@Autowired 自動(dòng)裝載
@Autowired注解可以使用的地方很多表谊，比如常見(jiàn)的setter方法，constructors方法爽雄，普通方法等嗅回，一下逐一羅列并舉例說(shuō)明
1. Constructors 中使用
@Service
public class MovieService {
private static final Logger logger = LoggerFactory.getLogger(MovieService.class);
private final MovieRepository movieRepository;
// 構(gòu)造方法注入
@Autowired public MovieService(MovieRepository movieRepository) {
this.movieRepository = movieRepository;
}
public void printName() {
String name = this.movieRepository.getMovieName();
logger.info("Movie Name: {}",name);
}
}
從Spring4.3開(kāi)始如果類(lèi)僅有一個(gè)構(gòu)造函數(shù)，可以不使用
@Autowired來(lái)標(biāo)記構(gòu)造函數(shù)，但是如果類(lèi)中有幾個(gè)構(gòu)造函數(shù)哄褒，則至少需要有一個(gè)構(gòu)造函數(shù)被@Autowired標(biāo)記稀蟋，來(lái)告訴IoC容器使用那個(gè)構(gòu)造函數(shù)進(jìn)行初始化。
2. 傳統(tǒng)的setter方法中使用
@Service
public class MovieService {
private static final Logger logger = LoggerFactory.getLogger(MovieService.class);
private MovieRepository movieRepository;
public void printName() {
String name = this.movieRepository.getMovieName();
logger.info("Movie Name: {}",name);
}
// setter 方法注入
@Autowired public void setMovieRepository(MovieRepository movieRepository) {
this.movieRepository = movieRepository;
}
}
3. 任意方法上使用
@Service
public class MovieService {
private static final Logger logger = LoggerFactory.getLogger(MovieService.class);
private MovieRepository movieRepository;
private MovieCatalogRepository movieCatalog;
public void printName() {
String name = this.movieRepository.getMovieName();
String catalog = this.movieCatalog.getCatalog();
logger.info("Movie Name: {},Catalog: {}", new Object[] { name, catalog });
}
// 任意方法名稱(chēng)呐赡，和多個(gè)參數(shù)的注入
@Autowired public void prepare(MovieRepository movieRepository, MovieCatalogRepository movieCatalog) {
this.movieCatalog = movieCatalog;
this.movieRepository = movieRepository;
}
}
@Autowired除了在setter和constructors上之外還可以在任意方法名稱(chēng)中使用退客，將依據(jù)傳入?yún)?shù)進(jìn)行注入
4. 注入一組特定類(lèi)型的bean
public interface BasicRepository {
}
@Repository
public class MovieCatalogRepository implements BasicRepository{
public String getCatalog() {
return "Catalog..";
}
}
@Repository
public class MovieRepository implements BasicRepository{
public String getMovieName() {
return "King..";
}
}
@Service
public class MovieService {
private static final Logger logger = LoggerFactory.getLogger(MovieService.class);
// 以Set形式注入所有實(shí)現(xiàn)BasicRepository接口的bean
@Autowired private Set<BasicRepository> repositorySet;
// 以數(shù)組形式注入所有實(shí)現(xiàn)了BasicRepository接口的bean
@Autowired private BasicRepository[] repositoryArray;
// 以Map形式注入所有實(shí)現(xiàn)了BasicRepository接口的bean
@Autowired private Map<String, BasicRepository> repositoryMap;
// 注入spring上下文
@Autowired private ApplicationContext applicationContext;
public void printName() {
logger.info("打印Set中注入的bean...");
// 打印set中注入的bean
this.repositorySet.forEach(System.out::println);
logger.info("打印數(shù)組中注入的bean...");
// 打印數(shù)組中注入的bean
Arrays.stream(this.repositoryArray).forEach(System.out::println);
logger.info("打印Map中注入的bean...");
// 打印Map中注入的bean
this.repositoryMap.forEach((key, value) -> {
System.out.println(String.format("Key:%s,Value:%s", key, value));
});
logger.info("打印ApplicationContext中所有BasicRepository類(lèi)型的bean");
this.applicationContext.getBeansOfType(BasicRepository.class).forEach((key, value) -> {
System.out.println(String.format("Key:%s,Value:%s", key, value));
});
}
}
2018-12-06 10:09:53.800 INFO 15940 --- [ main] o.s.a.MovieService : 打印Set中注入的bean...
org.samples.annotations.MovieCatalogRepository@2d83c5a5
org.samples.annotations.MovieRepository@48d7ad8b
2018-12-06 10:09:53.801 INFO 15940 --- [ main] o.s.a.MovieService : 打印數(shù)組中注入的bean...
org.samples.annotations.MovieCatalogRepository@2d83c5a5
org.samples.annotations.MovieRepository@48d7ad8b
2018-12-06 10:09:53.801 INFO 15940 --- [ main] o.s.a.MovieService : 打印Map中注入的bean...
