SpringCloud集成了很多第三方框架，把它的全部源码拿出来解析几本书都讲不完，也不太现实，本文带领读者分析其中一小部分源码（其余源码读者有兴趣可以继续跟进），包括eureka-server、config、zuul的starter部分，分析其启动原理。
如果我们开发出一套框架，要和SpringBoot集成，就需要放到它的starter里。因此我们分析启动原理，直接从每个框架的starter开始分析即可。
Eureka-Server源码解析
我们知道，要实现注册与发现，需要在启动类加上@EnableEurekaServer注解，我们进入其源码：
@EnableDiscoveryClient//表示eurekaserver也是一个客户端服务
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(EurekaServerMarkerConfiguration.class)
public @interface EnableEurekaServer {
}
注意看@Import注解，这个注解导入了EurekaServerMarkerConfiguration类，继续跟进这个类：
/**
* Responsible for adding in a marker bean to activate
* {@link EurekaServerAutoConfiguration}
*
* @author Biju Kunjummen
*/
@Configuration
public class EurekaServerMarkerConfiguration {
@Bean
public Marker eurekaServerMarkerBean() {
return new Marker();
}
class Marker {
}
}
通过上面的注释，我们继续查看EurekaServerAutoConfiguration类的源码：
@Configuration
@Import(EurekaServerInitializerConfiguration.class)
@ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class)
@EnableConfigurationProperties({ EurekaDashboardProperties.class,
InstanceRegistryProperties.class })
@PropertySource("classpath:/eureka/server.properties")
public class EurekaServerAutoConfiguration extends WebMvcConfigurerAdapter {
/**
* List of packages containing Jersey resources required by the Eureka server
*/
private static String[] EUREKA_PACKAGES = new String[] { "com.netflix.discovery",
"com.netflix.eureka" };
@Autowired
private ApplicationInfoManager applicationInfoManager;
@Autowired
private EurekaServerConfig eurekaServerConfig;
@Autowired
private EurekaClientConfig eurekaClientConfig;
@Autowired
private EurekaClient eurekaClient;
@Autowired
private InstanceRegistryProperties instanceRegistryProperties;
public static final CloudJacksonJson JACKSON_JSON = new CloudJacksonJson();
@Bean
public HasFeatures eurekaServerFeature() {
return HasFeatures.namedFeature("Eureka Server",
EurekaServerAutoConfiguration.class);
}
//如果eureka.client.registerWithEureka=true，则把自己注册进去
@Configuration
protected static class EurekaServerConfigBeanConfiguration {
@Bean
@ConditionalOnMissingBean
public EurekaServerConfig eurekaServerConfig(EurekaClientConfig clientConfig) {
EurekaServerConfigBean server = new EurekaServerConfigBean();
if (clientConfig.shouldRegisterWithEureka()) {
// Set a sensible default if we are supposed to replicate
server.setRegistrySyncRetries(5);
}
return server;
}
}
//实例化eureka-server的界面
@Bean
@ConditionalOnProperty(prefix = "eureka.dashboard", name = "enabled", matchIfMissing = true)
public EurekaController eurekaController() {
return new EurekaController(this.applicationInfoManager);
}
static {
CodecWrappers.registerWrapper(JACKSON_JSON);
EurekaJacksonCodec.setInstance(JACKSON_JSON.getCodec());
}
@Bean
public ServerCodecs serverCodecs() {
return new CloudServerCodecs(this.eurekaServerConfig);
}
private static CodecWrapper getFullJson(EurekaServerConfig serverConfig) {
CodecWrapper codec = CodecWrappers.getCodec(serverConfig.getJsonCodecName());
return codec == null ? CodecWrappers.getCodec(JACKSON_JSON.codecName()) : codec;
}
private static CodecWrapper getFullXml(EurekaServerConfig serverConfig) {
CodecWrapper codec = CodecWrappers.getCodec(serverConfig.getXmlCodecName());
return codec == null ? CodecWrappers.getCodec(CodecWrappers.XStreamXml.class)
: codec;
}
class CloudServerCodecs extends DefaultServerCodecs {
public CloudServerCodecs(EurekaServerConfig serverConfig) {
