JavaBean和SpringBean的区别及创建SpringBean方式

JavaBean和SpringBean的区别及创建SpringBean方式

目录一：对象，javaBean，SpringBean的区别1.什么是JavaBean2.什么是SpringBean3.SpringBean和JAVABean的区别二：如何定义一个SpringBean1.通过ClassPathXmlApplicationContext2.通过AnnotationConfigApplicationContext底层3.通过BeanDefinition4.通过FactoryBean5.通过Supplier

一：对象，JavaBean，SpringBean的区别

1.什么是JavaBean

javaBean要求所有属性为私有,该类必须有一个公共无参构造函数,private属性必须提供公共的Getter setter给外部访问

/**

* @author yzh

* @date 2021/4/29 8:42

**/

public class User {

//javaBean要求所有属性为私有,该类必须有一个公共无参构造函数,private属性必须提供公共的Getter setter给外部访问

private String name;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

2.什么是SpringBean

SpringBean是受Spring管理的对象,所有能受Spring管理的对象都可以是SpringBean

3.SpringBean和JAVABean的区别

用处不同：传统javabean更多地作为值传递参数，而spring中的bean用处几乎无处不在，任何组件都可以被称为bean

写法不同：传统javabean作为值对http://象，要求每个属性都提供getter和setter方法；但spring中的bean只需为接受设值注入的属性提供setter方法

生命周期不同：传统javabean作为值对象传递，不接受任何容器管理其生命周期；spring中的bean有spring管理其生命周期行为

二：如何定义一个SpringBean

准备工作:引入Spring依赖包

org.springframework

spring-context

5.2.14.RELEASE

1.通过ClassPathXmlApplicationContext

通过ClassPathXmlApplicationContext需要指定configLocation,所有我们现在resources目录下新建一个Spring.xml文件

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

xsi:schemaLocation="http://springframework.org/schema/beans

http://springframework.org/schema/beans/spring-beans-3.2.xsd">

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

xsi:schemaLocation="http://springframework.org/schema/beans

http://springframework.org/schema/beans/spring-beans-3.2.xsd">

同时相应对象重写toString方法,便于更好观察user1和user2

package org.example.bean;

/**

* @author yzh

* @date 2021/4/29 8:42

**/

public class User {

//javaBean要求所有属性为私有,该类必须有一个公共无参构造函数,private属性必须提供公共的Getter setter给外部访问

private String name;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public User(String name) {

this.name = name;

}

public User() {

}

@Override

public String toString() {

return "User{" +

"name='" + name + '\'' +

'}';

}

}

运行测试类

package org.example.bean;

import org.springframework.context.support.ClassPathXmlApplicationContext;

/**

* @author yzh

* @date 2021/4/29 8:45

**/

public class Main {

public static void main(String[] args) {

ClassPathXmlApplicationContext classPathXmlApplicationContext = new ClassPathXmlApplicationContext();

classPathXmlApplicationContext.setConfigLocation("Spring.xml");

classPathXmlApplicationContext.refresh();

User user1 = classPathXmlApplicationContext.getBean("user1",User.class);

System.out.println(user1);

User user2 = classPathXmlApplicationContext.getBean("user2", User.class);

System.out.println(user2);

}

}

运行结果如下

User{name='zhangsan'}

User{name='lisi'}

2.通过AnnotationConfigApplicationContext底层

也是通过BeanDefinition实现

*@Bean@Component@Service@Controller都可以;一般@Service用于Service层,@Controller用于Controller层,此处以@Bean为例

新建一个Config类,并给User打上@Bean标签

package org.example.bean;

import org.sprLOBMmingframework.context.annotation.Bean;

/**

* @author yzh

* @date 2021/4/29 9:20

**/

public class Config {

@Bean

public User user(){

return new User();

}

}

通过AnnotationConfigApplicationContext获取bean,并打印bean对象

package org.example.bean;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

/**

* @author yzh

* @date 2021/4/29 8:45

**/

public class Main {

public static void main(String[] args) {

AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext();

annotationConfigApplicationContext.register(Config.class);

annotationConfigApplicationContext.refresh();

User user = annotationConfigApplicationContext.getBean("user",User.class);

System.out.println(user);

}

}

运行结果

User{name='null'}

3.通过BeanDefinition

package org.example.bean;

import org.springframework.beans.factory.support.AbstractBeanDefinition;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

/**

* @author yzh

* @date 2021/4/29 8:45

**/

public class Main {

public static void main(String[] args) {

AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext();

AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition().getBeanDefinition();

//定义一个Bean

beanDefinition.setBeanClass(User.class);

