Spring Bean初始化的几种常规方式

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• 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/beans https://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/beans https://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/beans https://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/beans https://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 { @Override public Object getObject() throws Exception { return RumenzA.createRumenzA(); } @Override public 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

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原文发布时间：2020-06-28
本文作者：入门小站
本文来自：“掘金”，了解相关信息可以关注“掘金”