SpringBoot 中 AutoConfiguration的使用方法

更新時(shí)間：2019年04月12日 11:00:21 作者：small_925_ant

這篇文章主要介紹了SpringBoot 中 AutoConfiguration的使用方法，本文通過(guò)實(shí)例代碼給大家介紹的非常詳細(xì)，具有一定的參考借鑒價(jià)值,需要的朋友可以參考下

在SpringBoot中我們經(jīng)?？梢砸胍恍﹕tarter包來(lái)集成一些工具的使用,比如spring-boot-starter-data-redis。

使用起來(lái)很方便,那么是如何實(shí)現(xiàn)的呢?

代碼分析

我們先看注解@SpringBootApplication,它里面包含一個(gè)@EnableAutoConfiguration

繼續(xù)看@EnableAutoConfiguration注解

@Import({AutoConfigurationImportSelector.class})

在這個(gè)類(AutoConfigurationImportSelector)里面實(shí)現(xiàn)了自動(dòng)配置的加載

主要代碼片段:

String[] selectImports(AnnotationMetadata annotationMetadata)方法中

AutoConfigurationImportSelector.AutoConfigurationEntry autoConfigurationEntry = this.getAutoConfigurationEntry(autoConfigurationMetadata, annotationMetadata);

getAutoConfigurationEntry方法中:

List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes); 

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
    List<String> configurations = SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());
    Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct.");
    return configurations;
}

最后會(huì)通過(guò)SpringFactoriesLoader.loadSpringFactories去加載META-INF/spring.factories

Enumeration<URL> urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories");
        LinkedMultiValueMap result = new LinkedMultiValueMap();

    while(urls.hasMoreElements()) {
          URL url = (URL)urls.nextElement();
          UrlResource resource = new UrlResource(url);
          Properties properties = PropertiesLoaderUtils.loadProperties(resource);
          Iterator var6 = properties.entrySet().iterator();

          while(var6.hasNext()) {
            Entry<?, ?> entry = (Entry)var6.next();
            String factoryClassName = ((String)entry.getKey()).trim();
            String[] var9 = StringUtils.commaDelimitedListToStringArray((String)entry.getValue());
            int var10 = var9.length;

            for(int var11 = 0; var11 < var10; ++var11) {
              String factoryName = var9[var11];
              result.add(factoryClassName, factoryName.trim());
            }
          }
        }

ZookeeperAutoConfiguration

我們來(lái)實(shí)現(xiàn)一個(gè)ZK的AutoConfiguration

首先定義一個(gè)ZookeeperAutoConfiguration類

然后在META-INF/spring.factories中加入

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.fayayo.fim.zookeeper.ZookeeperAutoConfiguration

接下來(lái)我們看看具體的實(shí)現(xiàn):

@ConfigurationProperties(prefix = "fim.register")
@Configuration
public class URLRegistry {
  private String address;
  private int timeout;
  private int sessionTimeout;
  public String getAddress() {
    if (address == null) {
      address = URLParam.ADDRESS;
    }
    return address;
  }
  public void setAddress(String address) {
    this.address = address;
  }
  public int getTimeout() {
    if (timeout == 0) {
      timeout = URLParam.CONNECTTIMEOUT;
    }
    return timeout;
  }
  public void setTimeout(int timeout) {
    this.timeout = timeout;
  }
  public int getSessionTimeout() {
    if (sessionTimeout == 0) {
      sessionTimeout = URLParam.REGISTRYSESSIONTIMEOUT;
    }
    return sessionTimeout;
  }
  public void setSessionTimeout(int sessionTimeout) {
    this.sessionTimeout = sessionTimeout;
  }
}
@Configuration
@EnableConfigurationProperties(URLRegistry.class)
@Slf4j
public class ZookeeperAutoConfiguration {
  @Autowired
  private URLRegistry url;
  @Bean(value = "registry")
  public Registry createRegistry() {
    try {
      String address = url.getAddress();
      int timeout = url.getTimeout();
      int sessionTimeout = url.getSessionTimeout();
      log.info("init ZookeeperRegistry,address[{}],sessionTimeout[{}],timeout[{}]", address, timeout, sessionTimeout);
      ZkClient zkClient = new ZkClient(address, sessionTimeout, timeout);
      return new ZookeeperRegistry(zkClient);
    } catch (ZkException e) {
      log.error("[ZookeeperRegistry] fail to connect zookeeper, cause: " + e.getMessage());
      throw e;
    }
  }
}

ZookeeperRegistry部分實(shí)現(xiàn):

public ZookeeperRegistry(ZkClient zkClient) {
    this.zkClient = zkClient;

    log.info("zk register success!");

    String parentPath = URLParam.ZOOKEEPER_REGISTRY_NAMESPACE;
    try {
      if (!zkClient.exists(parentPath)) {
        log.info("init zookeeper registry namespace");
        zkClient.createPersistent(parentPath, true);
      }
      //監(jiān)聽
      zkClient.subscribeChildChanges(parentPath, new IZkChildListener() {
        //對(duì)父節(jié)點(diǎn)添加監(jiān)聽子節(jié)點(diǎn)變化。
        @Override
        public void handleChildChange(String parentPath, List<String> currentChilds) {
          log.info(String.format("[ZookeeperRegistry] service list change: path=%s, currentChilds=%s", parentPath, currentChilds.toString()));
          if(watchNotify!=null){
            watchNotify.notify(nodeChildsToUrls(currentChilds));
          }
        }
      });

      ShutDownHook.registerShutdownHook(this);

    } catch (Exception e) {
      e.printStackTrace();
      log.error("Failed to subscribe zookeeper");
    }
  }

具體使用

那么我們?cè)趺词褂米约簩懙腪ookeeperAutoConfiguration呢

首先要在需要使用的項(xiàng)目中引入依賴

   <dependency>
      <groupId>com.fayayo</groupId>
      <artifactId>fim-registry-zookeeper</artifactId>
      <version>0.0.1-SNAPSHOT</version>
    </dependency>

然后配置參數(shù)

 fim:
   register:
    address: 192.168.88.129:2181
    timeout: 2000

如果不配置會(huì)有默認(rèn)的參數(shù)

具體使用的時(shí)候只需要在Bean中注入就可以了,比如

@Autowired
  private Registry registry;
  public List<URL> getAll(){
    List<URL>list=cache.get(KEY);
    if(CollectionUtils.isEmpty(list)){
      list=registry.discover();
      cache.put(KEY,list);
    }
    return list;
  }

完整代碼

https://github.com/lizu18xz/fim.git

總結(jié)

以上所述是小編給大家介紹的SpringBoot 中 AutoConfiguration的使用方法，希望對(duì)大家有所幫助，如果大家有任何疑問請(qǐng)給我留言，小編會(huì)及時(shí)回復(fù)大家的。在此也非常感謝大家對(duì)腳本之家網(wǎng)站的支持！
如果你覺得本文對(duì)你有幫助，歡迎轉(zhuǎn)載，煩請(qǐng)注明出處，謝謝！

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