一、Spring中的BeanFactory是什么?
BeanFactory是个基本的IoC容器,提供完整的IoC服务支持,负责对象创建的管理和依赖注入服务
如果没有特殊指定,默认采用延迟初始化策略(lazy-load)。只有当客户端对象需要访问容器中的某个受管对象的时候,才对该受管对象进行初始化以及依赖注入操作
public interface BeanFactory {
String FACTORY_BEAN_PREFIX = "&";
Object getBean(String var1) throws BeansException;
<T> T getBean(String var1, Class<T> var2) throws BeansException;
<T> T getBean(Class<T> var1) throws BeansException;
Object getBean(String var1, Object... var2) throws BeansException;
<T> T getBean(Class<T> var1, Object... var2) throws BeansException;
boolean containsBean(String var1);
boolean isSingleton(String var1) throws NoSuchBeanDefinitionException;
boolean isPrototype(String var1) throws NoSuchBeanDefinitionException;
boolean isTypeMatch(String var1, Class<?> var2) throws NoSuchBeanDefinitionException;
Class<?> getType(String var1) throws NoSuchBeanDefinitionException;
String[] getAliases(String var1);
}
二、BeanFactory的对象注册和依赖绑定的三种方式
1、直接编码方式(无需xml文件)
1.1 项目结构
1.2 各个代码
public class App {
private String says = "App";
private App(){
System.out.println("调用App无参构造");
}
public App(String says) {
System.out.println("调用App有参构造, 参数says为:" + says);
this.says = says;
}
public void say(){
System.out.println("App.say():" + says);
}
public String getSays() {
return says;
}
public void setSays(String says) {
this.says = says;
}
@Override
public String toString() {
return "App{" +
"says='" + says + '\'' +
'}';
}
}
public class Coder {
private App app;
private Coder(){
System.out.println("调用Coder无参构造");
}
public Coder(App app) {
System.out.println("调用Coder有参构造,参数app为:" + app.toString());
this.app = app;
}
public App getApp() {
return app;
}
public void setApp(App app) {
System.out.println("调用Coder.setApp(), 参数app为: " + app.toString());
this.app = app;
}
}
public class BeanFactoryTest extends TestCase {
/**
* 直接编码方式
*/
public void testRedirectCode() {
DefaultListableBeanFactory beanRegistry = new DefaultListableBeanFactory();
BeanFactory beanFactory = bindViaCode(beanRegistry);
Coder coder = (Coder) beanFactory.getBean("coder");
coder.getApp().say();
/**
* 输出为:
* //通过构造方法注入的情况
* 调用App无参构造
* 调用Coder有参构造,参数app为:App{says='App'}
* App.say():App
*
* //通过setter方式注入的情况下
* 调用Coder无参构造
* 调用App无参构造
* 调用Coder.setApp(), 参数app为: App{says='App'}
* App.say():App
*/
}
public static BeanFactory bindViaCode(BeanDefinitionRegistry registry){
AbstractBeanDefinition appBeanDefinition = new RootBeanDefinition(App.class);
AbstractBeanDefinition coderBeanDefinition = new RootBeanDefinition(Coder.class);
//将beanDefinition注册到容器中
registry.registerBeanDefinition("app", appBeanDefinition);
registry.registerBeanDefinition("coder", coderBeanDefinition);
//指定依赖关系
//1、可以通过构造方法注入
// ConstructorArgumentValues argumentValues = new ConstructorArgumentValues();
// argumentValues.addIndexedArgumentValue(0, appBeanDefinition);
// coderBeanDefinition.setConstructorArgumentValues(argumentValues);
//2、可以通过setter方法注入
MutablePropertyValues mutablePropertyValues = new MutablePropertyValues();
mutablePropertyValues.addPropertyValue("app", appBeanDefinition);
coderBeanDefinition.setPropertyValues(mutablePropertyValues);
//绑定完成
return (BeanFactory)registry;
}
}
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<!--这是 pom.xml文件 -->
<groupId>com.me.sourcecode</groupId>
<artifactId>spring-explore</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<spring.version>4.1.3.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${spring.version}</version>
</dependency>
</dependencies>
</project>
1.3 原理 (摘自《spring揭秘》)
打个比方说,BeanDefinitionRegistry就像图书馆的书架,所有的书是放在书架上的。虽然你
还书或者借书都是跟图书馆(也就是BeanFactory,或许BookFactory可能更好些)打交道,但书架才
是图书馆存放各类图书的地方。所以,书架相对于图书馆来说,就是它的“BookDefinitionRegistry”。
每一个受管的对象,在容器中都会有一个BeanDefinition的实例(instance)与之相对应,该
BeanDefinition的实例负责保存对象的所有必要信息,包括其对应的对象的class类型、是否是抽象
