项目实战：组件扫描(3)-装配bean之间的依赖关系

基于Java反射的ComponentScan组件扫描与依赖注入,

原创于 2023-11-08 14:54:44 发布 · 235 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#java #getType #stream #filter #find #findFirst #orElseThrow

IOC_MVC 专栏收录该内容

21 篇文章

订阅专栏

文章讲述了如何使用ComponentScan进行Java类的自动扫描，并在beanFactory中实例化对象，同时处理依赖注入的过程，涉及Spring框架中的注解如@Controller,@Service,@Repository。

1、ComponentScan

package com.csdn.mymvc.core;
import com.csdn.mymvc.annotation.Autowire;
import com.csdn.mymvc.annotation.Controller;
import com.csdn.mymvc.annotation.Repository;
import com.csdn.mymvc.annotation.Service;
import java.io.File;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.util.*;
public class ComponentScan {
    public static Map<String, Object> beanFactory = new HashMap<>();
    static String path = null;
    static {
        //分析文件夹
        path = ComponentScan.class.getClassLoader().getResource("").getPath();
        //  /F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/
        //  pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/
        //计算机的硬盘根目录是 / ，不论是什么操作系统。只是微软人为的分出盘符的概念
        //System.out.println(path);
        path = path.substring(1);
        //System.out.println(path);
        //   F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target
        //   /pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/
        File rootDir = new File(path);
        //开始解析文件夹 - 组件扫描工作开始
        try {
            //第 1 步：扫描类路径，解析出所有的bean实例，存放到IOC容器中(beanFactory)
            parseFile(rootDir);
            beanFactory.values().forEach(System.out::println);
            //第 2 步：经过第 1 步，所有的bean实例已经创建就绪，但是bean和bean之间的依赖关系没有注入(Injection)
            //本步骤实现 注入依赖关系
            beanFactory.values().forEach(bean -> {
                //获取bean内部所有的field
                Field[] fields = bean.getClass().getDeclaredFields();
                //获取每一个field上的注解信息
                Arrays.stream(fields)
                        .filter(field -> field.getDeclaredAnnotation(Autowire.class) != null)
                        .forEach(field -> {
                            //获取这个字段的类型的名称
                            String fieldTypeName = field.getType().getName();
                            System.out.println(fieldTypeName);
                            Object filedValue = beanFactory.values().stream().filter(instance -> {
                                return field.getType().isAssignableFrom(instance.getClass());
                            }).findFirst().orElseThrow(() -> new RuntimeException(fieldTypeName + "装配失败！"));

                            try {
                                field.setAccessible(true);
                                field.set(bean, filedValue);
                            } catch (IllegalAccessException e) {
                                throw new RuntimeException(e);
                            }
                        });
            });


            System.out.println(beanFactory);


        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (InvocationTargetException e) {
            throw new RuntimeException(e);
        } catch (NoSuchMethodException e) {
            throw new RuntimeException(e);
        } catch (InstantiationException e) {
            throw new RuntimeException(e);
        } catch (IllegalAccessException e) {
            throw new RuntimeException(e);
        }
    }
    private static void parseFile(File file) throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException {
        if (file.exists()) {
            if (file.isDirectory()) {
                //获取所有的子目录
                File[] childFiles = file.listFiles();
                for (File childFile : childFiles) {
                      parseFile(childFile);
                }
            } else {
                String absPath = file.getAbsolutePath();
                //System.out.println(absPath);
                String fullClassPath = absPath.substring(path.length());
                //System.out.println(fullClassPath);
                if (fullClassPath.endsWith(".class")) {
                    String fullClassPathName = fullClassPath.substring(0, fullClassPath.length() - ".class".length());
                    //System.out.println(fullClassPathName);
                    String fullClassName = fullClassPathName.replaceAll("\\\\", ".");
                    //System.out.println(fullClassName);
                    Class<?> clazz = Class.forName(fullClassName);
                    //System.out.println(clazz.toString());
                    if (clazz.toString().startsWith("class")) {  //排除掉接口、注解....,只关心class

                        if (!Modifier.isAbstract(clazz.getModifiers())) {   //排除掉抽象类

                            Optional<Annotation> optional = Arrays.stream(clazz.getDeclaredAnnotations()).filter(annotation -> {
                                return (annotation instanceof Controller || annotation instanceof Service || annotation instanceof Repository);
                            }).findFirst();

                            if (!optional.isEmpty()) {
                                Object bean = clazz.getDeclaredConstructor().newInstance();
                                beanFactory.put(fullClassName, bean);
                            }
                        }
                    }
                }
            }
        }
    }
}

2、beanFactory.values().forEach(System.out::println);

com.csdn.fruit.servlet.FruitController@269378a1
com.csdn.fruit.service.impl.FruitServiceImpl@74f9e47d
com.csdn.fruit.dao.impl.FruitDaoImpl@d171ccd