super(getFullJson(serverConfig),
CodecWrappers.getCodec(CodecWrappers.JacksonJsonMini.class),
getFullXml(serverConfig),
CodecWrappers.getCodec(CodecWrappers.JacksonXmlMini.class));
}
}
@Bean
public PeerAwareInstanceRegistry peerAwareInstanceRegistry(
ServerCodecs serverCodecs) {
this.eurekaClient.getApplications(); // force initialization
return new InstanceRegistry(this.eurekaServerConfig, this.eurekaClientConfig,
serverCodecs, this.eurekaClient,
this.instanceRegistryProperties.getExpectedNumberOfRenewsPerMin(),
this.instanceRegistryProperties.getDefaultOpenForTrafficCount());
}
@Bean
@ConditionalOnMissingBean
public PeerEurekaNodes peerEurekaNodes(PeerAwareInstanceRegistry registry,
ServerCodecs serverCodecs) {
return new PeerEurekaNodes(registry, this.eurekaServerConfig,
this.eurekaClientConfig, serverCodecs, this.applicationInfoManager);
}
@Bean
public EurekaServerContext eurekaServerContext(ServerCodecs serverCodecs,
PeerAwareInstanceRegistry registry, PeerEurekaNodes peerEurekaNodes) {
return new DefaultEurekaServerContext(this.eurekaServerConfig, serverCodecs,
registry, peerEurekaNodes, this.applicationInfoManager);
}
@Bean
public EurekaServerBootstrap eurekaServerBootstrap(PeerAwareInstanceRegistry registry,
EurekaServerContext serverContext) {
return new EurekaServerBootstrap(this.applicationInfoManager,
this.eurekaClientConfig, this.eurekaServerConfig, registry,
serverContext);
}
/**
* Register the Jersey filter
*/
@Bean
public FilterRegistrationBean jerseyFilterRegistration(
javax.ws.rs.core.Application eurekaJerseyApp) {
FilterRegistrationBean bean = new FilterRegistrationBean();
bean.setFilter(new ServletContainer(eurekaJerseyApp));
bean.setOrder(Ordered.LOWEST_PRECEDENCE);
bean.setUrlPatterns(
Collections.singletonList(EurekaConstants.DEFAULT_PREFIX + "/*"));
return bean;
}
/**
* Construct a Jersey {@link javax.ws.rs.core.Application} with all the resources
* required by the Eureka server.
*/
@Bean
public javax.ws.rs.core.Application jerseyApplication(Environment environment,
ResourceLoader resourceLoader) {
ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(
false, environment);
// Filter to include only classes that have a particular annotation.
//
provider.addIncludeFilter(new AnnotationTypeFilter(Path.class));
provider.addIncludeFilter(new AnnotationTypeFilter(Provider.class));
// Find classes in Eureka packages (or subpackages)
//
Set> classes = new HashSet>();
for (String basePackage : EUREKA_PACKAGES) {
Set beans = provider.findCandidateComponents(basePackage);
for (BeanDefinition bd : beans) {
Class> cls = ClassUtils.resolveClassName(bd.getBeanClassName(),
resourceLoader.getClassLoader());
classes.add(cls);
}
}
// Construct the Jersey ResourceConfig
//
Map propsAndFeatures = new HashMap();
propsAndFeatures.put(
// Skip static content used by the webapp
ServletContainer.PROPERTY_WEB_PAGE_CONTENT_REGEX,
EurekaConstants.DEFAULT_PREFIX + "/(fonts|images|css|js)/.*");
DefaultResourceConfig rc = new DefaultResourceConfig(classes);
rc.setPropertiesAndFeatures(propsAndFeatures);
return rc;
}
@Bean
public FilterRegistrationBean traceFilterRegistration(
@Qualifier("webRequestLoggingFilter") Filter filter) {
FilterRegistrationBean bean = new FilterRegistrationBean();
bean.setFilter(filter);
bean.setOrder(Ordered.LOWEST_PRECEDENCE - 10);
return bean;
}
}
