Spring Bean初始化的几种常规方式

通过构造方法实例化
通过静态工厂实例化
通过实例工厂实例化
通过FactoryBean实例化

RumenzA实体类

package com.rumenz;
public class RumenzA {private String id;private String name;public static RumenzA createRumenzA(){RumenzA rumenzA=new RumenzA();rumenzA.setId("123");rumenzA.setName("入门小站");return rumenzA;}public  RumenzA() {System.out.println("RumenzA 无参构造方法");}public RumenzA(String id) {this.id = id;System.out.println("ID构造方法");}// set get省略
}

构造方法

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttps://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="rumenz" class="com.rumenz.RumenzA" />
<bean id="rumenz1" class="com.rumenz.RumenzA"><constructor-arg name="id" value="1"/>
</bean>
</beans>

DemoApplication.java

package com.rumenz;import org.springframework.context.support.ClassPathXmlApplicationContext;
public class DemoApplication {public static  void main(String[] args) {ClassPathXmlApplicationContext  ca=new ClassPathXmlApplicationContext("beans.xml");RumenzA rumenzA=(RumenzA)ca.getBean("rumenz");}}

输出

xxx.DefaultListableBeanFactory - Creating shared instance of singleton bean 'rumenz'
RumenzA 无参构造方法
xxx.DefaultListableBeanFactory - Creating shared instance of singleton bean 'rumenz1'
ID构造方法

静态工厂

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttps://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="rFactory" class="com.rumenz.RumenzFactory" factory-method="rumenzFactory"/>
<bean id="rFactory1" class="com.rumenz.RumenzFactory" factory-method="rumenzFactory"><constructor-arg name="id" value="111"/>
</bean>
</beans>

RumenzFactory工厂类

package com.rumenz;
public class RumenzFactory {//静态方法public static RumenzA rumenzFactory(){return new RumenzA();}public static RumenzA rumenzFactory(String id){return new RumenzA(id);}}

DemoApplication.java

package com.rumenz;import org.springframework.context.support.ClassPathXmlApplicationContext;
public class DemoApplication {public static  void main(String[] args) {ClassPathXmlApplicationContext  ca=new ClassPathXmlApplicationContext("beans.xml");}}

输出

xxx.DefaultListableBeanFactory - Creating shared instance of singleton bean 'rFactory'
RumenzA 无参构造方法
xxx.DefaultListableBeanFactory - Creating shared instance of singleton bean 'rFactory1'
ID构造方法

实例工厂实例化

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttps://www.springframework.org/schema/beans/spring-beans.xsd"><bean  id="rFactory" class="com.rumenz.RumenzFactory" /><bean id="rumenz" factory-bean="rFactory" factory-method="rumenzFactory"></bean><bean id="rumenz1" factory-bean="rFactory" factory-method="rumenzFactory"><constructor-arg name="id" value="666"></constructor-arg></bean>
</beans>

RumenzFactory.java


package com.rumenz;
public class RumenzFactory {//不能用静态方法public  RumenzA rumenzFactory(){return new RumenzA();}public  RumenzA rumenzFactory(String id){return new RumenzA(id);}
}

DemoApplication.java

package com.rumenz;import org.springframework.context.support.ClassPathXmlApplicationContext;
public class DemoApplication {public static  void main(String[] args) {ClassPathXmlApplicationContext  ca=new ClassPathXmlApplicationContext("beans.xml");//RumenzA rumenzA=(RumenzA)ca.getBean("rFactory1");}}

输出

xxx.DefaultListableBeanFactory - Creating shared instance of singleton bean 'rumenz'
RumenzA 无参构造方法
xxx.DefaultListableBeanFactory - Creating shared instance of singleton bean 'rumenz1'
ID构造方法

通过FactoryBean实例化

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttps://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="rumenz-by-factoryBean"  class="com.rumenz.RumenzAFactoryBean"/>
</beans>

RumenzAFactoryBean.java

package com.rumenz;import org.springframework.beans.factory.FactoryBean;public class RumenzAFactoryBean implements FactoryBean {@Overridepublic Object getObject() throws Exception {return RumenzA.createRumenzA();}@Overridepublic Class<?> getObjectType() {return RumenzA.class;}
}

DemoApplication.java

package com.rumenz;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class DemoApplication {public static  void main(String[] args) {ClassPathXmlApplicationContext  ca=new ClassPathXmlApplicationContext("beans.xml");RumenzA rumenzA=(RumenzA)ca.getBean("rumenz-by-factoryBean");}}

输出/异步加载bean

xxx.DefaultListableBeanFactory - Creating shared instance of singleton bean 'rumenz-by-factoryBean'
RumenzA 无参构造方法

源码 : https://github.com/mifunc/Spring-Bean-common-instantiate

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Spring Bean初始化的几种常规方式

构造方法

静态工厂

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通过FactoryBean实例化

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