在SpringBoot中我们经常可以引入一些starter包来集成一些工具的使用,比如spring-boot-starter-data-redis。
使用起来很方便,那么是如何实现的呢?
代码分析
我们先看注解@SpringBootApplication,它里面包含一个@EnableAutoConfiguration
继续看@EnableAutoConfiguration注解
@Import({AutoConfigurationImportSelector.class})
在这个类(AutoConfigurationImportSelector)里面实现了自动配置的加载
主要代码片段:
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;
}
最后会通过SpringFactoriesLoader.loadSpringFactories去加载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
我们来实现一个ZK的AutoConfiguration
首先定义一个ZookeeperAutoConfiguration类
然后在META-INF/spring.factories中加入
org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.fayayo.fim.zookeeper.ZookeeperAutoConfiguration
接下来我们看看具体的实现:
@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部分实现:
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);
}
//监听
zkClient.subscribeChildChanges(parentPath, new IZkChildListener() {
//对父节点添加监听子节点变化。
@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");
}
}
具体使用
那么我们怎么使用自己写的ZookeeperAutoConfiguration呢
首先要在需要使用的项目中引入依赖
<dependency>
<groupId>com.fayayo</groupId>
<artifactId>fim-registry-zookeeper</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
然后配置参数
fim:
register:
address: 192.168.88.129:2181
timeout: 2000
如果不配置会有默认的参数
具体使用的时候只需要在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;
}
完整代码
https://github.com/lizu18xz/fim.git
总结
以上所述是小编给大家介绍的SpringBoot 中 AutoConfiguration的使用方法，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！
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