这个类上有一个注解：@ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class)，这后面指定的类就是刚才那个类，而@ConditionalOnBean这个注解的作用是：仅仅在当前上下文中存在某个对象时，才会实例化一个Bean。
因此，启动时就会实例化EurekaServerAutoConfiguration这个类。
@EnableConfigurationProperties({ EurekaDashboardProperties.class,
InstanceRegistryProperties.class })
这个注解就是定义了一些eureka的配置项。
Config源码解析
通过上面的方法，我们找到了ConfigServerAutoConfiguration类：
@Configuration
@ConditionalOnBean(ConfigServerConfiguration.Marker.class)
@EnableConfigurationProperties(ConfigServerProperties.class)
@Import({ EnvironmentRepositoryConfiguration.class, CompositeConfiguration.class, ResourceRepositoryConfiguration.class,
ConfigServerEncryptionConfiguration.class, ConfigServerMvcConfiguration.class, TransportConfiguration.class })
public class ConfigServerAutoConfiguration {
}
可以发现这个类是空的，只是多了几个注解，
@EnableConfigurationProperties(ConfigServerProperties.class)表示开启config配置属性。
最核心的注解是：@Import，他将其他一些配置类导入进这个类，其中：
EnvironmentRepositoryConfiguration：环境配置类，内置了以下几种环境配置：
1.Native
@Configuration
@Profile("native")
protected static class NativeRepositoryConfiguration {
@Autowired
private ConfigurableEnvironment environment;
@Bean
public NativeEnvironmentRepository nativeEnvironmentRepository() {
return new NativeEnvironmentRepository(this.environment);
}
}
2.git
@Configuration
@Profile("git")
protected static class GitRepositoryConfiguration extends DefaultRepositoryConfiguration {}
3.subversion
@Configuration
@Profile("subversion")
protected static class SvnRepositoryConfiguration {
@Autowired
private ConfigurableEnvironment environment;
@Autowired
private ConfigServerProperties server;
@Bean
public SvnKitEnvironmentRepository svnKitEnvironmentRepository() {
SvnKitEnvironmentRepository repository = new SvnKitEnvironmentRepository(this.environment);
if (this.server.getDefaultLabel()!=null) {
repository.setDefaultLabel(this.server.getDefaultLabel());
}
return repository;
}
}
4.vault
@Configuration
@Profile("subversion")
protected static class SvnRepositoryConfiguration {
@Autowired
private ConfigurableEnvironment environment;
@Autowired
private ConfigServerProperties server;
@Bean
public SvnKitEnvironmentRepository svnKitEnvironmentRepository() {
SvnKitEnvironmentRepository repository = new SvnKitEnvironmentRepository(this.environment);
if (this.server.getDefaultLabel()!=null) {
repository.setDefaultLabel(this.server.getDefaultLabel());
}
return repository;
}
}
//从代码可以看到Git是配置中心默认环境
@Bean
public MultipleJGitEnvironmentRepository defaultEnvironmentRepository() {
MultipleJGitEnvironmentRepository repository = new MultipleJGitEnvironmentRepository(this.environment);
repository.setTransportConfigCallback(this.transportConfigCallback);
if (this.server.getDefaultLabel()!=null) {
repository.setDefaultLabel(this.server.getDefaultLabel());
}
return repository;
}
我们进入MultipleJGitEnvironmentRepository类：
@ConfigurationProperties("spring.cloud.config.server.git")
public class MultipleJGitEnvironmentRepository extends JGitEnvironmentRepository {
}
这个类表示可以支持配置多个Git仓库，它继承自JGitEnvironmentRepository类：
public class JGitEnvironmentRepository extends AbstractScmEnvironmentRepository
implements EnvironmentRepository, SearchPathLocator, InitializingBean {
/**
* Get the working directory ready.
*/
public String refresh(String label) {
Git git = null;
try {
git = createGitClient();
if (shouldPull(git)) {
fetch(git, label);
// checkout after fetch so we can get any new branches, tags,
// ect.
