image.png

package com.erik.spring;

import java.io.File;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationTargetException;
import java.net.URL;
import java.util.Enumeration;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

public class ErikApplicationContext {

    private Class aClass;

    private ConcurrentMap<String, BeanDeinition> concurrentMap = new ConcurrentHashMap<>();
    private ConcurrentMap<String, Object> concurrentSingleMap = new ConcurrentHashMap<>();
    public ErikApplicationContext(Class aClass) throws IOException, ClassNotFoundException, InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException {
        this.aClass = aClass;
        // 扫描
        if (aClass.isAnnotationPresent(ComponentScan.class)) {
            ClassLoader loader = aClass.getClassLoader();
            ComponentScan annotation = (ComponentScan) aClass.getAnnotation(ComponentScan.class);
            String value = annotation.value();
            String replace = value.replace(".", "/");
            URL resource = loader.getResource(replace);
            File file = new File(resource.getFile());
            if (file.isDirectory()) {
                File[] files = file.listFiles();
                for (File file1 : files) {
                    if (file1.getName().endsWith(".class")) {
                        String s = file1.getName().replace(".class", "");
                        String newV = value + "." + s;
                        System.out.println(newV);
                        Class<?> loadClass = loader.loadClass(newV);
                        // 判断是否含有Component注解
                        if (loadClass.isAnnotationPresent(Component.class)) {
                            Component component = loadClass.getAnnotation(Component.class);
                            String value1 = component.value();
                            BeanDeinition deinition = new BeanDeinition();
                            String scope = "";
                            if (loadClass.isAnnotationPresent(Scope.class)) {
                                scope = loadClass.getAnnotation(Scope.class).value();
                            }else {
                                scope = "singleton";
                            }
                            deinition.setScope(scope);
                            deinition.setType(loadClass);
                            concurrentMap.put(value1, deinition);
                        }
                    }
                }
            }
        }

        // 获取所有的单例对象，封装起来
        for (String s : concurrentMap.keySet()) {
            BeanDeinition deinition = concurrentMap.get(s);
            if (deinition.getScope().equals("singleton")) {
                if (concurrentSingleMap.get(s) == null) {
                    Object bena = createBena(s, deinition);
                    concurrentSingleMap.put(s, bena);
                }
            }
        }
    }

    private Object createBena(String beanName, BeanDeinition beanDeinition) throws NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException {
        Class type = beanDeinition.getType();
        return type.getConstructor().newInstance();
    }

    public Object getBean(String beanName) throws InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException {

        BeanDeinition o = concurrentMap.get(beanName);
        if (o == null) {
            throw new NullPointerException();
        }
        if (o.getScope().equals("singleton")) {
            return concurrentSingleMap.get(beanName);
        }
        // 创建
        return createBena(beanName, o);
    }
}