ioc 過多的概念我再這裡就不解釋了 需要了解概念 點下邊連結  

概念理解了  手寫個ioc 就明白怎麼回事了  其實ioc沒有想象中的那麼難   註解+反射 就可以搞定 

這裡我是仿照spring設計的   的倆個註解 Autowired 和Component

專案結構圖

註解引入的類

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
 

 倆個註解

/**
 * 自動注入 註解
 * 
 */
@Target({ ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autowired {

}





/**
 * 指定需要容器管理的類
 * 
 */
@Target({ ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
public @interface Component {
	
}

先上倆個工具類吧    一個是掃描所有類的  一個是根據掃描的類注實力化物件的

import java.io.File;
import java.io.FileFilter;

public class ClassUtil {

	/**
	 * 獲取該路徑下所遇的class檔案和目錄
	 * 
	 * @param pkg
	 * @return
	 */
	public static File[] getClassFile(String filePath) {
		return new File(filePath).listFiles(new FileFilter() {
			@Override
			public boolean accept(File file) {
				return file.isFile() && file.getName().endsWith(".class") || file.isDirectory();
			}
		});
	}

}
 

import java.io.File;
import com.annotation.Component;
import com.ioc.IocContext;

public class AnnotationUtil {

    //獲取指定包路徑下實現 Component主鍵Bean的例項
    public static void addClassByAnnotation(String filePath, String packageName) {
        try {
            File[] files = ClassUtil.getClassFile(filePath);
            if (files != null) {
                for (File f : files) {
                    String fileName = f.getName();
                    if (f.isFile()) {
                        Class<?> clazz = Class.forName(packageName + "." + fileName.substring(0, fileName.lastIndexOf(".")));
                        //判斷該類是否實現了註解
                        if(clazz.isAnnotationPresent(Component.class)) {
                          IocContext.applicationContext.put(clazz, clazz.newInstance());
                        }
                    } else {
                        addClassByAnnotation(f.getPath(), packageName + "." + fileName);
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

重點來了  ，ioc 最重要的部分  iocContent 先掃描所有包  掃描到有註解的  放個 把物件 map集合裡  

import java.net.URL;
import java.util.Enumeration;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import com.util.AnnotationUtil;
/**
 * Ioc 容器實現類
 * 
 */
public class IocContext {
    public static final Map<Class<?>, Object> applicationContext = new ConcurrentHashMap<Class<?>, Object>();
    static{
    	// 指定需要掃描的包名
        String packageName = "com";
        try {
            initBean(packageName);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    private static void initBean(String packageName) throws Exception {
        Enumeration<URL> urls = Thread.currentThread().getContextClassLoader().getResources(packageName.replaceAll("\\.", "/"));
        while (urls.hasMoreElements()) {
           AnnotationUtil.addClassByAnnotation(urls.nextElement().getPath(), packageName);
        }
        //IOC實現， 自定注入
        IocUtil.inject();
    }
  
}

 底下是業務層

import java.lang.reflect.Field;
import java.util.Map;
import java.util.Map.Entry;
import com.annotation.Autowired;

/**
 * Ioc 注入實現
 * 
 */
public class IocUtil {
	public static void inject() {
		Map<Class<?>, Object> map = IocContext.applicationContext;
		try {
			for (Entry<Class<?>, Object> entry : map.entrySet()) {
				Class<?> clazz = entry.getKey();
				Object obj = entry.getValue();
				Field[] fields = clazz.getDeclaredFields();
				for (Field field : fields) {
					if (field.isAnnotationPresent(Autowired.class)) {
						Class<?> fieldClazz = field.getType();
						field.setAccessible(true);
						Object fieldObj = map.get(fieldClazz);
						field.set(obj, fieldObj);
					}
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

@Component
public class TestController {
    @Autowired
    public UserService userService;
    
    
    public void getUser() {
        User user = userService.getUser();
        System.out.println(user);
    }
}





public class User {
	private String userName;
	private Integer age;
	private Integer sex;

	public User(String userName, Integer age, Integer sex) {
		this.userName = userName;
		this.age = age;
		this.sex = sex;
	}

	public String getUserName() {
		return userName;
	}

	public void setUserName(String userName) {
		this.userName = userName;
	}

	public Integer getAge() {
		return age;
	}

	public void setAge(Integer age) {
		this.age = age;
	}

	public Integer getSex() {
		return sex;
	}

	public void setSex(Integer sex) {
		this.sex = sex;
	}

	@Override
	public String toString() {
		return "User [userName=" + userName + ", age=" + age + ", sex=" + sex + "]";
	}

}










@Component
public class UserService {
    public User getUser() {
        User user = new User("張三", 50, 22);
        return user;
    }
}

測試  

import com.demo.TestController;
import com.ioc.IocContext;

public class Main {
    public static void main(String[] args) throws Exception {
        TestController testController = (TestController)IocContext.applicationContext.get(TestController.class);
        testController.getUser();
    }
}

以上就是最簡單的ioc了

原始碼要的私聊，