Spring利用依賴注入(DI)完成對IOC容器中各組件的依賴關係賦值
1. @Autowired:自動注入,主要由AutowiredAnnotationBeanPostProcessor 解析完成自動裝配功能
1)默認優先按照類型去容器中找對應的組件:applicationContext.getBean(BookDao.class);找到就賦值
2)如果找到多個相同類型的組件,再將屬性變量名稱作爲組件的id去容器中查找
applicationContext.getBean("bookDao")
3)@Qualifier("bookDao"):使用 @Qualifier 指定需要裝配的組件的id,而不是使用屬性名;
4)自動裝配默認一定要將屬性賦值好,否則會報錯,可使用 @Autowired(required=false) 屏蔽初始化錯誤,但獲取時依然會報錯;
5)@Primary:讓Spring進行自動裝配的時候,默認使用首選的bean,也可繼續使用@Qualifier指定需要裝配的bean的名字;
2. @Autowired : 可標註在構造器、參數、方法、屬性,都是從容器中獲取參數組件的值進行裝配
1)[標註在方法位置]:@Bean+方法參數;參數從容器中獲取;默認不寫@Autowired效果是一樣的;都能自動裝配
2)[標在構造器上]:如果組件只有一個有參構造器,這個有參構造器的@Autowired可以省略,參數位置的組件還是可以自動從容器中獲取
3)放在參數位置:
3. Spring 還支持使用 @Resource(JSR250) 和 @Inject(JSR330)【java規範的註解】
@Resource:
可以和@Autowired一樣實現自動裝配功能;默認是按照組件名稱進行裝配的;
沒有能支持@Primary功能沒有支持@Autowired(reqiured=false);
@Inject:
需要導入javax.inject的包,和Autowired的功能一樣。沒有required=false的功能;
@Autowired: 是Spring定義的; @Resource @Inject 都是java規範
4. 自定義組件想要使用Spring容器底層的一些組件(ApplicationContext,BeanFactory,xxx)
自定義組件實現xxxAware;在創建對象的時候,會調用接口規定的方法注入相關組件,重點 Aware 接口;
把Spring底層一些組件注入到自定義的Bean中;
xxxAware:功能使用xxxAwareProcessor 實現;
ApplicationContextAware ==> ApplicationContextAwareProcessor;
demo代碼如下:
@Configuration
@ComponentScan({"com.atguigu.service", "com.atguigu.dao", "com.atguigu.controller", "com.atguigu.bean"})
public class MainConifgOfAutowired {
@Primary
@Bean("bookDao2")
public BookDao bookDao() {
BookDao bookDao = new BookDao();
bookDao.setLable("2");
return bookDao;
}
/**
* @param car
* @return
* @Bean標註的方法創建對象的時候,方法參數的值從容器中獲取
*/
@Bean
// 一般此處 @Autowired 可省略
public Color color(@Autowired Car car) {
Color color = new Color();
color.setCar(car);
return color;
}
}
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.EmbeddedValueResolverAware;
import org.springframework.stereotype.Component;
import org.springframework.util.StringValueResolver;
@Component
public class Red implements ApplicationContextAware, BeanNameAware, EmbeddedValueResolverAware {
private ApplicationContext applicationContext;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
System.out.println("傳入的ioc:" + applicationContext);
this.applicationContext = applicationContext;
}
@Override
public void setBeanName(String name) {
System.out.println("當前bean的名字:" + name);
}
@Override
public void setEmbeddedValueResolver(StringValueResolver resolver) {
String resolveStringValue = resolver.resolveStringValue("你好 ${os.name} 我是 #{20*18}");
System.out.println("解析的字符串:" + resolveStringValue);
}
}
public class Color {
private Car car;
public Car getCar() {
return car;
}
public void setCar(Car car) {
this.car = car;
}
@Override
public String toString() {
return "Color [car=" + car + "]";
}
}
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
@Component
public class Car implements ApplicationContextAware, InitializingBean, DisposableBean {
private ApplicationContext applicationContext;
public Car() {
System.out.println("car constructor...");
}
public void init() {
System.out.println("car ... init...");
}
public void detory() {
System.out.println("car ... detory...");
}
@PostConstruct
public void postConstruct() {
System.out.println("car ... @PostConstruct...");
}
@PreDestroy
public void preDestroy() {
System.out.println("car ... @PreDestroy...");
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
@Override
public void destroy() throws Exception {
System.out.println("car ... destroy()...");
}
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("car ... afterPropertiesSet()...");
}
}
// 默認加在ioc容器中的組件,容器啓動會調用無參構造器創建對象,再進行初始化賦值等操作
@Component
public class Boss {
private Car car;
// 構造器要用的組件,都是從容器中獲取
public Boss(Car car) {
this.car = car;
System.out.println("Boss...有參構造器");
}
public Car getCar() {
return car;
}
// @Autowired
// 標註在方法,Spring容器創建當前對象,就會調用方法,完成賦值;
// 方法使用的參數,自定義類型的值從ioc容器中獲取
public void setCar(Car car) {
this.car = car;
}
@Override
public String toString() {
return "Boss [car=" + car + "]";
}
}
@Repository
public class BookDao {
private String lable = "1";
public String getLable() {
return lable;
}
public void setLable(String lable) {
this.lable = lable;
}
@Override
public String toString() {
