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方式

目录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

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

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xmlns:p="http://springframework.org/schema/p"

xmlns:c="http://springframework.org/schema/c"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

<bean id = "user" class="indi.stitch.pojo.User" />

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xmlns:p="http://springframework.org/schema/p"

xmlns:c="http://springframework.org/schema/c"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

<bean id = "user" class="indi.stitch.pojo.User" />

scope = “singleton”

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xmlns:p="http://springframework.org/schema/p"

xmlns:c="http://springframework.org/schema/c"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xmlns:p="http://springframework.org/schema/p"

xmlns:c="http://springframework.org/schema/c"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

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);

SysXpDTgBsnstem.out.println(user == user2);

}

}

scope = “prototype”

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xmlns:p="http://springframework.org/schema/p"

xmlns:c="http://springframework.org/schema/c"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xmlns:p="http://springframework.org/schema/p"

xmlns:c="http://springframework.org/schema/c"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

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);

}

}

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

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

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");

PeoXpDTgBsnsple people = context.getBean("people", People.class);

people.getCat().shout();

people.getDog().shout();

}

}

输出结果

通过type自动装配

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://springframework.org/schema/beans http://springframework.org/schema/beans/spring-beans.xsd">

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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