手撕spring框架（4）
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手撕spring框架（1）
手撕spring框架（2）
手撕spring框架（3）
本节主要是讲通过BeanNameAware获取在容器中配置的Bean名称，使得Bean能够获取自身在容器中的标识。
简介
BeanNameAware接口在spring中是一个回调接口，它提供了一个用于设置Bean名称的方法。当一个Bean实现了BeanNameWaare接口时，在该Bean实例被实例化后，Spring容器会调用setBeanName方法，并将该Bean在Spring容器中的名称作为参数传递过去。
以下是示例代码：
package com.spring;public interface BeanNameAware {void setBeanName(String beanName);
}
使用
在UserService类中实现BeanNameAware中的setBeanName方法，源码如下：
package com.dzend.service;import com.spring.Autowired;
import com.spring.BeanNameAware;
import com.spring.Component;@Component(value = "userService")
public class UserService implements UserInterface, BeanNameAware {private String beanName;@Autowiredprivate OrderService orderService;@DzendValue("xxxxx")private String test;@Overridepublic void test() {System.out.println(test);}public OrderService getOrderService() {return orderService;}@Overridepublic void setBeanName(String beanName) {this.beanName = beanName;}
}
调整DzendApplicationContext类中的createBean方法，在BeanPostProcessor初始化下加下以下代码：
if(instance instanceof BeanNameAware){((BeanNameAware) instance).setBeanName(beanName);
}
最后DzendApplicationContext代码如下:
package com.spring;import java.beans.Introspector;
import java.io.File;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.net.URL;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;public class DzendApplicationContext {private Class<?> configClass;private Map<String,BeanDefinition> beanDefinitionMap= new HashMap<>();private Map<String, Object> singletonObjects=new HashMap<>();private List<BeanPostProcessor> beanPostProcessorList = new ArrayList<>();public DzendApplicationContext(Class configClass) {this.configClass=configClass;scan(configClass);}private void scan(Class configClass) {if(configClass.isAnnotationPresent(ComponentScan.class)){ComponentScan componentScan = (ComponentScan) configClass.getAnnotation(ComponentScan.class);String path = componentScan.value();path = path.replace(".","/");ClassLoader classLoader = DzendApplicationContext.class.getClassLoader();URL resource = classLoader.getResource(path);try {path = URLDecoder.decode(path, "UTF-8");} catch (UnsupportedEncodingException e) {throw new RuntimeException(e);}File file = null;try {file = new File( URLDecoder.decode(resource.getFile(), "UTF-8"));} catch (UnsupportedEncodingException e) {throw new RuntimeException(e);}if(file.isDirectory()){for (File f : file.listFiles()) {String absolutePath = f.getAbsolutePath();absolutePath = absolutePath.substring(absolutePath.indexOf("com"),absolutePath.indexOf(".class"));absolutePath=absolutePath.replace("\\",".");try {Class<?> clazz = classLoader.loadClass(absolutePath);if (clazz.isAnnotationPresent(Component.class)) {if (BeanPostProcessor.class.isAssignableFrom(clazz)) {BeanPostProcessor instance = (BeanPostProcessor) clazz.getConstructor().newInstance();beanPostProcessorList.add(instance);}Component componentAnnotaion = clazz.getAnnotation(Component.class);String beanName= componentAnnotaion.value();if("".equals(beanName)){beanName = Introspector.decapitalize(clazz.getSimpleName());}BeanDefinition beanDefinition = new BeanDefinition();beanDefinition.setType(clazz);if (clazz.isAnnotationPresent(Scope.class)) {Scope scopeAnnotation = clazz.getAnnotation(Scope.class);String value = scopeAnnotation.value();beanDefinition.setScope(value);}else{beanDefinition.setScope("singleton");}beanDefinitionMap.put(beanName,beanDefinition);}} catch (ClassNotFoundException e) {e.printStackTrace();} catch (InvocationTargetException e) {throw new RuntimeException(e);} catch (InstantiationException e) {throw new RuntimeException(e);} catch (IllegalAccessException e) {throw new RuntimeException(e);} catch (NoSuchMethodException e) {throw new RuntimeException(e);}}}}}public Object getBean(String beanName){if(!beanDefinitionMap.containsKey(beanName)){throw new NullPointerException();}BeanDefinition beanDefinition = beanDefinitionMap.get(beanName);if(beanDefinition.getScope().equals("singleton")){Object singletonObject = singletonObjects.get(beanName);if(singletonObject == null){singletonObject = createBean(beanName,beanDefinition);singletonObjects.put(beanName,singletonObject);}return singletonObject;}else{//原型Object prototypeBean = createBean(beanName, beanDefinition);return prototypeBean;}}private Object createBean(String beanName, BeanDefinition beanDefinition) {Class clazz = beanDefinition.getType();Object instance = null;try {instance = clazz.getConstructor().newInstance();for (Field field : clazz.getDeclaredFields()) {if(field.isAnnotationPresent(Autowired.class)){field.setAccessible(true);field.set(instance,getBean(field.getName()));}}for (BeanPostProcessor beanPostProcessor : beanPostProcessorList) {instance = beanPostProcessor.postProcessBeforeInitialization(instance,beanName);}if(instance instanceof BeanNameAware){((BeanNameAware) instance).setBeanName(beanName);}if(instance instanceof InitializingBean){((InitializingBean) instance).afterPropertiesSet();}for (BeanPostProcessor beanPostProcessor : beanPostProcessorList) {instance = beanPostProcessor.postProcessAfterInitialization(instance,beanName);}} catch (InstantiationException e) {throw new RuntimeException(e);} catch (IllegalAccessException e) {throw new RuntimeException(e);} catch (InvocationTargetException e) {throw new RuntimeException(e);} catch (NoSuchMethodException e) {throw new RuntimeException(e);}return instance;}
}
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