仿写简单IOC

目录

TestController类:

UserService类:

 核心代码SpringIOC：

Autowired和Component注解

SpringIOCTest 类 

​编辑

总结：

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TestController类:

@Component
public class TestController {@Autowiredprivate 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 {@Testpublic 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();}
}

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

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