SpringBoot容器
1.@Configuration
告诉SpringBoot这是配置文件
@Configuration(proxyBeanMethods = true)
public class MyConfig {
@Bean//默认也是单实例的
public User user1()
{
return new User("ylc",22);
}
}
里面包含默认值proxyBeanMethods参数
proxyBeanMethods:代理bean的方法
- Full模式:proxyBeanMethods = true,通过方法调用依然指向原来的bean
- Lite模式:proxyBeanMethods = false,直接返回新实例对象
组件依赖(有二次调用)必须使用Full模式默认。其他默认是否Lite模式
/*这是一个Springboot应用*/
@SpringBootApplication(scanBasePackages = "com.ylc")
public class MainApplication {
public static void main(String[] args) {
//返回IOC容器
ConfigurableApplicationContext context = SpringApplication.run(MainApplication.class,args);
//从容器中获取组件
User user1 = context.getBean("user1", User.class);
User user2 = context.getBean("user1", User.class);
System.out.println(user1==user2);
}
}
最后为结果为true
不需要创建新组件时使用Lite模式,创建新组件时使用Full模式保证取得的组件为ioc中同一组件
2.@Import
@Import(DBHelper.class)//给容器中自动创建出这类型的组件、默认组件的名字就是全类名
3.@Condictional
条件装配:满足Conditional指定的条件才可以注入
例如@ConditionalOnBean
,在有某个bean的时候才会注入
如果注入b的时候需要依赖a那么它们直接就可以使用条件装配,这个发生在bean的注入之前
如果把该注解放在类上,不满足条件整个类里面包含的东西都不会注册到,存在先后顺序
4.@ImportResource
用于导入外部资源文件
@ImportResource("classpath:beans.xml")
5.@ConfigurationProperties
用于配置文件绑定
user.name="小明"
user.age=12
5.1@Component+@ConfigurationProperties
只有这个组件是容器中的组件,才能使用容器提供的@ConfigurationProperties功能
@Component
@ConfigurationProperties(prefix = "user")//user为配置文件的前缀名
public class User {
public String name;
public int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public User(String name, int age) {
this.name = name;
this.age = age;
}
public User() {
}
}
@RestController
public class HelloWorldController {
@Autowired
User user;
@RequestMapping("/GetUser")
public User GetUser()
{
return user;
}
}
5.2 @EnableConfigurationProperties+@ConfigurationProperties
@EnableConfigurationProperties(Car.class)
//1、开启Car配置绑定功能
//2、把这个Car这个组件自动注册到容器中
public class MyConfig {
}
@ConfigurationProperties(prefix = "mycar")
public class Car {
public String CarType;
public int Price;
public Car(String carType, int price) {
CarType = carType;
Price = price;
}
public String getCarType() {
return CarType;
}
public void setCarType(String carType) {
CarType = carType;
}
public double getPrice() {
return Price;
}
public void setPrice(int price) {
Price = price;
}
public Car() {
}
}
6.@SpringBootApplication
@SpringBootApplication是一个合成注解,实际由以下注解组成
6.1 @SpringBootConfiguration
@SpringBootConfiguration
包含@Configuration注解表明这是一个配置类
6.2 @EnableAutoConfiguration(重要)
自动载入应用程序所需的所有Bean
@EnableAutoConfiguration
包含以下注解
6.2.1@AutoConfigurationPackage
将指定包下的所有组件导入进来,默认MainApplication类所在的包下
里面包含@Import({Registrar.class})
利用Registrar
给容器中导入一系列组件
static class Registrar implements ImportBeanDefinitionRegistrar, DeterminableImports {
public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
AutoConfigurationPackages.register(registry, (String[])(new AutoConfigurationPackages.PackageImports(metadata)).getPackageNames().toArray(new String[0]));
}
}
metadata
把注解源信息拿出来,然后通过getPackageNames
获取包名,把包名封装到数组里面,最后注册信息
6.2.2 @Import({AutoConfigurationImportSelector.class})
给容器中导入一个组件
AutoConfigurationImportSelector
类里面包含selectImports
方法,String[]最后用于存储要导入的包
public String[] selectImports(AnnotationMetadata annotationMetadata) {
if (!this.isEnabled(annotationMetadata)) {
return NO_IMPORTS;
} else {
AutoConfigurationImportSelector.AutoConfigurationEntry autoConfigurationEntry = this.getAutoConfigurationEntry(annotationMetadata);
return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
}
}
其中getAutoConfigurationEntry
方法,获取所有自动配置的集合
protected AutoConfigurationImportSelector.AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {
if (!this.isEnabled(annotationMetadata)) {
return EMPTY_ENTRY;
} else {
AnnotationAttributes attributes = this.getAttributes(annotationMetadata);
//获取所有候选的配置 然后将配置过滤 去重,最后再封装
List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);
configurations = this.removeDuplicates(configurations);
Set<String> exclusions = this.getExclusions(annotationMetadata, attributes);
this.checkExcludedClasses(configurations, exclusions);
configurations.removeAll(exclusions);
configurations = this.getConfigurationClassFilter().filter(configurations);
this.fireAutoConfigurationImportEvents(configurations, exclusions);
return new AutoConfigurationImportSelector.AutoConfigurationEntry(configurations, exclusions);
}
}
//获取所有候选的配置
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;
}
其中loadFactoryNames
方法,利用工厂加载得到的所有组件
public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) {
ClassLoader classLoaderToUse = classLoader;
if (classLoader == null) {
classLoaderToUse = SpringFactoriesLoader.class.getClassLoader();
}
String factoryTypeName = factoryType.getName();
return (List)loadSpringFactories(classLoaderToUse).getOrDefault(factoryTypeName, Collections.emptyList());
}
loadSpringFactories
这里搜索所有META-INF/spring.factories配置文件,将根据@EnableAutoConfiguration的完整类名org.springframework.boot.autoconfigure.EnableAutoConfiguration作为查找的Key,获取对应的一组@Configuration类,存储再Map中
private static Map<String, List<String>> loadSpringFactories(ClassLoader classLoader) {
Enumeration urls = classLoader.getResources("META-INF/spring.factories");
}
从META-INF/spring.factories的位置来加载一个配置文件,默认扫描当前系统里面所有的信息
在spring-boot-autoconfigure-2.5.3.jar 包中的spring.factories文件中写死了SpringBoot启动要加载的所有配置
虽然所有自动配置启动的时候默认全部加载
xxxxAutoConfiguration 按照条件装配规则(@Conditional),最终会按需配置
6.3 @ComponentScan
@ComponentScan的功能其实就是自动扫描并加载符合条件的组件(比如@Component和@Repository等)或者bean定义,最终将这些bean定义加载到IoC容器中