仿写简单IOC

待我称王封你为后i 2024-03-26 19:24 35阅读 0赞

**目录**

TestController类:

UserService类:

核心代码SpringIOC：

Autowired和Component注解

SpringIOCTest 类

编辑

总结：

--------------------

![2f27ad00343b4454940d5753678bdaa0.png][]

#### **TestController类:** ####

@Component
    public class TestController {
    
        @Autowired
        private UserService userService;
    
        public void test(){
         userService.addUser("我口袋只剩玫瑰一片","此行又山高路远");
        }
    }

#### UserService类: ####

@Component
    public class UserService {
    
        public void addUser(String a,String b){
            System.out.println(a);
            System.out.println(b);
        }
    }

#### 核心代码SpringIOC： ####

public class SpringIOC {
        private List<String> beanNames;
        private List<String> filePaths;
        private String basePath;
        private String basePackage;
    
        private Map<String, Object> beans =new HashMap<>();
        /**
         * 扫描所有的文件信息信息，存到了 filePaths
         */
        private void scan() throws FileNotFoundException {
            File file = new File(basePath);
            filePaths = new ArrayList<>();
            if(file.exists()){
                Queue<File> queue = new LinkedList<>();
                queue.add(file);
                while(!queue.isEmpty()){
                    File poll = queue.poll();
                    if(poll == null){
                        continue;
                    }
                    if(poll.isDirectory()){
                        File[] files = poll.listFiles();
                        for (File f : files) {
                            queue.add(f);
                        }
                    }else {
                        filePaths.add(poll.getPath());
                    }
                }
            }else {
                throw new FileNotFoundException(basePath+" not found");
            }
           //将路径中所有的文件打印出来 filePaths.forEach(e-> System.out.println(e));
        }
    
        /**
         * 讲所有的.java结尾的 全限定名放到 beanNames
         */
        public void  initBeanNames(){
            for (String s : filePaths) {
                String replace = s.replace(basePath, "");
                if(replace.endsWith(".java")) {
                    replace = replace.substring(0, replace.length()-5);
                }
    
                char[] chars = replace.toCharArray();
                for (int i = 0; i < chars.length; i++) {
                    if(chars[i]=='\\'){
                        chars[i] = '.';
                    }
                }
                beanNames.add(basePackage+"."+new String(chars));
            }
            beanNames.forEach(System.out::println);
        }
    
        public void initBeans(){
            for (String beanName : beanNames) {
                try {
                    Class<?> aClass = Class.forName(beanName);
                    Annotation[] declaredAnnotations = aClass.getDeclaredAnnotations();
                    for (Annotation declaredAnnotation : declaredAnnotations) {
                        if(declaredAnnotation instanceof Component){
                            //反射:
                            Object o = aClass.newInstance();
                            beans.put(aClass.getName(),o);
                        }
                    }
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
                    e.printStackTrace();
                }
    
            }
    
            for (Map.Entry<String, Object> entry : beans.entrySet()) {
                Field[] declaredFields = entry.getValue().getClass().getDeclaredFields();
    
                for (Field field : declaredFields) {
    
                    Annotation[] declaredAnnotations = field.getDeclaredAnnotations();
    
                    for (Annotation annotation : declaredAnnotations) {
                        if(annotation instanceof Autowired){
                            //field 需要由我们来赋值
                            // 我们所持有的所有对象 在beans中
                            // 根据当前域中的类型的名字:反射
                            String name = field.getType().getName();
                            // 从beans 中获得对应的对象
                            Object o = beans.get(name);
                            field.setAccessible(true);
                            try {
                                field.set(entry.getValue(), o);
                            } catch (IllegalAccessException e) {
                                e.printStackTrace();
                            }
                        }
                    }
    
                }
    
    
            }
        }
        public Object getInstance(String beanName) {
            return beans.get(beanName);
        }
        private void initPath(){
            basePath="D:\\imitateIOC\\src\\main\\java\\com\\test\\springioc\\";
            basePackage="com.test.springioc";
        }
    
        public SpringIOC() {
            initPath();
            try {
                scan();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
            beanNames= new ArrayList<>();
            initBeanNames();
        }
    }

#### **Autowired和Component注解** ####

@Target(ElementType.FIELD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Autowired {
    }
    
    
    
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Component {
    }

#### SpringIOCTest 类 ####

public class SpringIOCTest {
    
        @Test
        public void testIOC() throws FileNotFoundException {
    
            //创建IOC容器
            SpringIOC springIOC = new SpringIOC();
            //初始化容器
            springIOC.initBeans();
            //从容器中获得TestController对象
            TestController instance = (TestController) springIOC.getInstance(TestController.class.getName());
            //调用其方法
            instance.test();
        }
    }

#### ![9bdcec1efb734c219fe825da6b8e254a.png][] ####

#### 总结： ####

整个环境可以归纳为两个阶段：

第一阶段：处理字符串，获得到类权限的名

第二阶段：根据类权限名创建对应的对象（**带有@Component的类才会创建对应的对象**），然后再遍历访问我们创建好的对象，判断所有的域是否带有@Autowired,如果有就从Bean中取出对应的对象设置进去。

通篇我们没有写new TestController，new UserService这种代码,都是由反射创建的对象设置进来，这就是这篇代码的基本逻辑。

源码已上传gitee平台:

[https://gitee.com/dont-live-in-the-past/copy-ioc.git][https_gitee.com_dont-live-in-the-past_copy-ioc.git]

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![db7d3000d4fd49a8bdb5751e52643dab.jpeg][]

[2f27ad00343b4454940d5753678bdaa0.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/3f79b818cfae4a44a645d0cf6a91d45f.png
[9bdcec1efb734c219fe825da6b8e254a.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/98296127d68845e2b78b748249962e54.png
[https_gitee.com_dont-live-in-the-past_copy-ioc.git]: https://gitee.com/dont-live-in-the-past/copy-ioc.git
[db7d3000d4fd49a8bdb5751e52643dab.jpeg]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/b3f753955639477faf6c9b64411cfad9.png