return "BookDao [lable=" + lable + "]";
}
}
public class IOCTest_Autowired {
@Test
public void test01() {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConifgOfAutowired.class);
BookService bookService = applicationContext.getBean(BookService.class);
System.out.println(bookService);
//BookDao bean = applicationContext.getBean(BookDao.class);
//System.out.println(bean);
Boss boss = applicationContext.getBean(Boss.class);
System.out.println(boss);
Car car = applicationContext.getBean(Car.class);
System.out.println(car);
Color color = applicationContext.getBean(Color.class);
System.out.println(color);
System.out.println(applicationContext);
applicationContext.close();
}
}
5. Profile 根據環境註冊 bean,Spring爲我們提供的可以根據當前環境,動態的激活和切換一系列組件的功能
@Profile:指定組件在哪個環境的情況下才能被註冊到容器中,不指定,任何環境下都能註冊這個組件
1)加了環境標識的bean,只有這個環境被激活的時候才能註冊到容器中。默認是default環境
2)寫在配置類上,只有是指定的環境的時候,整個配置類裏面的所有配置才能開始生效
3)沒有標註環境標識的bean在,任何環境下都是加載的;
一般在 開發環境、測試環境、生產環境 分別有三個不同的數據源 dev、stg、prd,此時就能夠很好的使用這個功能
import javax.sql.DataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.EmbeddedValueResolverAware;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Profile;
import org.springframework.context.annotation.PropertySource;
import org.springframework.util.StringValueResolver;
import com.atguigu.bean.Yellow;
import com.mchange.v2.c3p0.ComboPooledDataSource;
@PropertySource("classpath:/dbconfig.properties")
@Configuration
public class MainConfigOfProfile implements EmbeddedValueResolverAware {
@Value("${db.user}")
private String user;
private StringValueResolver valueResolver;
private String driverClass;
@Bean
public Yellow yellow() {
return new Yellow();
}
@Profile("test")
@Bean("testDataSource")
public DataSource dataSourceTest(@Value("${db.password}") String pwd) throws Exception {
ComboPooledDataSource dataSource = new ComboPooledDataSource();
dataSource.setUser(user);
dataSource.setPassword(pwd);
dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/test");
dataSource.setDriverClass(driverClass);
return dataSource;
}
@Profile("dev")
@Bean("devDataSource")
public DataSource dataSourceDev(@Value("${db.password}") String pwd) throws Exception {
ComboPooledDataSource dataSource = new ComboPooledDataSource();
dataSource.setUser(user);
dataSource.setPassword(pwd);
dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/ssm_crud");
dataSource.setDriverClass(driverClass);
return dataSource;
}
@Profile("prod")
@Bean("prodDataSource")
public DataSource dataSourceProd(@Value("${db.password}") String pwd) throws Exception {
ComboPooledDataSource dataSource = new ComboPooledDataSource();
dataSource.setUser(user);
dataSource.setPassword(pwd);
dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/scw_0515");
dataSource.setDriverClass(driverClass);
return dataSource;
}
@Override
public void setEmbeddedValueResolver(StringValueResolver resolver) {
this.valueResolver = resolver;
driverClass = valueResolver.resolveStringValue("${db.driverClass}");
}
}
dbconfig.properties
db.user=root
db.password=123456
db.driverClass=com.mysql.jdbc.Driver
import javax.sql.DataSource;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import com.atguigu.bean.Boss;
import com.atguigu.bean.Car;
import com.atguigu.bean.Color;
import com.atguigu.bean.Red;
import com.atguigu.bean.Yellow;
import com.atguigu.config.MainConfigOfProfile;
import com.atguigu.config.MainConifgOfAutowired;
import com.atguigu.dao.BookDao;
import com.atguigu.service.BookService;
public class IOCTest_Profile {
//1、使用命令行動態參數: 在虛擬機參數位置加載 -Dspring.profiles.active=test
//2、代碼的方式激活某種環境,如下測試代碼實現
@Test
public void test01() {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
//1、創建一個applicationContext
//2、設置需要激活的環境
applicationContext.getEnvironment().setActiveProfiles("dev");
//3、註冊主配置類
applicationContext.register(MainConfigOfProfile.class);
//4、啓動刷新容器
applicationContext.refresh();
String[] namesForType = applicationContext.getBeanNamesForType(DataSource.class);
for (String string : namesForType) {
System.out.println(string);
}
Yellow bean = applicationContext.getBean(Yellow.class);
System.out.println(bean);
applicationContext.close();
}
}