Spring容器解析与简单demo

git上项目路径: https://github.com/0ziyu0/handWriting

实现原理：本文采用2个全局的ConcurrentHashMap集合来实现beansAlias集合存放所有带自定义注解的类其中key:类名首字母小写,value:注解中value属性,没有则首字母小写。

                  containerBeans集合存放所有自定义注解的类来实现。

步骤: 1.扫描指定路径下的所有class文件。

         2.对其上有自定义注解的class放入一个全局的Map集合中,同时用一个容器来存放beanId(默认是类名首字母小写)[也可以更具类的类型来注入]。

         3.遍历所有Map集合对其class中属性上有自定义注解进行赋值(依赖注入)。

 

public class ClassPathApplicationContextCustomer {

    // 扫描包路径
    private String scanPackagePath = null;
    // 将所有自定义注解的class交给此类管理
    private ConcurrentHashMap<String, Object> containerBeans = new  ConcurrentHashMap<String, Object>();
    // 存放注解中bean的别名
    private ConcurrentHashMap<String, String> beansAlias = new ConcurrentHashMap<String, String>();
    
    public ClassPathApplicationContextCustomer(String scanPackagePath) {
        this.scanPackagePath = scanPackagePath;
        List<Class> annotationClassList = getAllAnnotationClass();
        initAnnotationBean(annotationClassList);
        for (Object classInfo : containerBeans.values()) { 
            attributeInjection(classInfo);
        }
        beansAlias = null;
    }
    
    // 得到包路径下所有的注解类
    private List<Class> getAllAnnotationClass() {

        List<Class> resultAllAnnotationClass = null;
        if(StringUtil.isNotEmpty(scanPackagePath)) {
            resultAllAnnotationClass = new ArrayList<Class>();
            String beanId = null;
            String className = null;
            // 获取包下所有类
            List<Class<?>> classeList = ClassUtil.getClasses(scanPackagePath);
            for (Class<?> classInfo : classeList) {
                CustomerService customerServiceAnnotation = classInfo.getDeclaredAnnotation(CustomerService.class);
                if(customerServiceAnnotation != null) {
                    resultAllAnnotationClass.add(classInfo);
                    // 是否有自定义bean的名字,没有则采用类名小写
                    beanId = customerServiceAnnotation.value();
                    // 防止类重名,最好不用SimpleName()方法,这里简单处理
                    className = classInfo.getSimpleName();
                    if(StringUtil.isEmpty(beanId)) {
                        beanId = StringUtil.toLowerCaseFirstOne(className);
                    }
                    beansAlias.put(className, beanId);
                }
            }
        }

        return resultAllAnnotationClass;
    }

    // 初始化bean容器[此方法也可以合并到getAllAnnotationClass()方法中]
    private void initAnnotationBean(List<Class> AnnotationClassList) {

        try {
            Object instance = null;
            String className = null;
            for (Class classInfo : AnnotationClassList) {
                instance = classInfo.newInstance();
                className = classInfo.getSimpleName();
                String beanId = beansAlias.get(className);
                containerBeans.put(beanId, instance);
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }

    }

    // 属性的依赖注入
    private void attributeInjection(Object object) {

        try {
            Class<? extends Object> classInfo = object.getClass();
            Field[] fieldArray = classInfo.getDeclaredFields();
            CustomerService customerServiceAnnotation = null;
            String filedName = null;
            Object injectionClass = null;
            for (Field field : fieldArray) {
                customerServiceAnnotation = field.getDeclaredAnnotation(CustomerService.class);
                if(customerServiceAnnotation != null) {
                    filedName = field.getName();
                    injectionClass = containerBeans.get(filedName);
                    if(injectionClass != null) {
                        field.setAccessible(true);
                        field.set(object, injectionClass);
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
    
    public Object getInstanceBean(String beanId) {
        
        Object resultObject = null;
        if(StringUtil.isNotEmpty(beanId)) {
            resultObject = containerBeans.get(beanId);
        }
        
        return resultObject;
        
    }
}

@Documented
@Target({ElementType.TYPE, ElementType.FIELD})
@Inherited
@Retention(RetentionPolicy.RUNTIME )
public @interface CustomerService {

    String value() default "";
//    String name() default "";
    
}

 测试代码

dao

package com.hand.customer.spring.dao;

public interface CustomerApplicationContextDao {

    public void testCustomerApplicationContextTest();
    
}

dao.impl

package com.hand.customer.spring.dao.impl;

import com.hand.customer.spring.annotation.CustomerService;
import com.hand.customer.spring.dao.CustomerApplicationContextDao;

@CustomerService("customerDao")
public class CustomerApplicationContextDaoImpl implements CustomerApplicationContextDao {

    public void testCustomerApplicationContextTest() {
        
        System.out.println("this is test customer application content test dao impl...");
        
    }

}

service

package com.hand.customer.spring.service;

public interface CustomerApplicationContextService {

    public void testCustomerApplicationContextTest();
    
}

service.impl

package com.hand.customer.spring.service.impl;

import com.hand.customer.spring.annotation.CustomerService;
import com.hand.customer.spring.dao.CustomerApplicationContextDao;
import com.hand.customer.spring.service.CustomerApplicationContextService;

@CustomerService()
public class CustomerApplicationContextServiceImpl implements CustomerApplicationContextService {
    
    @CustomerService("customerDao")
    private CustomerApplicationContextDao customerDao;
    
    public void testCustomerApplicationContextTest() {
        
        System.out.println("============== 注解版本(根据bean首字母小写注入) ==================");
        customerDao.testCustomerApplicationContextTest();
    }

}

Test方法

package com.hand.customer.spring;

import com.hand.customer.spring.service.CustomerApplicationContextService;

public class ClassPathApplicationContextCustomerTest {

    public static void main(String[] args) {
        
        ClassPathApplicationContextCustomer app = new ClassPathApplicationContextCustomer("com.hand.customer.spring");
        CustomerApplicationContextService customerService = (CustomerApplicationContextService) app.getInstanceBean("customerApplicationContextServiceImpl");
        customerService.testCustomerApplicationContextTest();
    }
    
}

运行测试