Spring三种方法实例化Bean_com.spring.pojo.cat;-优快云博客

本文详细介绍了Spring中通过类构造器、静态工厂和实例化工厂三种方式来实例化Bean的过程，包括创建构造方法、配置applicationContext.xml文件以及编写测试类的步骤。

第一种方法使用类构造器实例化Bean

1创建一个构造方法

package com.baidu.pojo;

public class UserService {

    public UserService() {

        System.out.println("----构造器方法----");
        //第一种方法使用类构造器实例化Bean
    }
}

2配置applicationContext.xml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"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <!--<bean id="userService" class="com.baidu.pojo.UserService">-->
</bean>
</beans>

3测试类

package com.baidu.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestUserService {
    public static void main(String[] args) {
 
   //从classpathx下载配置
    ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext
            ("applicationContext.xml");

   UserService bean=applicationContext.getBean(UserService.class);
   //第一种方法使用类构造器实例化Bean
  }
  }

2//第二种方法使用静态工厂实例化

1静态工厂方式实例化

package com.baidu.pojo;

public class UserServiceFactory {
public static  UserService createUserService(){

    return  new  UserService();//第二种方法使静态工厂器实例化Bean

}

}

2配置applicationContext.xml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"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

 
  
    <bean id="userService" class="com.baidu.pojo.UserServiceFactory" factory-method="createUserService">

    </bean>

3测试类

package com.baidu.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestUserService {
    public static void main(String[] args) {
  
  ApplicationContext applicationContext = new ClassPathXmlApplicationContext
            ("applicationContext.xml");
            
    System.out.println(applicationContext.getBean("userService"));
    //第二种方法使用静态工厂实例化Bean

  }
  }

第三种种方法使用实例化工厂实例化Bean

package com.baidu.pojo;

public class UserServiceInFactory {
    public  UserService createUserService(){

        return  new  UserService();
        //第三种方法实例化使静态工厂器实例化Bean

    }
}

2配置applicationContext.xml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"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">


    <bean id="userServiceInFactory" class="com.baidu.pojo.UserServiceInFactory" >
    </bean>
    <bean id="userService" factory-bean="userServiceInFactory" factory-
    method="createUserService">
    </bean>
    
 <!--第三种种方法使用实例化工厂实例化Bean-->
</beans>

3测试类

package com.baidu.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestUserService {
    public static void main(String[] args) {
    
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext
            ("applicationContext.xml");
    System.out.println(applicationContext.getBean("userService"));

  }
  }