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本章节通过手写一个简单的 Spring 框架来加深对 Spring 框架源码以及设计思想的理解#xff1b;
实现步骤
BeanScope 枚举代码
public enum BeanScope { sigleton, prototype;
}AppConfig 配置类
// 定义包扫描路径
ComponentScan(com.dufu.spring
实现步骤
BeanScope 枚举代码
public enum BeanScope { sigleton, prototype;
}AppConfig 配置类
// 定义包扫描路径
ComponentScan(com.dufu.spring)
public class AppConfig {}DufuBeanPostProcessor 后置处理器
Component
public class DufuBeanPostProcessor implements BeanPostProcessor {Overridepublic Object postProcessorBeforeInitialization(String beanName, Object bean) {if (beanName.equals(userService)) {System.out.println(处理 userService 初始化之前 ...);}return bean;}Overridepublic Object postProcessorAfterInitialization(String beanName, Object bean) {if (beanName.equals(userService)) {System.out.println(处理 userService 初始化之后 ...);// 创建代理对象模拟 AOP 功能Object proxyInstance Proxy.newProxyInstance(DufuBeanPostProcessor.class.getClassLoader(),bean.getClass().getInterfaces(), new InvocationHandler() {Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {System.out.println(AOP 切面逻辑 ...);return method.invoke(bean, args);}});return proxyInstance;}return bean;}UserService 接口代码
public interface IUserService { void test();
}OrderService 实例
Component
public class OrderService {}UserService 实例
Component
public class UserService implements BeanNameAware, InitializingBean, IUserService {Autowiredprivate OrderService orderService;public void print() {System.out.println(orderService);}Overridepublic void setBeanName(String beanName) {System.out.println(beanName beanName);}Overridepublic void afterPropertiesSet() {System.out.println(UserService 初始化后其他操作 ...);}Overridepublic void test() {System.out.println(调用了 test() 方法);}
}Autowired 注解
Retention(RetentionPolicy.RUNTIME)
Target(ElementType.FIELD)
public interface Autowired {String value() default ;
}
BeanDefinition Bean 的定义工具类
public class BeanDefinition {// Bean 的类型private Class type;// Bean 的范围(多例还是单例)private String scope;public Class getType() {return type;}public void setType(Class type) {this.type type;}public String getScope() {return scope;}public void setScope(String scope) {this.scope scope;}
}BeanNameAware 回调接口
public interface BeanNameAware { void setBeanName(String beanName);
}BeanPostProcessor 后置处理器接口
public interface BeanPostProcessor { // 初始化前 Object postProcessorBeforeInitialization(String beanName, Object bean); // 初始化后 Object postProcessorAfterInitialization(String beanName, Object bean);
}Component 注解
Retention(RetentionPolicy.RUNTIME)
Target(ElementType.TYPE)
public interface Component {String value() default ;
}ComponentScan 注解
Retention(RetentionPolicy.RUNTIME)
Target(ElementType.TYPE)
public interface ComponentScan {String value() default ;
}DufuApplicationContext Spring 容器核心设计
public class DufuApplicationContext {// 点符号private final String SYMBOL_SPOT .;// 左斜线private final String LEFT_SLASH /;// 右斜线private final String RIGHT_SLASH \\;// .class 后缀private final String SUFFIX_CLASS .class;// 配置类private Class configClass;// Bean 信息集合private ConcurrentHashMap String, BeanDefinition beanDefinitionMap new ConcurrentHashMap ();// Bean 单例池private ConcurrentHashMap String, Object singletonObjects new ConcurrentHashMap ();// 后置处理器集合private List BeanPostProcessor beanPostProcessorList new ArrayList ();public DufuApplicationContext() {}public DufuApplicationContext(Class configClass) throws Exception {this.configClass configClass;// 判断有没有 ComponentScan 注解, 并获取扫描路径解析 Bean 对象信息if (configClass.isAnnotationPresent(ComponentScan.class)) {ComponentScan componentScanAnnotation (ComponentScan) configClass.getAnnotation(ComponentScan.class);String pkScanValue componentScanAnnotation.value().equals() ? configClass.getPackage().getName() : componentScanAnnotation.value();// 注意: 我们实际上需要的是 out 目录下的路径String packagePath pkScanValue.replace(SYMBOL_SPOT, LEFT_SLASH);ClassLoader classLoader DufuApplicationContext.class.getClassLoader();URL