//把生成的Bean注册到容器中

annotationConfigApplicationContext.refresh();

annotationConfigApplicationContext.registerBeanDefinition("userTest",beanDefinition);

User userTest = annotationConfigApplicationContext.getBean("userTest", User.class);

System.out.println(userTest);

}

}

运行结果

User{name='null'}

4.通过FactoryBean

4.1通过FactoryBean与注解方式

首先新建一个Person类

package org.example.bean;

import org.springframework.stereotype.Component;

/**

* @author yzh

* @date 2021/4/29 10:00

**/

public class Person {

}

然后新建一个PersonFactoryBean类,并实现FactoryBean接口,重写其方法,为其打上@component注解, 此处和在Person类上打注解是同一效果

package org.example.bean;

import org.springframework.beans.factory.FactoryBean;

import org.springframework.stereotype.Component;

/**

* @author yzh

* @date 2021/4/29 10:01

**/

@Component("person")

public class PersonFactoryBean implements FactoryBean {

@Override

public Object getObject() throws Exception {

return new Person();

}

@Override

public Class> getObjectType() {

return Person.class;

}

}

其次添加一个Config类打上@ComponentScan("org.example.bean"),目的是为了扫描包下的注解

package org.example.bean;

import org.springframework.context.annotation.ComponentScan;

/**

* @author yzh

* @date 2021/4/29 9:20

**/

@ComponentScan("org.example.bean")

public class Config {

}

最后通过AnnotationConfigApplicationContext获取Bean

package org.example.bean;

import org.springframework.beans.factory.support.AbstractBeanDefinition;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

/**

* @author yzh

* @date 2021/4/29 8:45

**/

public class Main {

public static void main(String[] args) {

//Config类为包扫描配置类

AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(Config.class);

Person person = annotationConfigApplicationContext.getBean("person", Person.class);

System.out.println(person);

}

}

运行结果

org.example.bean.Person@28ac3dc3

4.2通过Factory和BeanDefinition

1.同4.1一样新建一个Person类

2.同4.1一样新建一个PersonFactoryBean类,实现FactoryBean接口,但是不打注解

3.通过BeanDefinition获取对象

此处和注解生成的差别在于通过BeanDefinition注册的会生成两个Bean对象,一个是person对应的类型是Person,另一个是&person对应的类型是PersonFactoryBean,通过下面代码的getBean方法可以看出来!!

package org.example.bean;

import org.springframework.beans.factory.support.AbstractBeanDefinition;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

/**

* @author yzh

* @date 2021/4/29 8:45

**/

public class Main {

public static void main(String[] args) {

AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(Config.class);

AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition().getBeanDefinition();

////定义一个Bean

beanDefinition.setBeanClass(PersonFactoryBean.class);

//把生成的Bean注册到容器中

//annotationConfigApplicationContext.refresh();

//此处会生成2个Bean对象 第一个对象为&person对应的类型的PersonFactoryBean 第二个对象为person对应的类型为Person;

annotationConfigApplicationContext.registerBeanDefinition("person",beanDefinition);

PersonFactoryBean personFactoryBean = annotationConfigApplicationContext.getBean("&person", PersonFactoryBean.class);

System.out.println(personFactoryBean);

Person person = annotationConfigApplicationContext.getBean("person", Person.class);

System.out.println(person);

}

}

运行结果如下

org.example.bean.PersonFactoryBean@3aeaafa6

org.example.bean.Person@76a3e297

注

FactoryBean接口提供三个方法,但是我们重写了两个方法,这是因为另外一个方法是默认实现了的

FactoryBean接口方法如下:

package org.springframework.beans.factory;

import org.springframework.lang.Nullable;

public interface FactoryBean {

String OBJECT_TYPE_ATTRIBUTE = "factoryBeanObjectType";

@Nullable

T getObject() throws Exception;

@Nullable

Class> getObjectType();

//默认实现方法,是否是单例

default boolean isSingleton() {

return true;

}

}

5.通过Supplier

package org.example.bean;

import org.springframework.beans.factory.support.AbstractBeanDefinition;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.util.function.Supplier;

/**

* @author yzh

* @date 2021/4/29 8:45

**/

public class Main {

public static void main(String[] args) {

AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext();

annotationConfigApplicationContext.refresh();

annotationConfigApplicationContext.registerBean(User.class, new Supplier() {

@Override

public User get() {

User user = new User();

user.setName("123");

return user;

}

});

User user = annotationConfigApplicationContext.getBean("user", User.class);

System.out.println(user);

}

}

bean的注入方式本文只是提供了多种api，很多情况下底层其实用的都是一样的东西，只是提供了不同的使用方式，具体可以通过源码查看。

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