1.基本使用

1.基本介绍

2.快速入门

1.引入jar包

2.MyComponent.java

package com.sxs.spring.component;import org.springframework.stereotype.Component;/*** @Component 标识该类是一个组件，当不确定该类的层级的时候就使用这个注解* @author 孙显圣* @version 1.0*/@Component
public class MyComponent {
}

3.UserAction.java

package com.sxs.spring.component;import org.springframework.stereotype.Controller;/*** @Controller 用于标识该类是一个控制器（相当于servlet）* @author 孙显圣* @version 1.0*/
@Controller
public class UserAction {
}

3.UserDao.java

package com.sxs.spring.component;import org.springframework.stereotype.Repository;/*** @Repository 用来标识该类是一个dao* @author 孙显圣* @version 1.0*/
@Repository
public class UserDao {
}

4.UserService.java

package com.sxs.spring.component;import org.springframework.stereotype.Service;/*** @Service 用于标识该类是一个Service* @author 孙显圣* @version 1.0*/
@Service
public class UserService {
}

5.beans05.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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd"><!--component-scan 表示对指定包下的类进行扫描，并创建对象到容器base-package 指定要扫描的包--><context:component-scan base-package="com.sxs.spring.component"></context:component-scan>
</beans>

6.断点查看bean对象是否创建

7.测试

    //通过注解来配置bean@Testpublic void setBeanByAnnotation() {//从类路径下读取配置文件ApplicationContext ioc = new ClassPathXmlApplicationContext("beans05.xml");//分别获取这四个对象，由于是单例的所以可以直接通过类型获取MyComponent component = ioc.getBean(MyComponent.class);UserAction action = ioc.getBean(UserAction.class);UserDao userDao = ioc.getBean(UserDao.class);UserService userService = ioc.getBean(UserService.class);System.out.println("" + component + action + userDao + userService);}

3.注意事项和细节

2.自己实现spring注解

1.需求分析

2.思路分析图

3.编写自定义注解ComponentScan

package com.sxs.spring.annotation;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** 自定义注解：用于指定要扫描的包** @author 孙显圣* @version 1.0*/
@Target(ElementType.TYPE) //指定目前的注解可以修饰TYPE程序元素
@Retention(RetentionPolicy.RUNTIME) //指定注解的保留范围，在运行时可以生效
public @interface ComponentScan {String value() default ""; //指定注解可以传入一个String类型的值，用于指定要扫描的包
}

4.编写配置类SunSpringConfig

package com.sxs.spring.annotation;/*** @author 孙显圣* @version 1.0*/
@ComponentScan(value = "com.sxs.spring.component") //自定义注解：指定要扫描的包
public class SunSpringConfig {}

