Singleton and Prototype Bean Scope in Spring

Scope描述的是Spring容器如何新建Bean的实例的。

1> Singleton: 一个Spring容器只有一个Bean的实例，此为Spring的默认配置，全容器共享一个实例。

2> Prototype: 每次调用都新建一个Bean的实例。

3> Request: Web 项目中，给每一个 http request 新建一个Bean实例。

4> Session: Web项目中，给每一个 http session 新建一个Bean实例。

5> GlobalSession: 这个只在portal应用中有用，给每一个global http session 新建一个Bean实例。

But ....这里要说的是Singleton 和 Prototype的区别:

1.新建Spring Boot项目，有如下类：

2. POM 文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.study</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>demo</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.8.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

package com.sbia.ch2;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("com.sbia.ch2")
public class ConfigurationClass {

}

package com.sbia.ch2;

import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;

@Service
@Scope("prototype")
public class DemoPrototypeService {

}

package com.sbia.ch2;

import org.springframework.stereotype.Service;

@Service// 默认为 Singleton,相当于@Scope("singleton")
public class DemoSingletonService {

}

package com.sbia.ch2;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {

    public static void main(String[] args) {

        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
        context.register(ConfigurationClass.class);
        context.refresh();

        DemoSingletonService s1 = context.getBean(DemoSingletonService.class);
        DemoSingletonService s2 = context.getBean(DemoSingletonService.class);

        DemoPrototypeService p1 = context.getBean(DemoPrototypeService.class);
        DemoPrototypeService p2 = context.getBean(DemoPrototypeService.class);

        System.out.println("S1 与 S2是否相等： " + s1.equals(s2));
        System.out.println("P1 与P2是否相等： " + p1.equals(p2));

    }

}

Run Main.class as Java Application,get the result like below: