Spring---依赖注入问题

配置类中，手动new 对象

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@Configuration public class TestConfig {         @Bean     public TestInterface testInterface(){         System.out.println("init testInterface");         return buildTestInterfaceImpl();     }       @Bean("testInterfaceName")     public TestInterfaceName testInterfaceName(){         System.out.println("init testInterfaceName");         return new TestInterfaceNameImpl();     }       private TestInterface buildTestInterfaceImpl() {         TestInterfaceImpl testInterface = new TestInterfaceImpl();   -- 手动创建Bean         testInterface.init();         return testInterface;     }   }     public interface TestInterface {       void test();   }     public class TestInterfaceImpl implements TestInterface{       @Autowired     private TestInterfaceName testInterfaceName;     -- @Autowired注入依赖TestInterfaceName         @Override     public void test() {       }       public void init(){         System.out.println("init:"+ testInterfaceName);     } }     public interface TestInterfaceName {       void test(); }     public class TestInterfaceNameImpl implements TestInterfaceName{     @Override     public void test() {       } }     @Override     public void test() {       } }

　　

　　

　　

　　初始化结果：

　　　　init testInterfaceName
　　　　init testInterface
　　　　init:null

　　

　　由于手动new对象，不在spring的Bean容器管理，可能会导致手动new 对象的依赖注入失效；

 

解决

　　将手动new 对象的依赖使用构造器注入方式，使得手动创建的对象是完整的对象

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@Configuration public class TestConfig {       @Bean     public TestInterface testInterface(TestInterfaceName testInterfaceName){         System.out.println("init testInterface");         return buildTestInterfaceImpl(testInterfaceName);     }       @Bean("testInterfaceName")     public TestInterfaceName testInterfaceName(){         System.out.println("init testInterfaceName");         return new TestInterfaceNameImpl();     }       private TestInterface buildTestInterfaceImpl(TestInterfaceName testInterfaceName) {         TestInterfaceImpl testInterface = new TestInterfaceImpl(testInterfaceName);         testInterface.init();         return testInterface;     }   }     public interface TestInterface {       void test();   }     public class TestInterfaceImpl implements TestInterface{       private TestInterfaceName testInterfaceName;       public TestInterfaceImpl(TestInterfaceName testInterfaceName){  -- 构造器注入依赖         this.testInterfaceName = testInterfaceName;     }       @Override     public void test() {       }       public void init(){         System.out.println("init:"+ testInterfaceName);     } }     public interface TestInterfaceName {       void test(); }     public class TestInterfaceNameImpl implements TestInterfaceName{     @Override     public void test() {       } }     @Override     public void test() {       } }

　　

　　

 

循环依赖

　　由于循环依赖，会注入半成品对象，如果在启动时，有大量的初始化逻辑，可能会导致注入的依赖是未完成初始化的Bean；