checkout(git, label);
if (isBranch(git, label)) {
// merge results from fetch
merge(git, label);
if (!isClean(git)) {
logger.warn("The local repository is dirty. Resetting it to origin/" + label + ".");
resetHard(git, label, "refs/remotes/origin/" + label);
}
}
} else {
// nothing to update so just checkout
checkout(git, label);
}
// always return what is currently HEAD as the version
return git.getRepository().getRef("HEAD").getObjectId().getName();
} catch (RefNotFoundException e) {
throw new NoSuchLabelException("No such label: " + label, e);
} catch (NoRemoteRepositoryException e) {
throw new NoSuchRepositoryException("No such repository: " + getUri(), e);
} catch (GitAPIException e) {
throw new NoSuchRepositoryException("Cannot clone or checkout repository: " + getUri(), e);
} catch (Exception e) {
throw new IllegalStateException("Cannot load environment", e);
} finally {
try {
if (git != null) {
git.close();
}
} catch (Exception e) {
this.logger.warn("Could not close git repository", e);
}
}
}
}
refresh方法的作用就是configserver会从我们配置的git仓库拉取配置下来。
Zuul源码解析
同理，我们找到Zuul的配置类ZuulProxyAutoConfiguration：
@Configuration
@Import({ RibbonCommandFactoryConfiguration.RestClientRibbonConfiguration.class,
RibbonCommandFactoryConfiguration.OkHttpRibbonConfiguration.class,
RibbonCommandFactoryConfiguration.HttpClientRibbonConfiguration.class })
@ConditionalOnBean(ZuulProxyMarkerConfiguration.Marker.class)
public class ZuulProxyAutoConfiguration extends ZuulServerAutoConfiguration {
@SuppressWarnings("rawtypes")
@Autowired(required = false)
private List requestCustomizers = Collections.emptyList();
@Autowired
private DiscoveryClient discovery;
@Autowired
private ServiceRouteMapper serviceRouteMapper;
@Override
public HasFeatures zuulFeature() {
return HasFeatures.namedFeature("Zuul (Discovery)", ZuulProxyAutoConfiguration.class);
}
@Bean
@ConditionalOnMissingBean(DiscoveryClientRouteLocator.class)
public DiscoveryClientRouteLocator discoveryRouteLocator() {
return new DiscoveryClientRouteLocator(this.server.getServletPrefix(), this.discovery, this.zuulProperties,
this.serviceRouteMapper);
}
//以下是过滤器，也就是之前zuul提到的实现的ZuulFilter接口
// pre filters
//路由之前
@Bean
public PreDecorationFilter preDecorationFilter(RouteLocator routeLocator, ProxyRequestHelper proxyRequestHelper) {
return new PreDecorationFilter(routeLocator, this.server.getServletPrefix(), this.zuulProperties,
proxyRequestHelper);
}
// route filters
// 路由时
@Bean
public RibbonRoutingFilter ribbonRoutingFilter(ProxyRequestHelper helper,
RibbonCommandFactory> ribbonCommandFactory) {
RibbonRoutingFilter filter = new RibbonRoutingFilter(helper, ribbonCommandFactory, this.requestCustomizers);
return filter;
}
@Bean
@ConditionalOnMissingBean(SimpleHostRoutingFilter.class)
public SimpleHostRoutingFilter simpleHostRoutingFilter(ProxyRequestHelper helper, ZuulProperties zuulProperties) {
return new SimpleHostRoutingFilter(helper, zuulProperties);
}
@Bean
public ApplicationListener zuulDiscoveryRefreshRoutesListener() {
return new ZuulDiscoveryRefreshListener();
}
@Bean
@ConditionalOnMissingBean(ServiceRouteMapper.class)
public ServiceRouteMapper serviceRouteMapper() {
return new SimpleServiceRouteMapper();
}
@Configuration
@ConditionalOnMissingClass("org.springframework.boot.actuate.endpoint.Endpoint")
protected static class NoActuatorConfiguration {
@Bean
public ProxyRequestHelper proxyRequestHelper(ZuulProperties zuulProperties) {
ProxyRequestHelper helper = new ProxyRequestHelper();
helper.setIgnoredHeaders(zuulProperties.getIgnoredHeaders());
helper.setTraceRequestBody(zuulProperties.isTraceRequestBody());
return helper;
}
}
@Configuration
@ConditionalOnClass(Endpoint.class)
protected static class RoutesEndpointConfiguration {
@Autowired(required = false)
private TraceRepository traces;
@Bean
public RoutesEndpoint zuulEndpoint(RouteLocator routeLocator) {
return new RoutesEndpoint(routeLocator);
}
@Bean
public RoutesMvcEndpoint zuulMvcEndpoint(RouteLocator routeLocator, RoutesEndpoint endpoint) {
return new RoutesMvcEndpoint(endpoint, routeLocator);
}
@Bean
public ProxyRequestHelper proxyRequestHelper(ZuulProperties zuulProperties) {
TraceProxyRequestHelper helper = new TraceProxyRequestHelper();
if (this.traces != null) {
helper.setTraces(this.traces);
}
