Spring的扩展

￡神魔★判官ぃ 2021-09-11 03:14 332阅读 0赞

### 文章目录 ###

*   *  模拟SpringIoC的实现
     *   *  概念
         *  开发步骤
         *  Bean.java
         *  SpringContext.java
         *  Hello.java
         *  TestMyIoC.java
     *  模拟SpringDI的底层实现
     *   *  Student.java
         *  Teacher.java
         *  自定义注解
         *  TestMyDI.java
     *  Spring整合SpringMVC的项目实战
     *   *  需求
         *  项目结构
         *  创建RunApp.java
         *  创建application.yml文件
         *  创建Car类
         *  创建CarService接口
         *  创建CarServiceImpl实现类
         *  创建CarController类
         *  测试

## 模拟SpringIoC的实现 ##

### 概念 ###

SpringIoC控制反转底层实现利用了java自身提供的反射技术来创建对象

Class.forName(classPath).newInstance();

通过这种方式，spring控制了对象的生命周期，可以随时自行增强对象，如DI依赖注入，如AOP，环绕通知在类创建前后增强功能，如Transaction事务加强等。

### 开发步骤 ###

1.  创建容器管理bean,并初始化容器-> \[user,dept,hello\]
2.  创建spring容器,并初始化容器-> \{hello=new Hello(),user=new Uer() \}
3.  提供getBean(),根据bean的名字,从spring容器中获取对应的对象

### Bean.java ###

抽象Bean的定义，取代java中的Object，Spring框架中万物皆Bean。

package cn.tedu.design;
    //模拟spring管理bean,存放bean
    public class Bean { 
    	private String name;//bean名字-> hello
    	private String path;//bean对应的类路径->cn.tedu.desing.Hello
    	
    	public String getName() { 
    		return name;
    	}
    	public void setName(String name) { 
    		this.name = name;
    	}
    	public String getPath() { 
    		return path;
    	}
    	public void setPath(String path) { 
    		this.path = path;
    	}
    	
    }

### SpringContext.java ###

逻辑复杂，IoC实现的核心，最关键点还是怎么创建对象实例：

package cn.tedu.design;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    import java.util.concurrent.ConcurrentHashMap;
    //模拟spring框架,是spring的核心
    //1,创建容器管理bean-> [user,dept,hello]
    //2,创建spring容器-> {hello=new Hello(),user=new Uer() }
    //3,getBean(),有就直接取出来,没有就创建并放入容器
    public class SpringContext { 
    	//1,创建容器管理bean-> [user,dept,hello]
    	private List<Bean> beanFactory = new ArrayList<>();
    	//初始化容器
    	public SpringContext() throws Exception { 
    		//创建Bean,并加入容器中
    		Bean bean = new Bean();
    		bean.setName("hello");
    		bean.setPath("cn.tedu.pojo.Hello");
    		beanFactory.add(bean);
    		init();
    	}
    //2,创建spring容器-> {hello=new Hello(),user=new Uer() } //并发安全的map
    	private final Map<String, Object> factoryBeanObject = new ConcurrentHashMap<>();
    	//初始化spring容器-> {hello=new Hello(),user=new Uer() } 
    	public void init() throws Exception { 
    		//遍历beanFactory,得到每个bean
    		for(Bean b : beanFactory) { 
    			//map里的key
    			String key = b.getName();
    			//反射创建对象,作为value存入map
    			String path = b.getPath();
    			Object value = Class.forName(path).newInstance();
    			factoryBeanObject.put(key, value);
    		}
    	}
    	//3,getBean()有就直接取出来,没有就创建并放入容器
    	public Object getBean(String name) { 
    		return factoryBeanObject.get(name);//去map里根据key找value
    	}
    	
    }

### Hello.java ###

package spring;
    
    public class Hello { 
    	public void hi() { 
    		System.out.println("hi springioc");
    	}
    }

### TestMyIoC.java ###

package cn.tedu.spring;
    
    import cn.tedu.design.SpringContext;
    import cn.tedu.pojo.Hello;
    
    public class TestMyIOC { 
    	public static void main(String[] args) throws Exception { 
    		SpringContext spring = new SpringContext();
    		Hello o = (Hello)spring.getBean("hello");
    		System.out.println(o);//cn.tedu.pojo.Hello@6d06d69c
    		o.hi();
    	}
    }

## 模拟SpringDI的底层实现 ##

### Student.java ###

package cn.tedu.designdi;
    
    import org.springframework.stereotype.Component;
    
    @Component
    public class Student { 
        private String name="王一博";
    
        @MyAutowired //di
        private Teacher teacher;
    
