接上一篇[探究spring的底层实现原理1
上一篇从理论到源码讲到了以下四点
BeanFactory
Bean的整个生命周期
Bean的属性填充
依赖注入
这节就切合上一篇,手写一个简易版spring的小demo,看看我是怎样去实现的java
<谨供参考>
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| ClassPathXmlApplicationContext:xml配置文件方式
AH8q3dGK2f2vLZVgbRfLTjQPySe2yRaJHs:注解方式
SpringApplication:SpringBoot方式
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模拟注解方式启动
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| @ComponentScan("org.xiaowu.xiaowu.spring.xiaowu")
public class AppConfig {
}
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- 标注@Component的类则是需要被spring管理的
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| @Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public [@interface](https:
String value() default "";
}
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@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Scope {
Mode value() default Mode.SINGLETON;
}
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- BeanDefinition 描述了一个 Bean 实例，实例包含属性值、构造方法参数值以及更多实现信息.这里我放了俩参数,scope和claszz
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@Getter
@Setter
public class BeanDefinition {
private Class clazz;
private Mode scope;
}
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- 等同spring的BeanPostProcessor.在初始化bean前后使用
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@Component
public class BeanPostProcessorImpl implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) {
if (beanName.equals("userService")){
((UserService)bean).setName("我是小五");
}
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) {
if (beanName.equals("userService")) {
Object proxyInstance = Proxy.newProxyInstance(BeanPostProcessorImpl.class.getClassLoader(), bean.getClass().getInterfaces(), new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
return method.invoke(bean,args);
}
});
return proxyInstance;
}
return bean;
}
}
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- 等同spring的InitializingBean
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public interface InitializingBean {
void afterPropertiesSet();
}
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public class AH8q3dGK2f2vLZVgbRfLTjQPySe2yRaJHs {
private Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(16);
private Map<String, Object> singleTonMap = new ConcurrentHashMap<>(16);
private List<BeanPostProcessor> beanPostProcessors = new ArrayList<>(16);
public AH8q3dGK2f2vLZVgbRfLTjQPySe2yRaJHs(Class configClazz) throws Exception {
if (configClazz.isAnnotationPresent(ComponentScan.class)) {
ComponentScan componentScan = (ComponentScan) configClazz.getDeclaredAnnotation(ComponentScan.class);
String path = componentScan.value();
ClassLoader classLoader = AH8q3dGK2f2vLZVgbRfLTjQPySe2yRaJHs.class.getClassLoader();
String filePath = StrUtil.replace(path, ".", "/");
URL url = classLoader.getResource(filePath);
List<String> recursiveFiles = new ArrayList<>();
RecursiveFileUtils.recursiveFiles(url.getFile(),recursiveFiles);
for (String absolutePath : recursiveFiles) {
String subPath = StrUtil.sub(absolutePath, absolutePath.indexOf(path), absolutePath.lastIndexOf(".class"));
Class<?> aClass = classLoader.loadClass(subPath);
if (aClass.isAnnotationPresent(Component.class)) {
if (BeanPostProcessor.class.isAssignableFrom(aClass)){
BeanPostProcessor beanPostProcessor = (BeanPostProcessor) aClass.getDeclaredConstructor().newInstance();
beanPostProcessors.add(beanPostProcessor);
}
Component componentAnnotation = aClass.getDeclaredAnnotation(Component.class);
String beanName = StrUtil.isEmpty(componentAnnotation.value()) ? StrUtil.lowerFirst(aClass.getSimpleName()) : componentAnnotation.value();
BeanDefinition beanDefinition = new BeanDefinition();
beanDefinition.setClazz(aClass);
if (aClass.isAnnotationPresent(Scope.class)) {
Scope scopeAnnotation = aClass.getDeclaredAnnotation(Scope.class);
beanDefinition.setScope(scopeAnnotation.value());
} else {
beanDefinition.setScope(Mode.SINGLETON);
}
beanDefinitionMap.put(beanName, beanDefinition);
}
}
for (String beanName : beanDefinitionMap.keySet()) {
BeanDefinition beanDefinition = beanDefinitionMap.get(beanName);
if (beanDefinition.getScope() == Mode.SINGLETON) {
Object bean = singleTonMap.get(beanName);
if (!Optional.ofNullable(bean).isPresent()){
bean = createBean(beanName,beanDefinition);
singleTonMap.put(beanName, bean);
}
}
}
} else {
throw new RuntimeException("未被标注");
}
}
private Object createBean(String beanName,BeanDefinition beanDefinition) {
try {
Class clazz = beanDefinition.getClazz();
Object newInstance = clazz.getDeclaredConstructor().newInstance();
for (Field declaredField : clazz.getDeclaredFields()) {
if (declaredField.isAnnotationPresent(Autowired.class)) {
Object bean = getBean(declaredField.getName());
if (!Optional.ofNullable(bean).isPresent()){
throw new RuntimeException("getBean "+beanName+" 错误");
}
declaredField.setAccessible(true);
declaredField.set(newInstance, bean);
}
}
for (BeanPostProcessor beanPostProcessor : beanPostProcessors) {
beanPostProcessor.postProcessBeforeInitialization(newInstance,beanName);
}
if (newInstance instanceof InitializingBean){
((InitializingBean)newInstance).afterPropertiesSet();
}
for (BeanPostProcessor beanPostProcessor : beanPostProcessors) {
beanPostProcessor.postProcessAfterInitialization(newInstance,beanName);
}
singleTonMap.put(beanName, newInstance);
return newInstance;
} catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
e.printStackTrace();
}
return null;
}
public Object getBean(String beanName) {
BeanDefinition beanDefinition = beanDefinitionMap.get(beanName);
if (beanDefinition != null) {
if (beanDefinition.getScope() == Mode.SINGLETON) {
Object bean = singleTonMap.get(beanName);
return Optional.ofNullable(bean).isPresent()?bean:createBean(beanName,beanDefinition);
} else {
return createBean(beanName,beanDefinition);
}
}
throw new RuntimeException("未找到当前bean对象");
}
}
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测试一下看看
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@Component
@Scope(Mode.SINGLETON)
public class UserService implements InitializingBean {
@Autowired
private OrderService orderService;
@Setter
@Getter
private String name;
public void test(){
System.out.println(orderService);
System.out.println(name);
}
@Override
public void afterPropertiesSet() {
System.out.println("执行afterPropertiesSet方法");
}
}
public class XiaowuSpringApplication {
public static void main(String[] args) throws Exception {
AH8q3dGK2f2vLZVgbRfLTjQPySe2yRaJHs annotationConfigApplicationContext = new AH8q3dGK2f2vLZVgbRfLTjQPySe2yRaJHs(AppConfig.class);
UserService userService = (UserService) annotationConfigApplicationContext.getBean("userService");
userService.test();
}
}
执行afterPropertiesSet方法
org.xiaowu.xiaowu.spring.xiaowu.service.OrderService@5474c6c
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源码仓库地址: 简易版spring demo
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