Spring Bean - xml 配置文件创建对象

类型：

1、值类型

2、null （标签）

3、特殊符号（< -> < ）

4、CDATA

<?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"><!--   引用外部bean--><bean id="school" class="com.gyk.ObjInject.School"><property name="location" value="henan"></property><property name="num" value="30000"></property></bean><bean id="school2" class="com.gyk.ObjInject.School"><property name="location" value="henan"></property><property name="num" value="30000"></property></bean><!--    <bean id="student" class="com.gyk.ObjInject.Student">--><!--        <property name="name" value="zs"></property>--><!--        <property name="age" value="22"></property>--><!--        <property name="school" ref="school"></property>--><!--    </bean>--><!--   嵌套内部bean--><bean id="student" class="com.gyk.ObjInject.Student"><property name="name" value="zs"></property><property name="age" value="22"></property><!--  对象属性--><property name="school"><bean class="com.gyk.ObjInject.School"><property name="location" value="henan"></property><property name="num" value="30000"></property></bean></property><!-- 设置数组属性--><property name="hobbies"><array><value>play</value><value>sing</value><value>ball</value></array></property><!-- 设置 list 属性--><property name="schoolList"><list><ref bean="school"></ref><ref bean="school2"></ref></list></property><!--        设置map 属性--><property name="stringSchoolMap"><list><map><entry><key><value>map1</value></key><ref bean="school"></ref></entry></map><map><entry><key><value>map2</value></key><ref bean="school2"></ref></entry></map></list></property></bean></beans>

package com.gyk.ObjInject;import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;import java.util.Arrays;
import java.util.List;
import java.util.Map;/*** ClassName: Student* Package: com.gyk.depInject* Description:** @Author Samuel* @Create 2024/7/24 09:20* @Version 1.0*/
public class Student {private String name;private int age;private School school;private String[] hobbies;private List<School> schoolList;private List<Map<String, School>> stringSchoolMap;public void setStringSchoolMap(List<Map<String, School>> stringSchoolMap) {this.stringSchoolMap = stringSchoolMap;}public void setSchoolList(List<School> schoolList) {this.schoolList = schoolList;}public void setName(String name) {this.name = name;}public void setHobbies(String[] hobbies) {this.hobbies = hobbies;}public void setAge(int age) {this.age = age;}public void setSchool(School school) {this.school = school;}@Overridepublic String toString() {return "Student{" +"name='" + name + '\'' +", age=" + age +", school=" + school +", hobbies=" + Arrays.toString(hobbies) +", schoolList=" + schoolList +", stringSchoolMap=" + stringSchoolMap +'}';}@Testpublic void getObj() {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("ObjInject.xml");System.out.println(applicationContext.getBean(Student.class));}public void setSchoolNum(int num) {this.school.setNum(num);}}

package com.gyk.ObjInject;/*** ClassName: School* Package: com.gyk.depInject* Description:** @Author Samuel* @Create 2024/7/24 09:21* @Version 1.0*/
public class School {private String location;private int num;public void setLocation(String location) {this.location = location;}public void setNum(int num) {this.num = num;}@Overridepublic String toString() {return "School{" +"location='" + location + '\'' +", num=" + num +'}';}
}2024-07-24 14:09:02 534 [main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@49872d67
2024-07-24 14:09:02 602 [main] DEBUG org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loaded 3 bean definitions from class path resource [ObjInject.xml]
2024-07-24 14:09:02 615 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'school'
2024-07-24 14:09:02 633 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'school2'
2024-07-24 14:09:02 633 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'student'
Student{name='zs', age=22, school=School{location='henan', num=30000}, hobbies=[play, sing, ball], schoolList=[School{location='henan', num=30000}, School{location='henan', num=30000}], stringSchoolMap=[{map1=School{location='henan', num=30000}}, {map2=School{location='henan', num=30000}}]}

util:list util:map

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:util="http://www.springframework.org/schema/util"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/utilhttp://www.springframework.org/schema/util/spring-util.xsd"><util:list id="list"><ref bean="school"></ref><ref bean="school2"></ref></util:list><util:list id="list2"><util:map id="map"><entry><key><value>school1</value></key><ref bean="school"></ref></entry><entry><key><value>school2</value></key><ref bean="school2"></ref></entry></util:map></util:list><property name="schoolList" ref="list"><!--            <list>--><!--                <ref bean="school"></ref>--><!--                <ref bean="school2"></ref>--><!--            </list>--></property>

p命名空间

    <!--   p命名空间  --><bean id="school3" class="com.gyk.ObjInject.School" p:num="11" p:location="ww"></bean><bean id="student2" class="com.gyk.ObjInject.Student" p:age="11" p:name="e11" p:hobbies="{1},{1}"p:schoolList-ref="list"p:stringSchoolMap-ref="list2"></bean>

bean 中读取本地 properties配置属性文件 druid 读取配置属性

先加依赖

 <!-- MySQL驱动 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.30</version></dependency><!-- 数据源 --><dependency><groupId>com.alibaba</groupId><artifactId>druid</artifactId><version>1.2.15</version></dependency>

