1、使用Java配置类装配Bean

对象之间的依赖关系，通过配置方法中的参数实现注入
两个注解：
（1）@Configuration
该注解标明这是个配置类，该类配置说明了如何在Spring应用的上下文中进行创建和装配Bean
（2）@Bean
该注解告诉Spring将这个方法返回的对象注册为Bean

2、创建dao、service、controller

• applicationContext文件代码：

    <bean id="TestController" class="com.neuedu.controller.TestController" autowire="byType">
        <!--<property name="testService" ref="TestService"></property>  -->
    </bean>
    
    <bean id="TestService" class="com.neuedu.service.TestService">
        <property name="testDao" ref="TestDao"></property>
    </bean>
    
    <bean id="TestDao" class="com.neuedu.dao.TestDao"></bean>

• TestController 代码：

public  class TestController {
    private TestService testService;

    public void setTestService(TestService testService) {
        this.testService = testService;
    }
    public void test() {
        testService.test();
    }
}

• TestService 代码：

public class TestService {
    private TestDao testDao;

    public void setTestDao(TestDao testDao) {
        this.testDao = testDao;
    }
    public void test() {
        System.out.println(testDao);
    }
}

• TestDao不写任何代码

3、创建一个配置类AppConfig

代码如下：

@Configuration
public class AppConfig{
  @Bean
  public TestDao getTestDao(){
    return new TestDao();
  }
  @Bean
  public TestService getTestService (TestDao testDao){
    TestService testService=new TestService ();
    testService.setTestDao(testDao);
    return testService;
  }
  @Bean
  public TestController getTestController  (TestService testService){
    TestController testController =new TestController ();
    testController .setTestService (testService);
    return testController ;
  }
}

• 测试代码

    @Test
    public void test() {
        ApplicationContext context = new AnnotationConfigApplicationContext(Appconfig.class);
        TestController testController = context.getBean(TestController.class);
        testController.test();
    }