Key:movieCatalogRepository,Value:org.samples.annotations.MovieCatalogRepository@2d83c5a5
Key:movieRepository,Value:org.samples.annotations.MovieRepository@48d7ad8b
2018-12-06 10:09:53.802 INFO 15940 --- [ main] o.s.a.MovieService : 打印ApplicationContext中所有BasicRepository類(lèi)型的bean
Key:movieCatalogRepository,Value:org.samples.annotations.MovieCatalogRepository@2d83c5a5
Key:movieRepository,Value:org.samples.annotations.MovieRepository@48d7ad8b
當(dāng)以Key-Value形式注入一組特定類(lèi)型的bean時(shí)，key為bean的名稱(chēng)链嘀，value為bean的引用萌狂。
5. 結(jié)合@Primary、@Qualifier注入特定類(lèi)型的bean
如上例中所示怀泊，實(shí)現(xiàn)同一個(gè)接口的一組bean可以同時(shí)被注入茫藏，也可以被單個(gè)注入，在單個(gè)注入時(shí)可以結(jié)合@Primary或者@Qualifer注解使用霹琼。
- 使用
@Primary注解默認(rèn)注入beanPrimary用于指定多個(gè)相同類(lèi)型bean中务傲，在沒(méi)有指定候選bean的情況下默認(rèn)注入的bean
public interface BasicRepository {
}
@Repository
@Primary
public class MovieCatalogRepository implements BasicRepository{
public String getCatalog() {
return "Catalog..";
}
}
@Repository
public class MovieRepository implements BasicRepository{
public String getMovieName() {
return "King..";
}
}
@Service
public class MovieService {
private static final Logger logger = LoggerFactory.getLogger(MovieService.class);
/*
* 此處只指定了接口類(lèi)型，設(shè)置@Primary以后碧囊，將默認(rèn)注入@Primary標(biāo)記的bean
* 若多個(gè)實(shí)現(xiàn)類(lèi)中都沒(méi)有標(biāo)記@Primary則會(huì)拋出運(yùn)行時(shí)異常[UnsatisfiedDependencyException]
*/
@Autowired private BasicRepository repository;
public void printName() {
logger.info("打印默認(rèn)注入的bean");
logger.info("Bean Name:{},Bean HashCode:{}", this.repository.getClass().getName(),
this.repository.getClass().hashCode());
}
}
2018-12-06 11:14:09,960 INFO :-- [main .. ] o.s.a.MovieService 打印默認(rèn)注入的bean
2018-12-06 11:14:09,961 INFO :-- [main .. ] o.s.a.MovieService Bean Name:org.samples.annotations.MovieCatalogRepository,Bean HashCode:1852661033
上面
MovieCatalogRepository、MovieRepository都是實(shí)現(xiàn)了BasicRepository纤怒，在注入時(shí)如果采用接口注入的方式糯而，我們可以使用@Primary注解標(biāo)明在默認(rèn)情況下注入的bean，此例中為MovieCatalogRepository泊窘。
- 使用
@Qualifier來(lái)指出候選bean在接口注入中熄驼，若要注入指定的實(shí)現(xiàn)類(lèi)，可以使用@Qualifier來(lái)指出候選bean的名稱(chēng)
public interface BasicRepository {
}
@Repository
@Primary
public class MovieCatalogRepository implements BasicRepository{
public String getCatalog() {
return "Catalog..";
}
}
@Repository
public class MovieRepository implements BasicRepository{
public String getMovieName() {
return "King..";
}
}
@Service
public class MovieService {
private static final Logger logger = LoggerFactory.getLogger(MovieService.class);
/*
* 此處使用@Qualifier注解來(lái)標(biāo)記了默認(rèn)候選bean為movieRepository,則在Ioc容器注入時(shí)將
* 注入名稱(chēng)為movieRepository的bean
* 雖然MovieCatalogRepository類(lèi)標(biāo)記了@Primary烘豹，但是這只是在沒(méi)有指定候選bean時(shí)默認(rèn)的選擇
* 當(dāng)指定了候選Bean時(shí)瓜贾，會(huì)注入候選的Bean
*
*/
@Autowired @Qualifier("movieRepository") private BasicRepository repository;
public void printName() {
logger.info("打印默認(rèn)注入的bean");
logger.info("Bean Name:{},Bean HashCode:{}", this.repository.getClass().getName(),
this.repository.getClass().hashCode());
}
}
2018-12-06 11:25:21,385 INFO :-- [main .. ] o.s.a.MovieService 打印默認(rèn)注入的bean
2018-12-06 11:25:21,387 INFO :-- [main .. ] o.s.a.MovieService Bean Name:org.samples.annotations.MovieRepository,Bean HashCode:1027319653
6. 泛型注入
public interface Store<T> {
T get();
}
@Component
public class StringStore implements Store<String>{
@Override
public String get() {
return "String..";
}
}
@Component
public class IntegerStore implements Store<Integer>{
@Override
public Integer get() {
return 1;
}
}
@Component
public class StoreHandler {
private static final Logger logger= LoggerFactory.getLogger(StoreHandler.class);
@Autowired private Store<Integer> integerStore;
@Autowired private Store<String> stringStore;
public void test() {
logger.info("test bean type");
logger.info("IntegerStore get():{},StringStore get():{}",integerStore.get(),stringStore.get());
}
}
2018-12-06 13:29:05,424 INFO :-- [main .. ] o.s.a.StoreHandler test bean type
2018-12-06 13:29:05,424 INFO :-- [main .. ] o.s.a.StoreHandler IntegerStore get():1,StringStore get():String..