类、构造方法参数以及其他属性等。当客户端向BeanFactory请求相应对象的时候,BeanFactory会
通过这些信息为客户端返回一个完备可用的对象实例。RootBeanDefinition和ChildBean-
Definition是BeanDefinition的两个主要实现类。
2、xml配置文件方式
2.1 项目结构(上面的基础上)
2.2 新增文件SpringBean.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:context="http://www.springframework.org/schema/context"
xmlns:mybatis-spring="http://mybatis.org/schema/mybatis-spring"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jee="http://www.springframework.org/schema/jee"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
http://mybatis.org/schema/mybatis-spring http://mybatis.org/schema/mybatis-spring-1.2.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">
<bean id="app" class="com.me.sourcecode.bean.App"></bean>
<!--<bean id="coder" class="com.me.sourcecode.bean.Coder">-->
<!--<constructor-arg index="0">-->
<!--<ref bean="app" />-->
<!--</constructor-arg>-->
<!--</bean>-->
<bean id="coder" class="com.me.sourcecode.bean.Coder">
<property name="app" ref="app"></property>
</bean>
</beans>
BeanFactoryTest类里,增加对xml文件配置方式的测试
/**
* xml配置文件方式
*/
public void testXmlFile(){
DefaultListableBeanFactory beanRegistry = new DefaultListableBeanFactory();
BeanFactory beanFactory = bindViaXmlFile(beanRegistry);
Coder coder = (Coder) beanFactory.getBean("coder");
coder.getApp().say();
}
public static BeanFactory bindViaXmlFile(BeanDefinitionRegistry registry) {
XmlBeanDefinitionReader xmlBeanDefinitionReader = new XmlBeanDefinitionReader(registry);
xmlBeanDefinitionReader.loadBeanDefinitions("classpath*:SpringBean.xml");
return (BeanFactory) registry;
}
2.3 原理(摘自《spring揭秘》)
XmlBeanDefinitionReader负责读取Spring指定格式的XML配置文件并解析,之后将解析后的文件内
容映射到相应的BeanDefinition,并加载到相应的BeanDefinitionRegistry中(在这里是DefaultListableBeanFactory)
3、基于注解的方式
3.1 项目结构(不变)
3.2 有修改的内容
@Component
public class App {
private String says = "App";
private App(){
System.out.println("调用App无参构造");
}
public App(String says) {
System.out.println("调用App有参构造, 参数says为:" + says);
this.says = says;
}
public void say(){
System.out.println("App.say():" + says);
}
public String getSays() {
return says;
}
public void setSays(String says) {
this.says = says;
}
@Override
public String toString() {
return "App{" +
"says='" + says + '\'' +
'}';
}
}
@Component
public class Coder {
@Autowired
private App app;
private Coder(){
System.out.println("调用Coder无参构造");
}
public Coder(App app) {
System.out.println("调用Coder有参构造,参数app为:" + app.toString());
this.app = app;
}
public App getApp() {
return app;
}
public void setApp(App app) {
System.out.println("调用Coder.setApp(), 参数app为: " + app.toString());
this.app = app;
}
}
SpringBean.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"
xmlns:mybatis-spring="http://mybatis.org/schema/mybatis-spring"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jee="http://www.springframework.org/schema/jee"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
http://mybatis.org/schema/mybatis-spring http://mybatis.org/schema/mybatis-spring-1.2.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">
<context:component-scan base-package="com.me.sourcecode.bean" />
</beans>
BeanFactoryTest增加基于注解方式的测试
/**
* 基于注解的方式
*/
public void testAnnoation(){
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("SpringBean.xml");
Coder coder = (Coder) applicationContext.getBean("coder");
coder.getApp().say();
/**
* 输出为:
* 调用App无参构造
* 调用Coder无参构造
*
* App.say():App
*/
}
3.3 原理
可以看到输出结果中,没有调用Coder.setApp()这一句,而又有App.say(): App这一句。它是Coder里面的app是怎么注入进入的呢?
1) 通过SpringBean.xml文件的<context:component-scan base-package="com.me.sourcecode.bean" />,开始扫描这个路径,处理所有@Component注解标记的类(即App,Coder),生成对应的BeanDefinition
2)根据BeanDefinition创建Bean,此时Coder里面的app还是null,也就说还没有进行依赖注入
3)创建Bean之后,有个实例化Bean的流程。在这个流程中,AutowiredAnnotationBeanPostProcessor起了作用,通过反射的方式将App注入到Coder对象里面了。
反射 field.set(bean, value) ,此时bean是Coder的实例,value是App的实例