3.装配Bean 基于XML

一、实例化方式

3种bean实例化方式：默认构造、静态工厂、实例工厂

1.默认构造

<bean id="" class="">  必须提供默认构造

2. 静态工厂

l 常用与spring整合其他框架（工具）

l 静态工厂：用于生成实例对象，所有的方法必须是static

<bean id=""  class="工厂全限定类名"  factory-method="静态方法">

UserService.java

package com.jd.inject.static_factory;

public interface UserService {

    public void addUser();

}

UserServiceImpl.java

package com.jd.inject.static_factory.impl;

import com.jd.inject.static_factory.UserService;

public class UserServiceImpl implements UserService {

    @Override
    public void addUser() {
        System.out.println("b_static_factory add user");
    }

}

MyBeanFactory.java

package com.jd.inject.static_factory;

import com.jd.inject.static_factory.impl.UserServiceImpl;

/**
 * @author weihu
 * @date 2018/8/12/012 18:54
 */
public class MyBeanFactory {

    /**
     * 创建实例
     * @return
     */
    public static UserService createService(){
        return new UserServiceImpl();
    }
}

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
                              http://www.springframework.org/schema/beans/spring-beans.xsd">

   <!--将静态工厂创建的实例交予spring
   class 确定静态工厂全限定类名
   factory-method 确定静态方法名,还是创建UserServiceImpl对象
   -->
    <bean id="userServiceId" class="com.jd.inject.static_factory.MyBeanFactory" factory-method="createService"></bean>
</beans>

测试类

TestStaticFactory.java

package com.jd.test;

import com.jd.inject.static_factory.MyBeanFactory;
import com.jd.inject.static_factory.UserService;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author weihu
 * @date 2018/8/12/012 18:57
 */
public class TestStaticFactory {

    @Test
    public void testStaticFactory(){
        //自定义工厂
        UserService userService = MyBeanFactory.createService();
        userService.addUser();

    }

    @Test
    public void testSpringStaticFactory(){
        //spring工厂
        String xmlPath="com/jd/inject/static_factory/beans.xml";
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
        UserService userServiceId = applicationContext.getBean("userServiceId", UserService.class);
        userServiceId.addUser();
    }
}

3. 实例工厂

实例工厂：必须先有工厂实例对象，通过实例对象创建对象。提供所有的方法都是“非静态”的。

UserService.java

package com.jd.inject.factory;

public interface UserService {

    public void addUser();

}

UserServiceImpl.java

package com.jd.inject.factory.impl;

import com.jd.inject.factory.UserService;

public class UserServiceImpl implements UserService {

    @Override
    public void addUser() {
        System.out.println("factory add user");
    }

}

MyBeanFactory.java

package com.jd.inject.factory;

import com.jd.inject.factory.impl.UserServiceImpl;

/**
 * @author weihu
 * @date 2018/8/12/012 18:54
 */
public class MyBeanFactory {

    /**
     * 创建实例
     * @return
     */
    public UserService createService(){
        return new UserServiceImpl();
    }
}

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
                              http://www.springframework.org/schema/beans/spring-beans.xsd">

 <!--创建工厂实例-->
 <bean id="myBeanFactoryId" class="com.jd.inject.factory.MyBeanFactory"></bean>
 <!--获得userservice
    factory-bean确定工厂实例
    factory-method 确定普通方法
 -->
 <bean id="userServiceId" factory-bean="myBeanFactoryId" factory-method="createService"></bean>
</beans>

测试类
TestFactory.java

package com.jd.test;

import com.jd.inject.factory.MyBeanFactory;
import com.jd.inject.factory.UserService;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author weihu
 * @date 2018/8/12/012 19:16
 */
public class TestFactory {

    @Test
    public void testFactory(){
        MyBeanFactory myBeanFactory=new MyBeanFactory();
        UserService userService = myBeanFactory.createService();
        userService.addUser();

    }

    @Test
    public void testSpringFactory(){
        String xmlPath="com/jd/inject/factory/beans.xml";
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
        UserService userServiceId = applicationContext.getBean("userServiceId", UserService.class);
        userServiceId.addUser();

    }
}