Spring中Bean的作用域和自动装配方式 Spring中Bean的作用域和自动装配

Bean的作用域

默认配置
scope = “singleton”
scope = “prototype”

Bean的自动装配

通过name自动装配
通过type自动装配

Bean的作用域 Spring中bean的作用域共有singleton、prototype、request、session、application、websocket六种

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其中后四种都是用在Web应用程序中的，主要介绍前两种singleton(单例)和prototype(原型)
Bean的作用域范围为singleton时，所有实例共享一个对象。
Spring的默认配置为scope = “singleton”，以下两种配置的效果是一样的：

默认配置

scope = “singleton”

测试类及输出结果：

import indi.stitch.pojo.User; import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MyTest {@Testpublic void test2() {ApplicationContext context = new ClassPathXmlApplicationContext("namespace.xml"); User user = context.getBean("user", User.class); User user2 = context.getBean("user", User.class); System.out.println(user == user2); }}

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scope = “prototype”

测试类及输出结果：

import indi.stitch.pojo.User; import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MyTest {@Testpublic void test2() {ApplicationContext context = new ClassPathXmlApplicationContext("namespace.xml"); User user = context.getBean("user", User.class); User user2 = context.getBean("user", User.class); System.out.println(user == user2); }}

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Bean的自动装配 Spring中Bean的自动装配基于autowired标签实现
首先创建实体类People、Cat、Dog，People和Cat、Dog是组合关系，People中定义了依赖于Cat、Dog的属性
People实体类

package indi.stitch.pojo; public class People {private Cat cat; private Dog dog; public Cat getCat() {return cat; }public void setCat(Cat cat) {this.cat = cat; }public Dog getDog() {return dog; }public void setDog(Dog dog) {this.dog = dog; }@Overridepublic String toString() {return "People{" +"cat=" + cat +", dog=" + dog +'}'; }}

Cat实体类

package indi.stitch.pojo; public class Cat {public void shout() {System.out.println("miao~"); }}

Dog实体类

package indi.stitch.pojo; public class Dog {public void shout() {System.out.println("wang~"); }}

通过name自动装配

测试类及输出结果：

import indi.stitch.pojo.People; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MyTest {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml"); People people = context.getBean("people", People.class); people.getCat().shout(); people.getDog().shout(); }}

输出结果

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通过type自动装配

测试类和结果和上面相同

import indi.stitch.pojo.People; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MyTest {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml"); People people = context.getBean("people", People.class); people.getCat().shout(); people.getDog().shout(); }}

输出结果