resource classLoader.getResource(packagePath);// 得到本地项目的绝对路径// D:\sorftware\idea\workspace\workspace_11\spring-dufu\out\production\spring-dufu\com\dufu\serviceFile outDirectory new File(resource.getFile());if (outDirectory.isDirectory()) {// 拿到所有编译后的 class 文件File[] files outDirectory.listFiles();for (File file: files) {String filePath file.getAbsolutePath();if (filePath.endsWith(SUFFIX_CLASS)) {String className filePath.substring(filePath.lastIndexOf(RIGHT_SLASH) 1, filePath.lastIndexOf(SUFFIX_CLASS));Class ? clazz classLoader.loadClass(pkScanValue SYMBOL_SPOT className);// 记录后置处理器if (BeanPostProcessor.class.isAssignableFrom(clazz)) {BeanPostProcessor instance (BeanPostProcessor) clazz.newInstance();beanPostProcessorList.add(instance);}// 声明为 Bean 的实体类if (clazz.isAnnotationPresent(Component.class)) {Component componentAnnotation clazz.getAnnotation(Component.class);// 获取 BeanNameString beanName componentAnnotation.value().equals() ? Introspector.decapitalize(clazz.getSimpleName()) : componentAnnotation.value();// 定义 BeanBeanDefinition beanDefinition new BeanDefinition();// 定义 Bean 的类型beanDefinition.setType(clazz);// 定义 Bean 的范围if (clazz.isAnnotationPresent(Scope.class)) {Scope scopeAnnotation clazz.getAnnotation(Scope.class);beanDefinition.setScope(scopeAnnotation.value());} else { // 单例 BeanbeanDefinition.setScope(BeanScope.sigleton.toString());}// 将定义后的 Bean 存入到单例池beanDefinitionMap.put(beanName, beanDefinition);}}}}}// 实例化单例 Beanfor (String beanName: beanDefinitionMap.keySet()) {BeanDefinition beanDefinition beanDefinitionMap.get(beanName);if (beanDefinition.getScope().equals(BeanScope.sigleton.toString())) {Object bean createBean(beanName, beanDefinition);singletonObjects.put(beanName, bean);}}}/*** 创建 Bean 对象*/private Object createBean(String beanName, BeanDefinition beanDefinition) throws Exception {Class clazz beanDefinition.getType();// 利用初始化方法实例化对象Object instance clazz.getConstructor().newInstance();// 依赖注入for (Field field: clazz.getDeclaredFields()) {// 如果属性上添加了 Autowired 注解就注入if (field.isAnnotationPresent(Autowired.class)) {field.setAccessible(true);field.set(instance, getBean(field.getName()));}}// 如果实现了 BeanNameAware 接口, 回调方法if (instance instanceof BeanNameAware) {((BeanNameAware) instance).setBeanName(beanName);}// 后置处理器, 初始化前for (BeanPostProcessor beanPostProcessor: beanPostProcessorList) {instance beanPostProcessor.postProcessorBeforeInitialization(beanName, instance);}// 初始化if (instance instanceof InitializingBean) {((InitializingBean) instance).afterPropertiesSet();}// BeanPostProcessor(Bean 的后置处理器) 初始化后 AOP// 后置处理器, 初始化后for (BeanPostProcessor beanPostProcessor: beanPostProcessorList) {instance beanPostProcessor.postProcessorAfterInitialization(beanName, instance);}return instance;}/*** 根据名称获取 Bean*/public Object getBean(String beanName) throws Exception {BeanDefinition beanDefinition beanDefinitionMap.get(beanName);if (null beanDefinition) {throw new NullPointerException(名为: beanName 的 Bean 不存在);}String scope beanDefinition.getScope();if (scope.equals(BeanScope.sigleton.toString())) { // 单例 BeanObject bean singletonObjects.get(beanName);if (null bean) {singletonObjects.put(beanName, createBean(beanName, beanDefinition));}return bean;} else { // 多例 Beanreturn createBean(beanName, beanDefinition);}}
}InitializingBean 初始化 Bean 接口
public interface InitializingBean { void afterPropertiesSet();
}Scope 注解
Retention(RetentionPolicy.RUNTIME)
Target(ElementType.TYPE)
public interface Scope { String value() default ;
}测试一下
public class Test {public static void main(String[] args) throws Exception {DufuApplicationContext context new DufuApplicationContext(AppConfig.class);// 模拟依赖注入Aware 回调初始化//UserService userService (UserService)context.getBean(userService);//System.out.println(userService);//userService.print();// 模拟 AOP 功能调用前需要先注释掉上面的代码IUserService iUserService (IUserService) context.getBean(userService);iUserService.test();}
}