helper.setIgnoredHeaders(zuulProperties.getIgnoredHeaders());
helper.setTraceRequestBody(zuulProperties.isTraceRequestBody());
return helper;
}
}
private static class ZuulDiscoveryRefreshListener implements ApplicationListener {
private HeartbeatMonitor monitor = new HeartbeatMonitor();
@Autowired
private ZuulHandlerMapping zuulHandlerMapping;
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof InstanceRegisteredEvent) {
reset();
}
else if (event instanceof ParentHeartbeatEvent) {
ParentHeartbeatEvent e = (ParentHeartbeatEvent) event;
resetIfNeeded(e.getValue());
}
else if (event instanceof HeartbeatEvent) {
HeartbeatEvent e = (HeartbeatEvent) event;
resetIfNeeded(e.getValue());
}
}
private void resetIfNeeded(Object value) {
if (this.monitor.update(value)) {
reset();
}
}
private void reset() {
this.zuulHandlerMapping.setDirty(true);
}
}
}
通过@Import注解可以找到几个类：
RibbonCommandFactoryConfiguration.RestClientRibbonConfiguration、RibbonCommandFactoryConfiguration.OkHttpRibbonConfiguration、RibbonCommandFactoryConfiguration.HttpClientRibbonConfiguration
我们知道zuul提供网关能力，通过上面这几个类就能分析到，它内部其实也是通过接口请求，找到每个服务提供的接口地址。
进入RibbonCommandFactoryConfiguration类：
public class RibbonCommandFactoryConfiguration {
//以下提供了3个不同的请求模式
@Configuration
@ConditionalOnRibbonRestClient
protected static class RestClientRibbonConfiguration {
@Autowired(required = false)
private Set zuulFallbackProviders = Collections.emptySet();
@Bean
@ConditionalOnMissingBean
public RibbonCommandFactory> ribbonCommandFactory(
SpringClientFactory clientFactory, ZuulProperties zuulProperties) {
return new RestClientRibbonCommandFactory(clientFactory, zuulProperties,
zuulFallbackProviders);
}
}
@Configuration
@ConditionalOnRibbonOkHttpClient
@ConditionalOnClass(name = "okhttp3.OkHttpClient")
protected static class OkHttpRibbonConfiguration {
@Autowired(required = false)
private Set zuulFallbackProviders = Collections.emptySet();
@Bean
@ConditionalOnMissingBean
public RibbonCommandFactory> ribbonCommandFactory(
SpringClientFactory clientFactory, ZuulProperties zuulProperties) {
return new OkHttpRibbonCommandFactory(clientFactory, zuulProperties,
zuulFallbackProviders);
}
}
@Configuration
@ConditionalOnRibbonHttpClient
protected static class HttpClientRibbonConfiguration {
@Autowired(required = false)
private Set zuulFallbackProviders = Collections.emptySet();
@Bean
@ConditionalOnMissingBean
public RibbonCommandFactory> ribbonCommandFactory(
SpringClientFactory clientFactory, ZuulProperties zuulProperties) {
return new HttpClientRibbonCommandFactory(clientFactory, zuulProperties, zuulFallbackProviders);
}
}
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnRibbonHttpClientCondition.class)
@interface ConditionalOnRibbonHttpClient { }
private static class OnRibbonHttpClientCondition extends AnyNestedCondition {
public OnRibbonHttpClientCondition() {
super(ConfigurationPhase.PARSE_CONFIGURATION);
}
@Deprecated //remove in Edgware"
@ConditionalOnProperty(name = "zuul.ribbon.httpclient.enabled", matchIfMissing = true)
static class ZuulProperty {}
@ConditionalOnProperty(name = "ribbon.httpclient.enabled", matchIfMissing = true)
static class RibbonProperty {}
}
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnRibbonOkHttpClientCondition.class)
@interface ConditionalOnRibbonOkHttpClient { }
private static class OnRibbonOkHttpClientCondition extends AnyNestedCondition {
public OnRibbonOkHttpClientCondition() {
super(ConfigurationPhase.PARSE_CONFIGURATION);
}
@Deprecated //remove in Edgware"
@ConditionalOnProperty("zuul.ribbon.okhttp.enabled")
static class ZuulProperty {}
@ConditionalOnProperty("ribbon.okhttp.enabled")
static class RibbonProperty {}
}
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnRibbonRestClientCondition.class)
@interface ConditionalOnRibbonRestClient { }
private static class OnRibbonRestClientCondition extends AnyNestedCondition {
public OnRibbonRestClientCondition() {
super(ConfigurationPhase.PARSE_CONFIGURATION);
}
@Deprecated //remove in Edgware"
@ConditionalOnProperty("zuul.ribbon.restclient.enabled")
static class ZuulProperty {}
@ConditionalOnProperty("ribbon.restclient.enabled")
static class RibbonProperty {}
}
}
总结
前面带领大家分析了一小段源码，SpringCloud很庞大，不可能一一分析，文本的主要目的就是教大家如何分析源码，从何处下手，以便大家可以按照这种思路继续跟踪下去。
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