spring IOC——创建bean的三种方式_spring ioc 创建bean

创建bean的三种方式

1. 使用默认构造函数创建（默认构造函数创建bean对象，如果没有构造函数，则对象无法创建）

package com.ay.service;

public interface AccountService {
    public  void saveAccount();
}
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package com.ay.service.impl;

import com.ay.service.AccountService;

public class AccountServiceImpl implements AccountService {
    @Override
    public void saveAccount() {
        System.out.println("方法创建成功了");
    }

    public AccountServiceImpl() {
        System.out.println("对象开始创建了");
    }
}

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<?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="accountService" class="com.ay.service.impl.AccountServiceImpl"></bean>
</beans>
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package com.ay.ui;

import com.ay.service.AccountService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Client {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("bean.xml");
        AccountService as = (AccountService)ac.getBean("accountService");
        as.saveAccount();
    }
}
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package com.ay.service;

public interface AccountService {
    public  void saveAccount();
}
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2. 使用普通工厂中的方法创建对象（使用某个类中的方法创建对象，并存入spring容器）

<?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="InstanceFactory" class="com.ay.factory.InstanceFactory"></bean>
    <bean id="accountService" factory-bean="InstanceFactory" factory-method="getAccountService"></bean>
</beans>
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package com.ay.factory;

import com.ay.service.AccountService;
import com.ay.service.impl.AccountServiceImpl;

public class InstanceFactory {
    public AccountService getAccountService(){
        return new AccountServiceImpl();
    }
}
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package com.ay.service.impl;

import com.ay.service.AccountService;

public class AccountServiceImpl implements AccountService {
    @Override
    public void saveAccount() {
        System.out.println("方法创建成功了");
    }

    public AccountServiceImpl() {
        System.out.println("对象开始创建了");
    }
}
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3. 使用工厂中的静态方法创建对象（使用某个类中的静态方法创建对象，并存入spring容器）

package com.ay.factory;

import com.ay.service.AccountService;
import com.ay.service.impl.AccountServiceImpl;

public class StaticFactory {
    public static AccountService getAccountService(){
        return new AccountServiceImpl();
    }
}
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<?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="accountService" class="com.ay.factory.StaticFactory" factory-method="getAccountService"></bean>
</beans>
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运行截图