spring入门(二) 使用注解代替xml配置

1.导包(略)

2.applicationContext.xml如下:

<?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
        ">
    <!--注意配置xsd,要么报错:通配符的匹配很全面, 但无法找到元素 'context:component-scan' 的声明。-->

    <context:component-scan base-package="com.ice.bean"/>
</beans>

base-package扫描的包,会包含子包.

3.@Component

写法一: User类

import org.springframework.stereotype.Component;

@Component(value = "user") //等同于在xml里定义了 <bean id="user" class="" />
public class User {
    private String name;
    private Integer age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

main方法:

    ApplicationContext context = new ClassPathXmlApplicationContext("setting/applicationContext.xml");
    User user = (User) context.getBean("user");

写法二: User类

import org.springframework.stereotype.Component;

@Component
public class User {
    private String name;
    private Integer age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

main方法:

    ApplicationContext context = new ClassPathXmlApplicationContext("setting/applicationContext.xml");
    User user = context.getBean(User.class);

4.其他注解

@Repository
@Service
@Controller 这三个注解跟Component一个效果
@Scope(scopeName = "prototype")//singleton prototype
@Value 放在字段上,是反射实现赋值;放在set方法上,是通过调用方法赋值.

@Autowired 按照类型 //import org.springframework.beans.factory.annotation.Autowired;
@Qualifier 按照名称 //@Autowired @Qualifier 可以一起用
@Resource //import javax.annotation.Resource;

...