4.9 Annotationbased container configuration

注解配置在XML配置之前执行，所以后者会覆盖前者。

　　　　　　　　　　　　　　　　　　　　　　-----Spring Docs

4.9.1 @Required

@Required应用于setter方法，例如：

public class SimpleMovieLister {

  private MovieFinder movieFinder;

  @Required
  public void setMovieFinder(MovieFinder movieFinder) {
      this.movieFinder = movieFinder;
  }

  // ...
}

@Required只是表明属性必须被设置，否则报异常NullPointerException。

4.9.2 @Autowired

通过 @Autowired的使用来消除 set ，get方法。

@Autowired 将分别寻找和它们类型匹配的 Bean，将它们作为 Method(Car car ,Office office) 的入参来创建 Bean。 

4.9.5 @Resource

public class SimpleMovieLister {

  private MovieFinder movieFinder;

  @Resource(name="myMovieFinder")
  public void setMovieFinder(MovieFinder movieFinder) {
      this.movieFinder = movieFinder;
  }
}

如果没有设置name，默认为the field name or setter method

public class SimpleMovieLister {

  private MovieFinder movieFinder;
//name "movieFinder" injected
  @Resource
  public void setMovieFinder(MovieFinder movieFinder) {
      this.movieFinder = movieFinder;
  }
}

public class MovieRecommender {
//looks for a bean named customerPreferenceDao
  @Resource
  private CustomerPreferenceDao customerPreferenceDao;
//
  @Resource
  private ApplicationContext context;

  public MovieRecommender() {
  }

  // ...
}

4.9.6 @PostConstruct and @PreDestroy

public class CachingMovieLister {

  @PostConstruct
  public void populateMovieCache() {
      // populates the movie cache upon initialization...
  }

  @PreDestroy
  public void clearMovieCache() {
      // clears the movie cache upon destruction...
  }
}

4.12 Java-based container configuration（基于java的Spring容器配置）

4.12.1 Basic concepts: @Configuration and @Bean

在别标记为@Configuration的类中配置容器。

the @Bean annotation plays the same role as the <bean/> element.