Java面试知识总结.zip

package com.southeast.ioc.factory; import com.southeast.BeanPostProcessor; import com.southeast.ioc.bean.BeanDefinition; import com.southeast.ioc.bean.BeanReference; import com.southeast.ioc.bean.PropertyValue; import com.southeast.ioc.bean.PropertyValues; import com.southeast.ioc.xml.XmlBeanDefinitionReader; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; /** * Created by 18351 on 2019/1/17. */ public class XmlBeanFactory implements BeanFactory{ private Map<String, BeanDefinition> beanDefinitionMap = new HashMap<>(); private List<String> beanDefinitionNames = new ArrayList<>(); // 用来存储注册的BeanPostProcessor private List<BeanPostProcessor> beanPostProcessors = new ArrayList<>(); private XmlBeanDefinitionReader beanDefinitionReader; //初始化的时候，自动装配属性 public XmlBeanFactory(String location) throws Exception { beanDefinitionReader = new XmlBeanDefinitionReader(); loadBeanDefinitions(location); } private void loadBeanDefinitions(String location) throws Exception { beanDefinitionReader.loadBeanDefinitions(location); registerBeanDefinition(); registerBeanPostProcessor(); } /** * 注册BeanDefinition */ private void registerBeanDefinition() { //获取从xml文件中读取到的信息 Map<String, BeanDefinition> map=beanDefinitionReader.getRegistry(); for(String name:map.keySet()){ BeanDefinition beanDefinition=map.get(name); beanDefinitionMap.put(name,beanDefinition); beanDefinitionNames.add(name); } } /** * 注册BeanPostProcessor */ public void registerBeanPostProcessor() throws Exception { List beans = getBeansForType(BeanPostProcessor.class); for (Object bean : beans) { addBeanPostProcessor((BeanPostProcessor) bean); } } /** * 注册BeanPostProcessor * 1. 根据 BeanDefinition 记录的信息，寻找所有实现了 BeanPostProcessor 接口的类。 * 2. 实例化 BeanPostProcessor 接口的实现类 * 3. 将实例化好的对象放入 List中 */ public List getBeansForType(Class type) throws Exception { List beans = new ArrayList<>(); for (String beanDefinitionName : beanDefinitionNames) { if (type.isAssignableFrom(beanDefinitionMap.get(beanDefinitionName).getBeanClass())) { beans.add(getBean(beanDefinitionName)); } } return beans; } //将beanPostProcessor放入容器中 public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) { beanPostProcessors.add(beanPostProcessor); } /** * getBean 简化方案 */ @Override public Object getBean(String name) throws Exception { BeanDefinition beanDefinition = beanDefinitionMap.get(name); if (beanDefinition == null) { throw new IllegalArgumentException("no this bean with name " + name); } //根据beanDefiniton获取Bean Object bean = beanDefinition.getBean(); if (bean == null) { //1. 实例化 Bean 对象 //2.将配置文件中配置的属性注入到新创建的 Bean 对象中 //3 .检查 Bean 对象是否实现了 Aware 一类的接口，如果实现了则把相应的依赖设置到 Bean 对象中。 bean = createBean(beanDefinition); //4. 调用 BeanPostProcessor 前置处理方法，即 postProcessBeforeInitialization(Object bean, String beanName) //5. 调用 BeanPostProcessor 后置处理方法，即 postProcessAfterInitialization(Object bean, String beanName) bean = initializeBean(bean, name); beanDefinition.setBean(bean); } return bean; } private Object createBean(BeanDefinition bd) throws Exception { //1. 实例化 Bean 对象 Object bean = bd.getBeanClass().newInstance(); // 2. 将配置文件中配置的属性注入到新创建的 Bean 对象中 applyPropertyValues(bean, bd); return bean; } private void applyPropertyValues(Object bean, BeanDefinition bd) throws Exception { //3 .检查 Bean 对象是否实现了 Aware 一类的接口，如果实现了则把相应的依赖设置到 Bean 对象中。 if (bean instanceof BeanFactoryAware) { ((BeanFactoryAware) bean).setBeanFactory(this); } PropertyValues propertyValues=bd.getPropertyValues(); for (PropertyValue propertyValue : propertyValues.getPropertyValues()) { Object value = propertyValue.getValue(); if (value instanceof BeanReference) { BeanReference beanReference = (BeanReference) value; value = getBean(beanReference.getName()); } //保证了使用 set方法为对象注入属性 try { Method declaredMethod = bean.getClass().getDeclaredMethod( "set" + propertyValue.getName().substring(0, 1).toUpperCase() + propertyValue.getName().substring(1), value.getClass()); declaredMethod.setAccessible(true); //执行 setter方法 declaredMethod.invoke(bean, value); } catch (NoSuchMethodException e) { Field declaredField = bean.getClass().getDeclaredField(propertyValue.getName()); declaredField.setAccessible(true); //创建 setter declaredField.set(bean, value); } } } private Object initializeBean(Object bean, String name) throws Exception { //4. 调用 BeanPostProcessor 前置处理方法，即 postProcessBeforeInitialization(Object bean, String beanName) for (BeanPostProcessor beanPostProcessor : beanPostProcessors) { bean = beanPostProcessor.postProcessBeforeInitialization(bean, name); } //5. 调用 BeanPostProcessor 后置处理方法，即 postProcessAfterInitialization(Object bean, String beanName) for (BeanPostProcessor beanPostProcessor : beanPostProcessors) { bean = beanPostProcessor.postProcessAfterInitialization(bean, name); } return bean; } }