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Spring框架第四篇之基于注解的DI注入
一、说明
与@Component注解功能相同,但意义不同的注解还有三个:
1)@Repository:注解在Dao实现类上
2)@Service:注解在Service实现类上
3)@Controller:注解在SpringMVC的处理器上
Bean作用域:
@Scope("prototype"):用于指定对象创建模式,可以是单例模式或者原型模式,默认是singleton
基本类型属性注入:
@Value
@Autowired:byType方式的注解式注入,即根据类型注解
@Qualifier("mySchool"):byName方式的注解式注入,在使用@Qualifier时必须与@Autowired联合使用
域属性注解:
@Resource:不加name属性则为byType方式的注解式注入,但前提是注入的对象只能有一个
@Resource(name="mySchool"):byName方式的注解式注入
Bean的生命始末:
@PostConstruct:当前Bean初始化刚完毕
@PreDestroy:当前Bean即将被销毁
@Configuration:表示当前类充当Spring容器,即所有的Bean将由这个类来创建
注意:
在举例之前声明几个问题:
1、注解需要依赖spring-aop-4.3.9.RELEASE.jar包,所以需要导入依赖包。
2、使用注解方式注入,配置文件需要添加约束头文件:
<?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">
也可以自己从Spring的说明文档中找到此头文件:
3、如果使用到了SpringJUnit4测试,则还需要导入spring-test-4.3.9.RELEASE.jar包
二、举例
1、首先创建一个School类:
package com.ietree.spring.basic.annotation.demo1; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; @Component("mySchool") public class School { @Value(value = "清华大学") private String name; public School() { super(); } public School(String name) { super(); this.name = name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "School [name=" + name + "]"; } }
创建Student类:
package com.ietree.spring.basic.annotation.demo1; import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; import javax.annotation.Resource; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; /** * 说明: * 与@Component注解功能相同,但意义不同的注解还有三个: * 1)@Repository:注解在Dao实现类上 * 2)@Service:注解在Service实现类上 * 3)@Controller:注解在SpringMVC的处理器上 * * Bean作用域: * @Scope("prototype"):用于指定对象创建模式,可以是单例模式或者原型模式,默认是singleton * * 基本类型属性注入: * @Value * * @Autowired:byType方式的注解式注入,即根据类型注解 * @Qualifier("mySchool"):byName方式的注解式注入,在使用@Qualifier时必须与@Autowired联合使用 * * 域属性注解: * @Resource:不加name属性则为byType方式的注解式注入,但前提是注入的对象只能有一个 * @Resource(name="mySchool"):byName方式的注解式注入 * * Bean的生命始末: * @PostConstruct:当前Bean初始化刚完毕 * @PreDestroy:当前Bean即将被销毁 */ //@Scope("prototype") @Component("myStudent") public class Student { @Value(value = "小明") private String name; @Value(value = "25") private int age; // @Autowired // @Qualifier("mySchool") // @Resource(name="mySchool") @Resource private School school;// 对象属性,也叫做域属性 public Student() { super(); } public Student(String name, int age) { super(); this.name = name; this.age = age; } public void setName(String name) { System.out.println("执行setName()"); this.name = name; } public void setAge(int age) { System.out.println("执行setAge()"); this.age = age; } public void setSchool(School school) { this.school = school; } @Override public String toString() { return "Student [name=" + name + ", age=" + age + ", school=" + school + "]"; } @PostConstruct public void initAfter(){ System.out.println("当前Bean初始化刚完毕"); } @PreDestroy public void preDestroy(){ System.out.println("当前Bean即将被销毁"); } }
创建MyJavaConfig类:
package com.ietree.spring.basic.annotation.demo1; import org.springframework.beans.factory.annotation.Autowire; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; /** * @Configuration:表示当前类充当Spring容器,即所有的Bean将由这个类来创建 */ @Configuration public class MyJavaConfig { @Bean(name="mySchool") public School mySchoolCreator(){ return new School("清华大学"); } // autowire=Autowire.BY_TYPE:指从当前类这个容器中查找与域属性的类型具有is-a关系的Bean // autowire=Autowire.BY_NAME:指从当前类这个容器中查找与域属性同名的Bean @Bean(name="myStudent", autowire=Autowire.BY_TYPE) public Student myStudentCreator(){ return new Student("小明", 25); } }
创建配置文件:
<?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"> <!-- 扫描 com.ietree.spring.basic.annotation.demo1这个包及其子包 --> <context:component-scan base-package="com.ietree.spring.basic.annotation.demo1"/> <!-- 扫描 com.ietree.spring.basic这个包的子包 --> <context:component-scan base-package="com.ietree.spring.basic.*"/> </beans>
创建测试类:
package com.ietree.spring.basic.annotation.demo1; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations="classpath:com/ietree/spring/basic/annotation/demo1/applicationContext.xml") public class MyTest { @Autowired private Student student; @Test public void test01() { String resource = "com/ietree/spring/basic/annotation/demo1/applicationContext.xml"; ApplicationContext ctx = new ClassPathXmlApplicationContext(resource); School school = (School) ctx.getBean("mySchool"); System.out.println(school); Student student = (Student) ctx.getBean("myStudent"); System.out.println(student); ((ClassPathXmlApplicationContext)ctx).close(); } public void test02(){ System.out.println(student); } }
Spring框架第四篇之基于注解的DI注入