1、初步构造
1、实例化过程初始化了 ApplicationContextInitializer 和 ApplicationListener ,同时判断了当前是否处于 web 环境中
//SpringApplication.java 257
//1.根据 { "javax.servlet.Servlet",
// "org.springframework.web.context.ConfigurableWebApplicationContext" } 是否存在, 决定web环境
this.webEnvironment = deduceWebEnvironment();
//2.加载所有的 ApplicationContextInitializer (META-INF/spring.factories)
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
//3.加载所有的 ApplicationListener (META-INF/spring.factories)
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
//4.定义 main 方法
this.mainApplicationClass = deduceMainApplicationClass();
2、核心文件 META-INF/spring.factories ,使用 SpringFactoriesLoader.loadFactoryNames(type, classLoader) 读取
//SpringFactoriesLoader.java 109行
//读取 "META-INF/spring.factories" 文件
Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) : ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
while (urls.hasMoreElements()) {
URL url = urls.nextElement();
Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));
String factoryClassNames = properties.getProperty(factoryClassName);
result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(
factoryClassNames)));
}
2、启动过程
1、开启时间记录
StopWatch stopWatch = new StopWatch();
stopWatch.start();
//...省略
stopWatch.stop();
2、初始化所有监听器 ,使用一个类来管理所有的监听器,负责发布所有的事件
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.started();
//getRunListeners 方法,读取的也是上面的文件,加载所有的 SpringApplicationRunListener
return new SpringApplicationRunListeners(logger, getSpringFactoriesInstances(
SpringApplicationRunListener.class, types, this, args));
3、 配置环境 environment
//1.启动参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
//2.此处配置的是 StandardServletEnvironment,并合并启动参数到环境中,并发布 SpringApplicationRunListeners 事件
ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);
4、打印 banner
Banner printedBanner = printBanner(environment);
5、创建容器,并预处理容器
//1.创建的是 AnnotationConfigEmbeddedWebApplicationContext
context = createApplicationContext();
prepareContext(context, environment, listeners, applicationArguments,printedBanner);
//1.设置 environment
context.setEnvironment(environment);
//2.调用所有的 ApplicationContextInitializer
applyInitializers(context);
//3.发布 SpringApplicationRunListeners 事件
listeners.contextPrepared(context);
//4.注册当前 Application 类到容器中
load(context, sources.toArray(new Object[sources.size()]));
//5.发布 SpringApplicationRunListeners 事件
listeners.contextLoaded(context);
6、刷新容器,其实执行的就是 refresh
//1.最终调用的是 AbstractApplicationContext 的 refresh 方法
refreshContext(context);
7、调用 runners
//调用 ApplicationRunner 和 CommandLineRunner 的 run 方法,可以用来启动其他的服务
List<Object> runners = new ArrayList<Object>();
runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
AnnotationAwareOrderComparator.sort(runners);
for (Object runner : new LinkedHashSet<Object>(runners)) {
if (runner instanceof ApplicationRunner) {
callRunner((ApplicationRunner) runner, args);
}
if (runner instanceof CommandLineRunner) {
callRunner((CommandLineRunner) runner, args);
}
}
3、@Configuration 注解加载过程
1、加载过程,使用的是 ConfigurationClassPostProcessor 类来进行处理的
//1.获取所有的bean
String[] candidateNames = registry.getBeanDefinitionNames();
for(...){
//2.判断对应bean是否为配置类,如果是,则加入到configCandidates
}
//3.对configCandidates 进行 排序,按照@Order 配置的值进行排序
Collections.sort(configCandidates, new Comparator<BeanDefinitionHolder>() {
@Override
public int compare(BeanDefinitionHolder bd1, BeanDefinitionHolder bd2) {
int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
return (i1 < i2) ? -1 : (i1 > i2) ? 1 : 0;
}
});
//4.调用ConfigurationClassParser#parse进行解析
parser.parse(candidates);
parser.validate();
//5.将解析过的配置类加入到configClasses,并去重
Set<ConfigurationClass> configClasses = new LinkedHashSet<ConfigurationClass>(parser.getConfigurationClasses());
configClasses.removeAll(alreadyParsed);
//6.解析bean
this.reader.loadBeanDefinitions(configClasses);
2、@Configuration 注解类的解析过程
//ConfigurationClassBeanDefinitionReader.java 124行
//1.解析每个方法,寻找 @Bean 注解
for (BeanMethod beanMethod : configClass.getBeanMethods()) {
loadBeanDefinitionsForBeanMethod(beanMethod);
}
//2.解析 import 标签,按照 xml 方式去解析 bean
loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
4、@Import 注解加载过程
1、ConfigurationClassPostProcessor 在 调用 ConfigurationClassParser.parse 中去解析的
public void parse(Set<BeanDefinitionHolder> configCandidates) {
//...省略
processDeferredImportSelectors();
}
2、举例:@EnableAutoConfiguration
该注解使用到了 @Import(EnableAutoConfigurationImportSelector.class)
public String[] selectImports(AnnotationMetadata metadata) {
if (!isEnabled(metadata)) {
return NO_IMPORTS;
}
try {
AnnotationAttributes attributes = getAttributes(metadata);
//1.读取 META-INF/spring.factories 文件下所有 EnableAutoConfiguration 类型的类
List<String> configurations = getCandidateConfigurations(metadata,attributes);
configurations = removeDuplicates(configurations);
Set<String> exclusions = getExclusions(metadata, attributes);
configurations.removeAll(exclusions);
configurations = sort(configurations);
recordWithConditionEvaluationReport(configurations, exclusions);
return configurations.toArray(new String[configurations.size()]);
}
catch (IOException ex) {
throw new IllegalStateException(ex);
}
}
3、@import 使用的几种方式
- 最简单的方式,直接将类引入
@Configuration
@Import(value={UserServiceImpl.class})
public class Config {}
- 使用 ImportBeanDefinitionRegistrar 方式
public class UserServiceBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata,
BeanDefinitionRegistry registry) {
//通过registry就可以注入到容器里
}
}
- 使用 @ImportSelector 方式
@Configuration()
@Import(UserServiceImportSelect.class)
public class Config {
}
public class UserServiceImportSelect implements ImportSelector{
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
}
}