spring bean 构造方法实例化

素颜马尾好姑娘i 2024-02-19 12:18 17阅读 0赞

spring框架实例化bean有3中方式，即构造方法实例化、静态工厂实例化、实例工厂实例化（其中，最常用的是构造方法实例化）

### 构造方法实例化 ###

spring容器可以调用bean对应类中的无参数构造方法来实例化bean，这种方式称为构造方法实例化

#### 1.创建web应用，并导入依赖的jar包 ####

![70][]

#### 2.创建beanClass类 ####

package instance;
    
    public class BeanClass {
    
    	public String message;
    
    	public BeanClass(String s) {
    		
    		this.message = s;
    	}
    
    	public BeanClass() {
    		this.message="构造方法实例化bean";
    	}
    	
    }

#### 3.创建配置文件 ####

<?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
            http://www.springframework.org/schema/beans/spring-beans.xsd">
    
        <bean id="constructorInstance" class="instance.BeanClass">
            
        </bean>
    
        
    
    </beans>

#### 4.创建测试类 ####

package test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import instance.BeanClass;
    
    public class TestInstance {
    	public static void main(String[] args) {
    		ApplicationContext appCon = new ClassPathXmlApplicationContext("applicationContext.xml");
    		
    		BeanClass b1 = (BeanClass)appCon.getBean("constructorInstance");
    		System.out.println(b1+b1.message);
    	}
    }

![70 1][]

[70]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/3eb7c6d35710400b880e9f5a8ae4b3c3.png
[70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/4e1a2fe28a5f499882c679566de5f4b2.png