IOC容器，创建对象详细解析

  下面模仿一个具体的实例来说明问题，

1.bean.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"
xmlns:p="http://www.springframework.org/schema/p"
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">
<!-- 1. 默认无参数构造器
<bean id="user1" class="cn.itcast.b_create_obj.User"></bean>-->
<!-- 2. 带参数构造器 -->
<bean id="user2" class="cn.itcast.b_create_obj.User">
<constructor-arg index="0" type="int" value="100"></constructor-arg>
<constructor-arg index="1" type="java.lang.String" value="jack"></constructor-arg>
</bean>
<!-- 定义一个字符串，值是"Jack" ; String s = new String("jack")-->
<bean id="str" class="java.lang.String">
<constructor-arg value="jacks"></constructor-arg>
</bean>
<bean id="user3" class="cn.itcast.b_create_obj.User">
<constructor-arg index="0" type="int" value="100"></constructor-arg>
<constructor-arg index="1" type="java.lang.String" ref="str"></constructor-arg>
</bean>
<!-- 3. 工厂类创建对象 -->
<!-- # 3.1 工厂类，实例方法 -->
<!-- 先创建工厂 -->
<bean id="factory" class="cn.itcast.b_create_obj.ObjectFactory"></bean>
<!-- 在创建user对象，用factory方的实例方法 -->
<bean id="user4" factory-bean="factory" factory-method="getInstance"></bean>

<!-- # 3.2 工厂类： 静态方法 -->
<!--
class 指定的就是工厂类型
factory-method 一定是工厂里面的“静态方法”
-->
<bean id="user" class="cn.itcast.b_create_obj.ObjectFactory" factory-method="getStaticInstance"></bean>
<!-- 对象写法 -->
<!--
问题：spring配置文件中，bean节点的id与name属性的区别?
id 不能有特殊符号, 且唯一，且不能以数字开始
name 可以有特殊符号
-->
<bean id="test" name="1test" class="cn.itcast.b_create_obj.User"></bean>

</beans>


2.User
package cn.itcast.b_create_obj;

public class User {
private int id;
private String name;
public User() {
super();
System.out.println("------User对象创建【无参数构造器】------");
}

public User(int id, String name) {
System.out.println("-----User对象创建【带参数构造器】--------");
this.id = id;
this.name = name;
}

public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

@Override
public String toString() {
return "User [id=" + id + ", name=" + name + "]";
}
public void init_user() {
System.out.println("创建对象之后，初始化");
}
public void destroy_user() {
System.out.println("IOC容器销毁，user对象回收!");
}

}


3.ObjectFactory
package cn.itcast.b_create_obj;
//工厂，创建对象
public class ObjectFactory {
// 实例方法创建对象
public User getInstance(){
return new User(100,"工厂：调用实例方法");
}
// 静态方法创建对象
public static User getStaticInstance(){
return new User(200,"工厂：调用静态方法");
}

}


4.Junit测试
package cn.itcast.b_create_obj;

import org.junit.Test;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

public class App {

@Test
public void testIOC() throws Exception {
// 创建IOC容器对象
ApplicationContext ac = new ClassPathXmlApplicationContext("cn/itcast/b_create_obj/bean.xml");

// 从容器中获取bean
User user1 = (User) ac.getBean("user");

System.out.println(user1);

}

}