service类有两个构造函数,一个不带参,一个带参
public class BlockChainService { public BlockChainService() { System.out.println("不带参的构造器"); } public BlockChainService(int i) { System.out.println("带参的构造器"); } }
在config同时注入service类两个不同构造函数的bean
@Configuration public class BlockChainServiceConfig { @Bean BlockChainService blockChainService1(){ return new BlockChainService(); } @Bean BlockChainService blockChainService(){ return new BlockChainService(1); } }
当启动项目后BlockChainService类创建了 bean名为blockChainService和blockChainService1的两个bean(名称与BlockChainServiceConfig类使用@Bean注解的方法名一致),各种内存独立,相当于new了同一个类的 两个不同声明的对象。
那门在使用时如何区分不同bean呢?
第一种
@Autowired private BlockChainService blockChainService;
@Autowired private BlockChainService blockChainService1;
当一个类只有一个bean时,BlockChainService后的声明可以随便写,但是有两个以上的bean时,BlockChainService后的声明必须与bean名称一致,否则会报错,比方使用blockChainService2 就会出现如下错误:、
第二种@Autowired+@Qualifier
@Autowired @Qualifier("blockChainService") private BlockChainService blockChainService; @Autowired @Qualifier("blockChainService1") private BlockChainService blockChainService1;
@Qualifier里是正确的beanming ,这时BlockChainService 后声明可以随便写;
第三种@Resource注解
@Resource(name = "blockChainService") private BlockChainService blockChainService;
@Resource(name = "blockChainService1") private BlockChainService blockChainService1;
@Resource正确的beanming ,这时BlockChainService 后的声明可以随便写
第四种,通过bean名称到备案容器中直接找到对应的bean
BlockChainService blockChainService=(BlockChainService)SpringUtil.getBean("blockChainService"); BlockChainService blockChainService1=(BlockChainService)SpringUtil.getBean("blockChainService1");
SpringUtil类:
@Component public class SpringUtil implements ApplicationContextAware { private static ApplicationContext applicationContext = null; public SpringUtil() { } public void setApplicationContext(ApplicationContext arg0) throws BeansException { if (applicationContext == null) { applicationContext = arg0; } } public static ApplicationContext getApplicationContext() { return applicationContext; } public static void setAppCtx(ApplicationContext webAppCtx) { if (webAppCtx != null) { applicationContext = webAppCtx; } } /** * 拿到ApplicationContext对象实例后就可以手动获取Bean的注入实例对象 */ public static <T> T getBean(Class<T> clazz) { return getApplicationContext().getBean(clazz); } public static <T> T getBean(String name, Class<T> clazz) throws ClassNotFoundException { return getApplicationContext().getBean(name, clazz); } public static final Object getBean(String beanName) { return getApplicationContext().getBean(beanName); } public static final Object getBean(String beanName, String className) throws ClassNotFoundException { Class clz = Class.forName(className); return getApplicationContext().getBean(beanName, clz.getClass()); } public static boolean containsBean(String name) { return getApplicationContext().containsBean(name); } public static boolean isSingleton(String name) throws NoSuchBeanDefinitionException { return getApplicationContext().isSingleton(name); } public static Class<?> getType(String name) throws NoSuchBeanDefinitionException { return getApplicationContext().getType(name); } public static String[] getAliases(String name) throws NoSuchBeanDefinitionException { return getApplicationContext().getAliases(name); } }