注意配置 context 命名空间url 和 xsi location url。

 @Testpublic void getPropertiesInfo() throws SQLException {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("ObjInject.xml");DruidDataSource student = (DruidDataSource) applicationContext.getBean(DruidDataSource.class);System.out.println(student.getUrl());System.out.println(student.getUsername());System.out.println(student.getPassword());
//        System.out.println(student.getConnection());System.out.println(student.getCreatedTime());}jdbc:mysql://localhost:3306/testdb?serverTimezone=UTC
root
root
Thu Jul 25 11:20:26 CST 2024

bean的作用范围：单实例还是多实例（默认 singleon 单实例）

取值	含义	创建对象的时机
singleton（默认）	在IOC容器中，这个bean的对象始终为单实例	IOC容器初始化时
prototype	这个bean在IOC容器中有多个实例	获取bean时

Bean 生命周期

    /*** bean life cycle* 1. invoke null params controller* 2. set obj property* 3. before init* 4. invoke init method* 5. after init* 6. obj init success* 7. obj destroy* 8. ioc close*/

①具体的生命周期过程

bean对象创建（调用无参构造器）

给bean对象设置属性

bean的后置处理器（初始化之前）

bean对象初始化（需在配置bean时指定初始化方法）

bean的后置处理器（初始化之后）

bean对象就绪可以使用

bean对象销毁（需在配置bean时指定销毁方法）

IOC容器关闭

注意其中的initMethod()和destroyMethod()，可以通过配置bean指定为初始化和销毁的方法

<!-- 使用init-method属性指定初始化方法 -->
<!-- 使用destroy-method属性指定销毁方法 -->
<bean class="com.atguigu.spring6.bean.User" scope="prototype" 
init-method="initMethod" destroy-method="destroyMethod"><property name="id" value="1001"></property><property name="username" value="admin"></property><property name="password" value="123456"></property><property name="age" value="23"></property>
</bean>

⑤bean的后置处理器

bean的后置处理器会在生命周期的初始化前后添加额外的操作，需要实现BeanPostProcessor接口，且配置到IOC容器中，需要注意的是，bean后置处理器不是单独针对某一个bean生效，而是针对IOC容器中所有bean都会执行

public class MyBeanProcessor implements BeanPostProcessor {@Overridepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {System.out.println("☆☆☆" + beanName + " = " + bean);return bean;}@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {System.out.println("★★★" + beanName + " = " + bean);return bean;}
}

<!--        **⑤bean的后置处理器**-->
<!--        bean的后置处理器会在生命周期的初始化前后添加额外的操作，需要实现BeanPostProcessor接口，且配置到IOC容器中，需要注意的是，bean后置处理器不是单独针对某一个bean生效，而是针对IOC容器中所有bean都会执行-->

FactoryBean

FactoryBean是Spring提供的一种整合第三方框架的常用机制。和普通的bean不同，配置一个FactoryBean类型的bean，在获取bean的时候得到的并不是class属性中配置的这个类的对象，而是getObject()方法的返回值。通过这种机制，Spring可以帮我们把复杂组件创建的详细过程和繁琐细节都屏蔽起来，只把最简洁的使用界面展示给我们。

将来我们整合Mybatis时，Spring就是通过FactoryBean机制来帮我们创建SqlSessionFactory对象的。

class MyOBJ {}public class FactoryBean implements org.springframework.beans.factory.FactoryBean<MyOBJ> {@Overridepublic MyOBJ getObject() throws Exception {return new MyOBJ();}@Overridepublic Class<?> getObjectType() {return MyOBJ.class;}@Testpublic void re() {ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("FactoryBean.xml");MyOBJ factoryBean = (MyOBJ) context.getBean("factoryBean"); //只能传id ，FactoryBean.class 会报错System.out.println(factoryBean);//com.gyk.factory.MyOBJ@7df587ef}
}

基于xml自动装配

使用bean标签的autowire属性设置自动装配效果

自动装配方式：byType

byType：根据类型匹配IOC容器中的某个兼容类型的bean，为属性自动赋值

若在IOC中，没有任何一个兼容类型的bean能够为属性赋值，则该属性不装配，即值为默认值null

若在IOC中，有多个兼容类型的bean能够为属性赋值，则抛出异常NoUniqueBeanDefinitionException

  <bean id="controller" class="com.gyk.auto_wired.controller.controller" autowire="byType"></bean><bean id="service" class="com.gyk.auto_wired.service.service" autowire="byType"></bean><bean id="dao" class="com.gyk.auto_wired.dao.dao" autowire="byType"></bean>

public class controller {public void setServ(service serv) {this.serv = serv;}private service serv;public void run() {System.out.println("controller run ");serv.run();}@Testpublic void test() {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("autowire.xml");controller c = (controller) applicationContext.getBean(controller.class);c.run();}
}//
public class service {private dao d;public void setD(dao d) {this.d = d;}public void run() {System.out.println(" service run ");d.run();}
}
// public class dao {public void run() {System.out.println(" dao run ");}
}