Spring5:IOC注解
使用注解须知:
1:导入约束:导入context的命名空间
2:配置注解的支持:<context:annotation-config/>
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
https://www.springframework.org/schema/context/spring-context.xsd">
<!--注解支持-->
<context:annotation-config/>
</beans>
一:@Autowired
赋值:通过class类型自动会找容器中bean【利用反射机制,可以不用set】
项目改造:【场景】一个人拥有两只宠物
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
https://www.springframework.org/schema/context/spring-context.xsd">
<!--开启注解支持-->
<context:annotation-config/>
<!--注册Cat类-->
<bean class="com.spring.vo1.Cat"></bean>
<!--注册Dog类-->
<bean class="com.spring.vo1.Dog"></bean>
<!--注册People类-->
<bean id="people" class="com.spring.vo1.People" ></bean>
</beans>
People 注解注入Dog和Cat
package com.spring.vo1;
import org.springframework.beans.factory.annotation.Autowired;
public class People {
@Autowired/*通过class自动会找容器中bean */
private Dog dog;/*宠物狗*/
@Autowired/*通过class自动会找容器中bean */
private Cat cat;/*宠物猫*/
private String name;/*人的姓名*/
public Dog getDog() {
return dog;
}
public Cat getCat() {
return cat;
}
}
二:@Qualifier
配合@Autowired注解使用,如果容器中有两个同类型的bean,可以通过指定beanId进行注解
<!--开启注解支持-->
<context:annotation-config/>
<!--注册Cat类-->
<bean class="com.spring.vo1.Cat"></bean>
<!--注册Dog类01-->
<bean id="dog1" class="com.spring.vo1.Dog"></bean>
<!--注册Dog类02-->
<bean id="dog2" class="com.spring.vo1.Dog"></bean>
<!--注册People类-->
<bean id="people" class="com.spring.vo1.People" ></bean>
package com.spring.vo1;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
public class People {
@Autowired/*通过class自动会找容器中bean */
@Qualifier("dog1")/*通过beanId匹配*/
private Dog dog;
@Autowired/*通过class自动会找容器中bean */
private Cat cat;
private String name;/*人的姓名*/
public Dog getDog() {
return dog;
}
public Cat getCat() {
return cat;
}
}
三:@Resource
功能等同于@Autowired,比@Autowired更高级,JAVA提供的注解,既可以通过属性名--beanId(优先)查找,也可以通过对象类型查找;
另外:@Resource(name = "dog1") 等同于 @Autowired + @Qualifier
<!--开启注解支持-->
<context:annotation-config/>
<!--注册Cat类(对象类型)-->
<bean class="com.spring.vo1.Cat"></bean>
<!--注册Dog类(beanId)-->
<bean id="dog" class="com.spring.vo1.Dog"></bean>
<!--注册People类-->
<bean id="people" class="com.spring.vo1.People" ></bean>
package com.spring.vo1;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import javax.annotation.Resource;
public class People {
@Resource
private Dog dog;/*宠物狗*/
@Resource
private Cat cat;/*宠物猫*/
private String name;/*人的姓名*/
public Dog getDog() {
return dog;
}
public Cat getCat() {
return cat;
}
}
四:@Component
要先在spring配置文件中配置注解生效的扫描包:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
https://www.springframework.org/schema/context/spring-context.xsd">
<!--扫描包,这个包下面的注解就会生效-->
<context:component-scan base-package="com.spring" />
<!--开启注解支持-->
<context:annotation-config/>
</beans>
@@Component相当于实例化这个对象放到Spring容器中,相当于在spring配置文件中定义了一个bean;bean的id就是小写的类名
定义一个 UserInfo对象:
package com.spring.Vo;
import org.springframework.stereotype.Component;
@Component/*实例化这个对象*/
public class UserInfo {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
测试:
@Test
public void test01(){
//获取容器
ApplicationContext applicationContext =
new ClassPathXmlApplicationContext("applicationContext.xml");
//获取bean
UserInfo userInfo =applicationContext.getBean("userInfo", UserInfo.class);
userInfo.setName("zhangsan");
System.out.println(userInfo.getName());
}
四:@Value
给bean的属性做简单赋值,如果是复杂类型,还是建议用配置文件的方式
package com.spring.Vo;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component/*实例化这个对象*/
public class UserInfo {
@Value("king")/*给name赋值*/
private String name;
public String getName() {
return name;
}
}
测试:
@Test
public void test01(){
//获取容器
ApplicationContext applicationContext =
new ClassPathXmlApplicationContext("applicationContext.xml");
//获取bean
UserInfo userInfo =applicationContext.getBean("userInfo", UserInfo.class);
System.out.println(userInfo.getName());
}
五:@Repository
@Component的衍生注解,功能相同,一般会注解到Dao层。
六:@Service
@Component的衍生注解,功能相同,一般会注解到Service层。
七:@Controller
@Component的衍生注解,功能相同,一般会注解到Controller层。
八:@Scope
作用域注解:单例【singleton】、原型【prototype】
package com.spring.Vo;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
@Component/*实例化这个对象*/
@Scope("singleton")//作用域单例
public class UserInfo {
@Value("king")/*给name赋值*/
private String name;
public String getName() {
return name;
}
}