1，基本概念
1）Gradle构建
compile 'org.springframework:spring-context:4.3.12.RELEASE'
2）在应用spring时，有两个地方可以声明一个bean。一个是在spring的xml配置文件中配置<bean>(或者@Configuration中定义bean方法)；一个是在代码中通过Component等标注声明。(Component、Repository、Service以及Controller)
3）BeanFactory接口，用于访问Spring的bean容器。The root interface for accessing a Spring bean container.image.png
singletonObjects用户缓存singleton bean
image.png
ApplicationContext是BeanFactory的子接口Central interface to provide configuration for an application.，它extends ListableBeanFactory。image.png
AnnotationConfigApplicationContext标准的应用上下文(@since 3.0)Standalone application context, accepting annotated classes as input，继承GenericApplicationContext(拥有属性DefaultListableBeanFactory)
DefaultListableBeanFactory它有一个beanDefinitionMap，来存放bean的定义。private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(256);
image.png
4）容器通过读取元配置，来初始化bean容器，然后指导对象的初始化、配置和组装。The container gets its instructions on what objects to instantiate, configure, and assemble by reading configuration metadata.
元配置可以通过xml、Java注解以及Java代码表示。configuration metadata is represented in XML, Java annotations, or Java code.
XML元配置：XML-based configuration metadata shows these beans configured as <bean/> elements inside a top-level <beans/> element.
Java-Based配置：Java configuration typically uses @Bean annotated methods within a @Configuration class.
2，主要注解和jar包。
1）spring-context包中的主要注解。
@Configuration通过@Configuration注解类，里面包含beans方法。declares bean methods, processed by the Spring container
@Bean注解在方法上， 可以产生一个由spring容器管理的bean对象。Indicates that a method produces a bean to be managed by the Spring container.
@Component注解类上，该类可以被spring自动检测，成为spring容器的bean。可以处理@Autowired等注解。when using annotation-based configuration and classpath scanning. this class can be auto-detection
@ComponentScan(value = "com.hzq.ioc")配置spring组件的扫描路径。Configures component scanning directives. default is this package
2）spring-context依赖引入几个spring jar包。
spring-core，spring的核心工具类，是其他组件的核心基础。eg: org.springframework.util.Assert断言类，org.springframework.util.StringUtils字符串工具类，org.springframework.util.DigestUtils处理MD5信息
spring-expression，spring的表达式语言。
spring-beans，含访问配置文件、创建和管理bean、以及进行IOC操作。如果应用只需基本的IoC/DI 支持，引入spring-core.jar 及spring-beans.jar 文件就可以了。
spring-aop，使用基于AOP 的Spring特性。如声明型事务管理（Declarative Transaction Management）需要aop的支持。
spring-context，为Spring 核心提供了大量扩展。提供ApplicationContext，从注解的类中获取bean的定义，并自动刷新spring的context。deriving bean definitions from the given annotated classes and automatically refreshing the context
3）面向接口编程。
@Bean注解bean方法和@Service / @Component等注解实现类。都可以将生成的bean对象，交给spring container管理。
正常情况，当一个bean交由spring container管理， 在其他地方注入该bean， 都是同一个对象。(单例，无状态的类。)
4）例子
@Bean//Indicates that a method produces a bean to be managed by the Spring container.
public MessageService messageService() {
return new MessageServiceImpl();
}
//@Service，This annotation serves as a specialization of @Component，
allowing for implementation classes to be autodetected through classpath scanning.
@Component // 或者@Service
public class MessageServiceImpl implements MessageService{
@Override
public void printMessage() {
System.out.println(this.getMessage());
}
@Override
public String getMessage() {
return "I am message";
}
}
package com.hzq.ioc.msg;
/**
* Created by hzq on 2017/10/14.
*/
public interface MessageService {
/**
* 打印msg的信息
*/
void printMessage();
/**
* 获取message信息
* @return
*/
String getMessage();
}
package com.hzq.ioc.msg;
/**
* Created by hzq on 2017/10/14.
*/
public class MessageServiceImpl implements MessageService{
@Override
public void printMessage() {
System.out.println(this.getMessage());
}
@Override
public String getMessage() {
return "I am message";
}
}
package com.hzq.ioc.msg;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
/**
* Created by hzq on 2017/10/14.
*/
@Component
public class InvokeMessage {
@Autowired//成员变量注入
private MessageService messageService;
private MessageService messageService2;
@Autowired//成员方法注入
public void injectionMessage(MessageService messageService){
System.out.println("这里注入 messageService2");
this.messageService2 = messageService;
}
public void testInjectionMessage(){
// 注入的是同一个对象
System.out.println("注入的两个对象相等吗?" + (messageService == messageService2));
this.messageService.printMessage();
messageService2.printMessage();
}
}
package com.hzq.ioc;
import com.hzq.ioc.msg.InvokeMessage;
import com.hzq.ioc.msg.MessageService;
import com.hzq.ioc.msg.MessageServiceImpl;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
/**
* Created by hzq on 2017/10/14.
*/
@Configuration//declares bean methods, processed by the Spring container
@ComponentScan(value = "com.hzq.ioc")//Configures component scanning directives. default this package
@Component//when using annotation-based configuration and classpath scanning. this class auto-detection
public class Application {
@Bean//Indicates that a method produces a bean to be managed by the Spring container.
public MessageService messageService() {
return new MessageServiceImpl();
}
public static void main(String[] args) {
// deriving bean definitions from the given annotated classes
// and automatically refreshing the context.
ApplicationContext context = new AnnotationConfigApplicationContext(Application.class);
//获取bean的两种方式
//1，<bean>xml配置、@Bean方法
//2，使用@Component等注解标识
MessageService messageService = context.getBean(MessageService.class);
messageService.printMessage();
InvokeMessage invokeMessage = context.getBean(InvokeMessage.class);//自动检测到，交由spring容器管理
invokeMessage.testInjectionMessage();
}
}