5.编写容器SunSpringApplicationContext

package com.sxs.spring.annotation;import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;
import org.springframework.util.StringUtils;import java.io.File;
import java.net.URL;
import java.util.concurrent.ConcurrentHashMap;/*** 类似于Spring原生的ioc容器** @author 孙显圣* @version 1.0*/
public class SunSpringApplicationContext {//传进来一个配置类的Class对象private Class configClass;//存放对象的容器private final ConcurrentHashMap<String, Object> ioc = new ConcurrentHashMap<>();//构造器，接收配置类的class对象public SunSpringApplicationContext(Class configClass) throws ClassNotFoundException, InstantiationException, IllegalAccessException {this.configClass = configClass;//获取要扫描的包//1.首先反射获取类的注解信息ComponentScan componentScan = (ComponentScan) this.configClass.getDeclaredAnnotation(ComponentScan.class);//2.通过注解来获取要扫描的包的路径String path = componentScan.value();//得到要扫描包的.class文件//1.获取类加载器ClassLoader classLoader = SunSpringApplicationContext.class.getClassLoader();//2.获取要扫描包的真实路径，默认刚开始在根目录下path = path.replace(".", "/");URL resource = classLoader.getResource(path);//3.由该路径创建一个文件对象，可使用resource.getFile()将URL类型转化为String类型File file = new File(resource.getFile());//4.遍历该文件夹下的所有.class文件if (file.isDirectory()) {File[] files = file.listFiles();for (File f : files ) {//反射注入容器//1.获取所有文件的全路径String absolutePath = f.getAbsolutePath();//只处理class文件if (absolutePath.endsWith(".class")) {//2.分割出类名String className = absolutePath.substring(absolutePath.lastIndexOf("\\") + 1, absolutePath.indexOf("."));//3.得到全路径String fullPath = path.replace("/", ".") + "." + className;//4.类加载器获取Class对象（也可以通过Class.forName，区别是后者会使类被静态初始化），判断是否有那四个注解Class<?> aClass = classLoader.loadClass(fullPath);if (aClass.isAnnotationPresent(Component.class) || aClass.isAnnotationPresent(Controller.class)|| aClass.isAnnotationPresent(Service.class) || aClass.isAnnotationPresent(Repository.class)) {//5.反射对象并放入到容器中Class<?> clazz = Class.forName(fullPath);Object o = clazz.newInstance();//默认是类名首字母小写作为keyioc.put(StringUtils.uncapitalize(className), o);}}}System.out.println("ok");}}//返回容器中的对象public Object getBean(String name) {return ioc.get(name);}}

6.测试

package com.sxs.spring.annotation;import org.junit.jupiter.api.Test;/*** @author 孙显圣* @version 1.0*/
public class test {@Testpublic void SunSpringApplicationContextTest() throws ClassNotFoundException, InstantiationException, IllegalAccessException {SunSpringApplicationContext ioc = new SunSpringApplicationContext(SunSpringConfig.class);Object myComponent = ioc.getBean("myComponent");Object userAction = ioc.getBean("userAction");Object userDao = ioc.getBean("userDao");Object userService = ioc.getBean("userService");System.out.println("" + myComponent + userService + userAction + userDao);}
}

3.自动装配

1.AutoWired方式

1.基本说明

2.UserDao.java

package com.sxs.spring.component;import org.springframework.stereotype.Repository;/*** @Repository 用来标识该类是一个dao* @author 孙显圣* @version 1.0*/
@Repository
public class UserDao {public void sayHi() {System.out.println("hi");}
}

3.UserService.java

package com.sxs.spring.component;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;/*** @Service 用于标识该类是一个Service* @author 孙显圣* @version 1.0*/
@Service
public class UserService {//自动装配//1.通过UserDao这个类型来匹配，如果有多个实例，则使用第二种方式匹配//2.通过userDao这个属性名字作为id匹配实例，如果还是匹配不到则报错@AutowiredUserDao userDao;public void sayHi() {userDao.sayHi();}
}

4.测试

    //测试@autowire自动装配@Testpublic void autowireTest() {//获取容器ApplicationContext ioc = new ClassPathXmlApplicationContext("beans05.xml");UserService bean = ioc.getBean("userService", UserService.class);bean.sayHi();}

2.Resource方式（推荐）

1.基本说明

2.UserDao.java

package com.sxs.spring.component;import org.springframework.stereotype.Repository;/*** @Repository 用来标识该类是一个dao* @author 孙显圣* @version 1.0*/
@Repository
public class UserDao {public void sayHi() {System.out.println("hi");}
}

3.UserService.java

package com.sxs.spring.component;import org.springframework.stereotype.Service;import javax.annotation.Resource;/*** @Service 用于标识该类是一个Service* @author 孙显圣* @version 1.0*/
@Service
public class UserService {//自动装配//1.通过name匹配：直接根据注解的属性name来进行匹配，如果匹配不到直接报错//2.通过类型匹配：必须保证是单例的，如果有多个实例，则直接报错//3.默认：先通过name属性匹配，如果匹配不上则按照类型匹配，都匹配不上才会报错@ResourceUserDao userDao;public void sayHi() {userDao.sayHi();}
}

4.泛型依赖注入

1.基本说明

1.基本介绍

2.参考关系图