類上的Configuration
@EnableAutoConfiguration  //啟用自動配置 該框架就能夠進行行為的配置，以引導應用程式的啟動與執行, 根據匯入的starter-pom 自動載入配置
@ComponentScan  //掃描元件 @ComponentScan(value = "com.spriboot.controller") 配置掃描元件的路徑
public class Application {
    public static void main(String[] args) {
        // 啟動Spring Boot專案的唯一入口
        SpringApplication app = new SpringApplication(Application.class);
        app.setBannerMode(Banner.Mode.OFF);
        app.run(args);
    }

在瀏覽器的位址列裡輸入：
localhost:8080/test/config 得到：
[“dev.bar.com”,”foo.bar.com”,”jiaobuchong.com”]

二、@ConfigurationProperties和@EnableConfigurationProperties註解結合使用

在spring boot中使用yaml進行配置的一般步驟是，
1、yaml配置檔案，這裡假設：

my:
  webserver:
    #HTTP 監聽埠
    port: 80
    #嵌入Web伺服器的執行緒池配置
    threadPool:
      maxThreads: 100
      minThreads: 8
      idleTimeout: 60000

2、

//file MyWebServerConfigurationProperties.java
import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "my.webserver")
public class MyWebServerConfigurationProperties {
    private int port;
    private ThreadPool threadPool;

    public int getPort() {
        return port;
    }

    public void setPort(int port) {
        this.port = port;
    }

    public ThreadPool getThreadPool() {
        return threadPool;
    }

    public void setThreadPool(ThreadPool threadPool) {
        this.threadPool = threadPool;
    }

    public static class ThreadPool {
        private int maxThreads;
        private int minThreads;
        private int idleTimeout;

        public int getIdleTimeout() {
            return idleTimeout;
        }

        public void setIdleTimeout(int idleTimeout) {
            this.idleTimeout = idleTimeout;
        }

        public int getMaxThreads() {
            return maxThreads;
        }

        public void setMaxThreads(int maxThreads) {
            this.maxThreads = maxThreads;
        }

        public int getMinThreads() {
            return minThreads;
        }

        public void setMinThreads(int minThreads) {
            this.minThreads = minThreads;
        }
    }
}

3、

// file: MyWebServerConfiguration.java
import org.springframework.context.annotation.Configuration;
import org.springframework.boot.context.properties.EnableConfigurationProperties;

@Configuration
@EnableConfigurationProperties(MyWebServerConfigurationProperties.class)
public class MyWebServerConfiguration {
    @Autowired
    private MyWebServerConfigurationProperties properties;
    /**
     *下面就可以引用MyWebServerConfigurationProperties類       裡的配置了
    */
   public void setMyconfig() {
       String port = properties.getPort();
       // ...........
   }   
}

The @EnableConfigurationProperties annotation is automatically applied to your project so that any beans annotated with @ConfigurationProperties will be configured from the Environment properties. This style of configuration works particularly well with the SpringApplication external YAML configuration.(引自spring boot官方手冊)

三、@Bean配置第三方元件(Third-party configuration)

建立一個bean類：

// file ThreadPoolBean.java
/**
 * Created by jiaobuchong on 1/4/16.
 */
public class ThreadPoolBean {
    private int maxThreads;
    private int minThreads;
    private int idleTimeout;

    public int getMaxThreads() {
        return maxThreads;
    }

    public void setMaxThreads(int maxThreads) {
        this.maxThreads = maxThreads;
    }

    public int getMinThreads() {
        return minThreads;
    }

    public void setMinThreads(int minThreads) {
        this.minThreads = minThreads;
    }

    public int getIdleTimeout() {
        return idleTimeout;
    }

    public void setIdleTimeout(int idleTimeout) {
        this.idleTimeout = idleTimeout;
    }
}

引用前面第二部分寫的配置類：MyWebServerConfiguration.java和MyWebServerConfigurationProperties.java以及yaml配置檔案,現在修改MyWebServerConfiguration.java類：

import com.jiaobuchong.springboot.domain.ThreadPoolBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * Created by jiaobuchong on 1/4/16.
 */
@Configuration  //這是一個配置類，與@Service、@Component的效果類似。spring會掃描到這個類，@Bean才會生效，將ThreadPoolBean這個返回值類註冊到spring上下文環境中
@EnableConfigurationProperties(MyWebServerConfigurationProperties.class) //通過這個註解, 將MyWebServerConfigurationProperties這個類的配置到上下文環境中,本類中使用的@Autowired註解注入才能生效
public class MyWebServerConfiguration {
    @SuppressWarnings("SpringJavaAutowiringInspection") //加這個註解讓IDE 不報: Could not autowire
    @Autowired
    private MyWebServerConfigurationProperties properties;

    @Bean //@Bean註解在方法上,返回值是一個類的例項,並宣告這個返回值(返回一個物件)是spring上下文環境中的一個bean
    public ThreadPoolBean getThreadBean() {
        MyWebServerConfigurationProperties.ThreadPool threadPool = properties.getThreadPool();
        ThreadPoolBean threadPoolBean = new ThreadPoolBean();
        threadPoolBean.setIdleTimeout(threadPool.getIdleTimeout());
        threadPoolBean.setMaxThreads(threadPool.getMaxThreads());
        threadPoolBean.setMinThreads(threadPool.getMinThreads());
        return threadPoolBean;
    }
}

被@Configuration註解標識的類，通常作為一個配置類，這就類似於一個xml檔案，表示在該類中將配置Bean元資料，其作用類似於Spring裡面application-context.xml的配置檔案，而@Bean標籤，則類似於該xml檔案中，宣告的一個bean例項。
寫一個controller測試一下：

import com.jiaobuchong.springboot.domain.ThreadPoolBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by jiaobuchong on 2015/12/4.
 */
@RequestMapping("/first")
@RestController
public class HelloController {
    @Autowired
    private ThreadPoolBean threadPoolBean;
    @RequestMapping("/testbean")
    public Object getThreadBean() {
        return threadPoolBean;
    }

}

執行Application.java的main方法，
在瀏覽器裡輸入：http://localhost:8080/first/testbean
得到的返回值是：
{“maxThreads”:100,”minThreads”:8,”idleTimeout”:60000}

ok，fucking nice