这篇文章主要介绍了Spring如何使用注解的方式创建bean,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
第一种使用配置类的方式
1、创建一个bean
package com.springbean;public class Person { private String name; private Integer age ; public Person(String name, Integer age) { this.name = name; this.age = age; } public void setName(String name) { this.name = name; } public void setAge(Integer age) { this.age = age; } public String getName() { return name; } public Integer getAge() { return age; } @Override public String toString() { return "Person{" + "name='" + name + '/'' + ", age=" + age + '}'; }}2、创建配置类：
import com.springbean.Person;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;@Configurationpublic class PersonConfig { @Bean //@Bean("myperson") 这是设置bean的名字 public Person person(){ System.out.println("已经创建实例");return new Person("张三",20); } }3、测试
import com.spring.config.PersonConfig;import com.springbean.Person;import org.springframework.context.ApplicationContext;import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class ApplicationTest { public static void main(String[] args) { ApplicationContext applicationContext = new AnnotationConfigApplicationContext(PersonConfig.class); Person bean = applicationContext.getBean(Person.class); System.out.println(bean); //获取bean的类型，默认是方法名，需要修改就在配置类中@Bean里面加上名字 String[] beanNamesForType = applicationContext.getBeanNamesForType(Person.class); for (String beanType : beanNamesForType){ System.out.println(beanType); } } }和xml配置文件一样，默认的bean是单例的，如果需要改变为prototype,xml配置文件里是加上scope="prototype",这里PersonConfig配置类中需要加上注解@Scope("prototype")。
介绍一下bean的几种类型的作用域。
不加注解测试：
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(PersonConfig.class); Person bean = applicationContext.getBean(Person.class); Person bean2 = applicationContext.getBean(Person.class); System.out.println(bean==bean2);//打印结果为true
加上注解@Scope("prototype")测试：
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(PersonConfig.class); Person bean = applicationContext.getBean(Person.class); Person bean2 = applicationContext.getBean(Person.class); System.out.println(bean==bean2);//打印结果为fale
我们也可以改变单例时ioc加载的时候就创建实例，只要在我们的PersonConfig配置类中加上@Lazy注解，使用懒加载。测试
public class ApplicationTest { public static void main(String[] args) { ApplicationContext applicationContext = new AnnotationConfigApplicationContext(PersonConfig.class); /* Person bean = applicationContext.getBean(Person.class); Person bean2 = applicationContext.getBean(Person.class); System.out.println(bean==bean2);*/ /* String[] beanNamesForType = applicationContext.getBeanNamesForType(Person.class); for (String beanType : beanNamesForType){ System.out.println(beanType); }*/ }}这是时打印栏将不会打印出“已经创建实例”，就实现的单例情况下的懒加载。
第二种使用@import注解的方式
新建一个student类
public class Student {}在配置类PersonConfig上使用@Import注解，这里面可以传入一个数组，用大括号{}
@Configuration@Import({Student.class})public class PersonConfig {测试：
public class DemoTest { ApplicationContext applicationContext = new AnnotationConfigApplicationContext(PersonConfig.class); @Test public void test(){ Student bean = applicationContext.getBean(Student.class); System.out.println(bean); }}打印结果：com.springbean.Student@2c34f934 ,注入成功
还可以在@Import中加入ImportSelector的实现类来实现bean的注入
创建Parent和Teacher类
public class Parent {}public class Teacher {}创建ImportSelector的实现类MyImportSelector,返回需要注入的bean,这里是全类名
public class myImportSelector implements ImportSelector{ @Override public String[] selectImports(AnnotationMetadata annotationMetadata) { return new String[]{"com.springbean.Parent","com.springbean.Teacher"}; }}修改PersonConfig，这里传入实现类MyImportSelector
@Configuration@Import({Student.class, myImportSelector.class})public class PersonConfig {测试：
Parent parent = applicationContext.getBean(Parent.class); Teacher teacher = applicationContext.getBean(Teacher.class); System.out.println(parent); System.out.println(teacher);
打印结果：
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。
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