IoC容器的设计（利用反射、注解和工厂模式实现）

package org.example; import org.example.Annotations.Autowired; import org.example.Annotations.Component; import org.example.Annotations.ComponentScan; import org.example.Annotations.Configuration; import org.springframework.core.io.Resource; import org.springframework.core.io.support.PathMatchingResourcePatternResolver; import org.springframework.core.type.classreading.SimpleMetadataReaderFactory; import javax.swing.plaf.IconUIResource; import java.lang.annotation.Annotation; import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.util.HashMap; import java.util.Map; public class AnnotationApplicationContext implements ApplicationContext { //定义Map，用于存放bean对象 private Map<String, Object> beanFactory = new HashMap<>(); //创建IOC容器类时执行的方法 public AnnotationApplicationContext(Class configClass) throws InstantiationException, IllegalAccessException { //处理@Configuration的逻辑（没有实质性的内容，只是要求必须有配置类） try { //获取@Configuration类型的对象 Configuration configuration = (Configuration) configClass.getAnnotation(Configuration.class); //如果对象为空，则引发异常 if (configuration.annotationType().toGenericString().equals("")) { //没有具体逻辑 } } catch (Exception e) { System.out.println("找不到配置类"); System.exit(-1); } //处理@ComponentScan的逻辑 /* 总的来说，就是扫描某一路径下的所有类，如果有的类被Component注解，则创建其实例（一个bean），加入beanFactory中 如果有的类中的对象（一个Field类型的数据）被@Autowired注解标注，则用beanFactory中同类型的bean替代该对象 */ try { ComponentScan componentScan = (ComponentScan) configClass.getAnnotation(ComponentScan.class); //根据componentScanValue的值来获取要扫描的路径 String componentScanValue = componentScan.value().toString(); String path = ""; if (!componentScanValue.equals("")) { String[] splitValue = componentScanValue.split("\\."); for (int i = 0; i < splitValue.length; i++) { path += splitValue[i] + "/"; } path = "classpath*:" + path + "**/*.class"; } else { path = "classpath*:org/example/**/*.class"; } //扫描路径，获取所有的class PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver(); Resource[] resources = resolver.getResources(path); for (Resource res : resources) { //获取类名 String clsName = new SimpleMetadataReaderFactory().getMetadataReader(res).getClassMetadata().getClassName(); //获取类对象 Class thisClass = Class.forName(clsName); //判断当前类是否被Component注解标注 Component component = (Component) thisClass.getAnnotation(Component.class); if (component != null) //说明该类被Component注解标注 { Constructor c = thisClass.getConstructor(); Object o = c.newInstance(); //创建该类的实例 beanFactory.put(o.getClass().getSimpleName(), o);//加入beanFactory中 } //处理@Autowired注解 for (Object bean : beanFactory.values()) { //查看beanFactory中所有的bean Class beanClass = bean.getClass(); Field[] beanFields = beanClass.getDeclaredFields(); //获取bean的fields for (Field field : beanFields) { if (field.isAnnotationPresent(Autowired.class)) { //如果被Autowired注解标注 Object beanD = beanFactory.get(field.getType().getSimpleName()); //获取beanFactory中的bean field.setAccessible(true); //关闭安全检查 field.set(bean, beanD); //用beanFactory中的bean来代替当前bean } } } } } catch (Exception e) { e.printStackTrace(); System.out.println("没有ComponentScan注解"); System.exit(-1); } // Field[] configFields = configClass.getDeclaredFields(); // //处理标注为Bean的逻辑 @Component注解处理 // for (Field field : configFields) { // if (field.isAnnotationPresent(Component.class)) // { // Object beanComponent = field.getType().newInstance(); // beanFactory.put(field.getType().getSimpleName(),beanComponent); // } // } // //处理自动注入的逻辑 @Autowired处理 // for (Object bean:beanFactory.values()) // { // Class beanClass = bean.getClass(); // Field[] beanFields = beanClass.getDeclaredFields(); // for (Field field : beanFields) // { // if (field.isAnnotationPresent(Autowired.class)) // { // Object beanD = beanFactory.get(field.getType().getSimpleName()); // field.setAccessible(true); // field.set(bean,beanD); // } // } // } } //getBean方法，获取某个bean（通过class） @Override public Object getBean(Class beanClass) { return beanFactory.get(beanClass.getSimpleName()); } }