        @Override
        public String toString() { 
            return "Student{" +
                    "name='" + name + '\'' +
                    ", teacher=" + teacher +
                    '}';
        }
    }

### Teacher.java ###

package cn.tedu.designdi;
    
    import org.springframework.stereotype.Component;
    
    @Component
    public class Teacher { 
        private String name="皮皮霞";
    
        @Override
        public String toString() { 
            return "Teacher{" +
                    "name='" + name + '\'' +
                    '}';
        }
    }

### 自定义注解 ###

package cn.tedu.designdi;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Target(ElementType.FIELD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface MyAutowired { 
        String value() default  "" ;
    }

### TestMyDI.java ###

package cn.tedu.designdi;
    import org.junit.Test;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import java.lang.reflect.Field;
    
    //有注解的属性就new
    public class TestDI { 
        @Test
        public void di() throws Exception{ 
            //获取Student类里的属性,哪个属性有MyAutowired注解就给他new一个
            Class s = Class.forName("cn.tedu.designdi.Student");
            Object o = s.newInstance();
            Field[] fs = s.getDeclaredFields();
            for (Field f : fs) { 
                MyAutowired an = f.getAnnotation(MyAutowired.class);
                if(an != null){ 
                    f.setAccessible(true);
                    f.set(o,new Teacher());
                }
            }
    // Student{name='王一博', teacher=Teacher{name='皮皮霞'}}
            System.out.println((Student)o);
        }
    }

## Spring整合SpringMVC的项目实战 ##

Spring用来管理项目中的所有Bean,需要使用注解@Component @Autowired @Service @Component等

Springmvc用来管理Controller层,需要使用的注解有@RestController @RequestMapping等

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### 需求 ###

访问链接： http://localhost:8080/car/get
    得到JSON数据： { "name":"保时捷","color":"红色","price":641000.0}

### 项目结构 ###

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### 创建RunApp.java ###

package cn.tedu;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    @SpringBootApplication
    public class RunApp { 
    	public static void main(String[] args) { 
    		SpringApplication.run(RunApp.class);
    	}
    }

### 创建application.yml文件 ###

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server:
      port: 8090

### 创建Car类 ###

package cn.tedu.pojo;
    
    import org.springframework.stereotype.Component;
    
    @Component
    public class Car { 
        private String name ;
        private String color;
        private double price;
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public String getColor() { 
            return color;
        }
    
        public void setColor(String color) { 
            this.color = color;
        }
    
        public double getPrice() { 
            return price;
        }
    
        public void setPrice(double price) { 
            this.price = price;
        }
    
        @Override
        public String toString() { 
            return "Car{" +
                    "name='" + name + '\'' +
                    ", color='" + color + '\'' +
                    ", price=" + price +
                    '}';
        }
    }

### 创建CarService接口 ###

package cn.tedu.service;
    
    import cn.tedu.pojo.Car;
    
    public interface CarService { 
        Car get();
    }

### 创建CarServiceImpl实现类 ###

package cn.tedu.service;
    
    import cn.tedu.pojo.Car;
    import org.springframework.stereotype.Service;
    
    @Service
    public class CarServiceImpl implements CarService{ 
        @Override
        public Car get() { 
            Car c = new Car();
            c.setName("保时捷");
            c.setColor("红色");
            c.setPrice(641000.0);
            return c;
        }
    }

### 创建CarController类 ###

package cn.tedu.controller;
    
    import cn.tedu.pojo.Car;
    import cn.tedu.service.CarService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    @RequestMapping("/car/")
    public class CarController { 
        @Autowired
        private CarService carService;
    
        @RequestMapping("get")
        public Car get(){ 
            return carService.get();
        }
    }

### 测试 ###

打开浏览器访问：http://localhost:8090/car/get

[img-cPl5tW93-1623125484759_RackMultipart20210608-4-9jbi5w_html_a71a298b5faabd1f.png]: /images/20210911/8f0bccebf6dd47e7968592ad5294a305.png
[img-lwPTMiRw-1623125484761_RackMultipart20210608-4-9jbi5w_html_dce2bb2f55ba2790.png]: /images/20210911/2941fb838ef84f77a3d8b76bf6e288d0.png
[img-UKL93CQl-1623125484763_RackMultipart20210608-4-9jbi5w_html_385e249cd30a3b66.png]: /images/20210911/693633a5f48549c3822d2f6af350500e.png
[_img-4ewwdgKa-1623125484764_RackMultipart20210608-4-9jbi5w_html_29b37e342a91ddee.png]: /images/20210911/8fb4c8f2b273496ba6606242ab6b6e73.png