040_Spring注解开发
2024-10-12 05:22:11
Spring注解开发
<?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>
bean注册到Spring容器中
applicationContext.xml添加包扫描注解
<?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/>
<!--指定要扫描的包，包下的注解就会生效-->
<context:component-scan base-package="com.qing"/>
</beans>
实体类添加注解@Component
package com.qing.dao;
import org.springframework.stereotype.Component;
@Component
public class User {
private String name;
}
import com.qing.dao.User;
import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MyTest {
@Test
public void test01(){
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
User user = context.getBean("user", User.class);
System.out.println(user.getName());
}
}
User实体类被Spring管理，通过@Component注解注册到Spring容器中
属性注入
属性添加注解@Value("张三丰")
package com.qing.pojo;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class User {
@Value("张三丰")
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
import com.qing.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MyTest {
@Test
public void test01(){
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
User user = context.getBean("user", User.class);
System.out.println(user.getName());
}
}
@Component的衍生注解
在web开发中，会按照MVC三层架构分层，分别使用注解，但他们的作用和@Component注解是一样的，都是将类注册到spring容器中，只是为了标记分层使用不同的注解
dao层 @Repository
package com.qing.dao;
import org.springframework.stereotype.Repository;
@Repository
public class UserDao {
}
service层 @Service
package com.qing.service;
import org.springframework.stereotype.Service;
@Service
public class UserService {
}
controller层 @Controller
package com.qing.controller;
import org.springframework.stereotype.Controller;
@Controller
public class UserController {
}
自动装配
作用域
单例@Scope("singleton") 原型@Scope("prototype")
package com.qing.pojo;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
@Component
@Scope("singleton")
//@Scope("prototype")
public class User {
@Value("张三丰")
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
xml与注解区别
@Configuration 不使用Spring的xml配置，完全Java来做
JavaConfig是Spring的一个子项目，在Spring4之后，它成为了一个核心功能
添加配置类
@Configuration代表这是一个配置类
package com.qing.config;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
// @Configuration代表这是一个配置类，相当于applicationContext.xml
@Configuration
// @ComponentScan 扫描包下注解
@ComponentScan("com.qing.pojo")
// @Import 导入其他配置类
@Import(QingConfig2.class)
public class QingConfig {
}
实体类添加注解
package com.qing.pojo;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class User {
@Value("张三丰")
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
测试
import com.qing.config.QingConfig;
import com.qing.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class MyTest {
@Test
public void test01(){
// 通过AnnotationConfigApplicationContext获取容器，通过配置类的class加载
ApplicationContext context = new AnnotationConfigApplicationContext(QingConfig.class);
User user = context.getBean("user", User.class);
System.out.println(user.getName());
}
}
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