不用Spring的Autowire且能看出依赖关系的写法)
背景：java游戏服务器，其实很多时候，都是不用SpringBoot这个东西，而是全程自己管理整个项目，这时想看清楚依赖关系，就可以采用下面的方式。
1)单例管理
package com.example.demo.util; import java.util.LinkedHashMap; import java.util.Map; public class SingletonManager { private static final Map<Class<?>, Object> singletons = new LinkedHashMap<>(); public static <T> T getIns(Class<T> clz) { Object single = singletons.get(clz); if (single == null) { try { single = init(clz); } catch (Exception e) { e.printStackTrace(); } } return (T) single; } public static Object init(Class<?> clz) throws Exception { if (singletons.get(clz) == null) { Object ins = clz.newInstance(); singletons.put(clz, ins); return ins; } return null; } }2)A
package com.example.demo.service; import com.example.demo.util.SingletonManager; public class AService { private BService bService; public static AService getInstance() { return SingletonManager.getIns(AService.class); } public void init() { bService = BService.getInstance(); } public void a() { System.out.println("a" + bService.b()); } public String aa(){ return "aa"; } } /* ab */3)B
package com.example.demo.service; import com.example.demo.util.SingletonManager; public class BService { private AService aService; public static BService getInstance() { return SingletonManager.getIns(BService.class); } public void init() { aService = AService.getInstance(); } public String b(){ return "b" + aService.aa(); } }4)Main
package com.example.demo; import com.example.demo.service.AService; import com.example.demo.service.BService; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); AService aService = AService.getInstance(); aService.init(); BService bService = BService.getInstance(); bService.init(); // 打印 aService.a(); } } /* abaa */
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