nosum-spring/src/main/java/cn/nosum/framework/context/ApplicationContext.java

package cn.nosum.framework.context;

import cn.nosum.framework.annotation.Autowired;
import cn.nosum.framework.annotation.Controller;
import cn.nosum.framework.annotation.Service;
import cn.nosum.framework.beans.BeanDefinition;
import cn.nosum.framework.beans.BeanWrapper;
import cn.nosum.framework.beans.support.BeanDefinitionReader;

import java.lang.reflect.Field;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;

public class ApplicationContext {
    protected final Map<String, BeanDefinition> beanDefinitionMap=new ConcurrentHashMap<String, BeanDefinition>();
    private String[] configLocations;
    private BeanDefinitionReader reader;

    private Map<String,Object> factoryBeanObjectCache=new ConcurrentHashMap<String, Object>();
    private Map<String, BeanWrapper> factoryBeanInstanceCache=new ConcurrentHashMap<String, BeanWrapper>();

    public ApplicationContext(String... configLocations){
        this.configLocations=configLocations;
        try {
            // 定位
            reader=new BeanDefinitionReader(this.configLocations);
            // 加载配置文件，扫描相关的类，包装为 BeanDefinition
            List<BeanDefinition>beanDefinitions=reader.loadBeanDefinitions();
            // 注册，将配置信息放到容器中
            doRegistryBeanDefinition(beanDefinitions);
            // 依赖注入
            doAutowired();
        }catch (Exception e){e.printStackTrace();}
    }

    private void doRegistryBeanDefinition(List<BeanDefinition> beanDefinitions) throws Exception {
        for (BeanDefinition beanDefinition : beanDefinitions) {
            if (this.beanDefinitionMap.containsKey(beanDefinition.getFactoryBeanName())){
                throw new Exception("The Bean " + beanDefinition.getFactoryBeanName() + "is exists!!");
            }
            this.beanDefinitionMap.put(beanDefinition.getFactoryBeanName(),beanDefinition);
            this.beanDefinitionMap.put(beanDefinition.getBeanClassName(),beanDefinition);
        }
    }

    private void doAutowired() {
        for (Map.Entry<String, BeanDefinition> beanDefinitionEntry : this.beanDefinitionMap.entrySet()) {
            String beanName=beanDefinitionEntry.getKey();
            try {
                getBean(beanName);
            }catch (Exception e){e.printStackTrace();}
        }
    }

    private Object getBean(Class<?> beanClass) {
        return getBean(beanClass.getName());
    }

    private Object getBean(String beanName) {
        // 读取配置信息
        BeanDefinition beanDefinition=this.beanDefinitionMap.get(beanName);
        // 将对象封装到 BeanDefinitionWrapper 中
        BeanWrapper beanWrapper=new BeanWrapper(instantiateBean(beanDefinition));
        // 缓存
        this.factoryBeanInstanceCache.put(beanName,beanWrapper);
        // 依赖注入
        populateBean(beanName,beanDefinition,beanWrapper);
        return this.factoryBeanInstanceCache.get(beanName).getWrapperInstance();
    }

    private void populateBean(String beanName, BeanDefinition beanDefinition, BeanWrapper beanWrapper) {
        //可能涉及到循环依赖？
        //A{ B b}
        //B{ A b}
        //用两个缓存，循环两次
        //1、把第一次读取结果为空的BeanDefinition存到第一个缓存
        //2、等第一次循环之后，第二次循环再检查第一次的缓存，再进行赋值
        Object instance = beanWrapper.getWrapperInstance();
        Class<?> clazz = beanWrapper.getWrappedClass();
        //在Spring中@Component
        if(!(clazz.isAnnotationPresent(Controller.class) || clazz.isAnnotationPresent(Service.class))){
            return;
        }
        //把所有的包括private/protected/default/public 修饰字段都取出来
        for (Field field : clazz.getDeclaredFields()) {
            if(!field.isAnnotationPresent(Autowired.class)){ continue; }
            Autowired autowired = field.getAnnotation(Autowired.class);
            //如果用户没有自定义的beanName，就默认根据类型注入
            String autowiredBeanName = autowired.value().trim();
            if("".equals(autowiredBeanName)){
                //field.getType().getName() 获取字段的类型
                autowiredBeanName = field.getType().getName();
            }
            //暴力访问
            field.setAccessible(true);
            try {
                if(this.factoryBeanInstanceCache.get(autowiredBeanName) == null){
                    continue;
                }
                field.set(instance,this.factoryBeanInstanceCache.get(autowiredBeanName).getWrapperInstance());
            } catch (IllegalAccessException e) {
                e.printStackTrace();
                continue;
            }
        }

    }

    private Object instantiateBean(BeanDefinition beanDefinition) {
        // 取得实例化对象的类名
        String className=beanDefinition.getBeanClassName();
        Object instance=null;
        try{
            if (this.factoryBeanObjectCache.containsKey(className)){
                instance=this.factoryBeanObjectCache.get(className);
            }else{
                Class<?> clazz=Class.forName(className);
                instance=clazz.getDeclaredConstructor().newInstance();
                this.factoryBeanObjectCache.put(className,instance);
                this.factoryBeanObjectCache.put(beanDefinition.getFactoryBeanName(),instance);
            }
        }catch (Exception e){e.printStackTrace();}
        return instance;
    }

    public String[] getBeanDefinitionNames(){
        return this.beanDefinitionMap.keySet().toArray(new String[getBeanDefinitionCount()]);
    }

    public int getBeanDefinitionCount(){
        return this.beanDefinitionMap.size();
    }

   public Properties getConfig(){
        return this.reader.getConfig();
   }

}