Spring中Bean的作用域和自动装配方式

这篇文章主要介绍了Spring中Bean的作用域和自动装配方式，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教

Bean的作用域

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

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 { @Test public 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 { @Test public 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; } @Override public 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

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