Java Spring-注解进行属性注入

Posted 2020-10-13 hyserendipity

2017-11-06 21:19:43

一、Spring的注解装配Bean
Spring2.5 引入使用注解去定义Bean

• @Component 描述Spring框架中Bean

Spring的框架中提供了与@Component注解等效的三个注解

• @Repository 用于对DAO实现类进行标注(dao层)
• @Service 用于对Service实现类进行标注(service层)
• @Controller 用于对Controller实现类进行标注(web层)

//因为只有一个属性value，所以可以直接写。一般需要value="..."
@Component("user")
public class User {
    public void sayHello(){
        System.out.println("Hello World.");
    }
}

配置文件：

<?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 http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <!-- bean definitions here -->

    <context:component-scan base-package="spring5"/>


</beans>

 

二、注解进行属性注入

普通属性：@Value（value="..."）,这时候可以不写setter方法

对象属性：@Resource（name = "...."）

//因为只有一个属性value，所以可以直接写。一般需要value="..."
@Component("user")
public class User {
    @Value(value="Spring")
    private String s;

    public void sayHello(){
        System.out.println("Hello World.");
    }

    @Override
    public String toString() {
        return "User{" +
                "s=‘" + s + ‘\‘‘ +
                ‘}‘;
    }
}

 

三、XML和注解的混合使用

两种方式结合：一般使用XML注册Bean,使用注解进行属性的注入

首先介绍一些其他的注解配置：

(1)配置 Bean 初始化方法和销毁方法 :
* init-method  和 destroy-method.

• @PostConstruct  初始化
• @PreDestroy 销毁

@PostConstruct
public void setup(){
System.out.println("初始化...");
}
@PreDestroy
public void teardown(){
System.out.println("销毁...");
}

(2) 配置 Bean 的作用范围 :@Scope

@Component("user")
@Scope(value="prototype")
public class User {
    @Value(value="Spring")
    private String s;

    public void sayHello(){
        System.out.println("Hello World.");
    }

    @Override
    public String toString() {
        return "User{" +
                "s=‘" + s + ‘\‘‘ +
                ‘}‘;
    }
}

 (3)使用Java类来进行配置信息，在XML中扫描一下即可

@Configuration
public class BeanConfig {
    @Bean(name = "car")
    public Car showCar() {
        Car car = new Car();
        car.setName("长安");
        car.setPrice(40000d);
        return car;
    }

    @Bean(name = "product")
    public Product initProduct() {
        Product product = new Product();
        product.setName("空调");
        product.setPrice(3000d);
        return product;
    }
}

混合使用范例：

public class Person {
    @Autowired
    @Qualifier("car")
    private Car car;
    @Autowired
    @Qualifier(value = "plane")
    private Plane plane;

    @Override
    public String toString() {
        return "Person{" +
                "car=" + car +
                ", plane=" + plane +
                ‘}‘;
    }
}

配置文件：

<?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 http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <!-- bean definitions here -->

    <!--使属性注入注解生效-->
    <context:annotation-config/>

    <bean id="car" class="spring6.Car"/>
    <bean id="plane" class="spring6.Plane"/>

    <bean id="person" class="spring6.Person">
    </bean>

</beans>

 

四、集成Junit测试

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:spring-config.xml")
public class spring6 {

    @Autowired
    @Qualifier("person")
    private Person p;

    @Test
    public void demo(){
        System.out.println(p);
    }
}

配置文件：

<?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 http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <!-- bean definitions here -->

    <!--使属性注入注解生效-->
    <context:annotation-config/>

    <bean id="car" class="spring6.Car"/>
    <bean id="plane" class="spring6.Plane"/>

    <bean id="person" class="spring6.Person">
    </bean>

</beans>