• Spring-依赖注入对象


    代码结构:

    接上篇。

    package com.java.spring;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.METHOD,ElementType.FIELD})
    public @interface CustomizeAutowired {
        boolean required() default true;
    }
    package com.java.service;
    
    import com.java.spring.CustomizeComponent;
    
    @CustomizeComponent("orderService")
    public class OrderService {
    }
    package com.java.service;
    
    import com.java.spring.CustomizeAutowired;
    import com.java.spring.CustomizeComponent;
    import com.java.spring.CustomizeScope;
    
    @CustomizeComponent("userService")
    @CustomizeScope("prototype")
    public class UserService {
    
        @CustomizeAutowired
        public OrderService orderService;
    
        public void doSomething(){
            System.out.println(orderService);
        }
    }
    package com.java.spring;
    
    import java.io.File;
    import java.lang.reflect.Field;
    import java.lang.reflect.InvocationTargetException;
    import java.net.URL;
    import java.util.Map;
    import java.util.concurrent.ConcurrentHashMap;
    
    /**
     * 定制的Spring
     *  CustomizeComponentScan -->扫描路径-->获取Component注解-->CustomizeBeanDefinition-->放入beanDefinitionMap
     *
     */
    public class CustomizeApplicationContext {
        private Class customizeConfig;
    
        /**
         * 单例池
         */
        private ConcurrentHashMap<String,Object> singleTonMap = new ConcurrentHashMap<>();
    
        /**
         * bean定义Map
         */
        private ConcurrentHashMap<String,CustomizeBeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>();
    
        public CustomizeApplicationContext(Class customizeConfig) {
            this.customizeConfig = customizeConfig;
            scan();
            initAllSingleBean();
        }
    
    
        /**
         * CustomizeComponentScan -->扫描路径-->获取Component注解-->CustomizeBeanDefinition-->放入beanDefinitionMap
         */
        private void scan(){
            //获取传入配置类注解
            CustomizeComponentScan ccscan =
                    (CustomizeComponentScan) this.customizeConfig.getDeclaredAnnotation(CustomizeComponentScan.class);
    
            //获取扫描路径
            String scanPath = ccscan.value();
            //将路径转换成 com.xx->com/xx
            String dotScanPath = scanPath.replace(".", "//");
    
            //找到扫描路径下所有文件
            //注意:这里不能用 CustomizeApplicationContext.class.getResource("com/java/service")
            //原因是我们需要获取的是工程所在的路径
            ClassLoader classLoader = CustomizeApplicationContext.class.getClassLoader();
            URL resource = classLoader.getResource(dotScanPath);
            File file = new File(resource.getFile());
            if (file.isDirectory()) {
                File[] files = file.listFiles();
                for (File f : files) {
                    String fileName = f.getName();
                    if (fileName.endsWith(".class")) {
                        try {
                            //获取扫描路径下的class
                            Class<?> aClass = classLoader.loadClass(subFilePath(f.getPath()));
    
                            if(aClass.isAnnotationPresent(CustomizeComponent.class)){
                                //如果是自定义的注解,做自己想做的
                                CustomizeComponent ccp = aClass.getDeclaredAnnotation(CustomizeComponent.class);
                                String beanName =  ccp.value();
    
                                //判断是否是单例
                                CustomizeBeanDefinition beanDefinition = new CustomizeBeanDefinition();
                                if(aClass.isAnnotationPresent(CustomizeScope.class)){
                                    CustomizeScope customizeScope = aClass.getDeclaredAnnotation(CustomizeScope.class);
                                    beanDefinition.setScope(customizeScope.value().trim());
                                }else{
                                    //如果不设置,默认单例
                                    beanDefinition.setScope("singleton");
                                }
                                beanDefinition.setClazz(aClass);
    
                                beanDefinitionMap.put(beanName,beanDefinition);
                            }
    
                        } catch (ClassNotFoundException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }
    
        /**
         * 初始化所有单例bean
         */
        private void initAllSingleBean(){
            for(Map.Entry<String,CustomizeBeanDefinition> entry : beanDefinitionMap.entrySet()){
                String beanName = entry.getKey();
                CustomizeBeanDefinition beanDefinition =  entry.getValue();
                if("singleton".equals(beanDefinition.getScope())){
                    Object beanObj = createBean(beanDefinition);
                    singleTonMap.put(beanName,beanObj);
                }
            }
        }
    
        /**
         * 截取路径
         *
         * @param absFilePath
         * @return
         */
        private String subFilePath(String absFilePath) {
            if (null == absFilePath) {
                return "";
            }
    
            String subPath = absFilePath.substring(absFilePath.indexOf("com"), absFilePath.indexOf(".class"));
    
            if (subPath.length() > 0) {
                subPath = subPath.replace(File.separator, ".");
            }
            return subPath;
        }
    
        /**
         * 创基bean
         * @param beanDefinition
         * @return
         */
        public Object createBean(CustomizeBeanDefinition beanDefinition){
            Class clazz = beanDefinition.getClazz();
            Object instance = null;
    
            try {
                instance = clazz.getDeclaredConstructor().newInstance();
    
                //依赖注入,给属性赋值
                //获取类中所有属性
                Field[] filelds = clazz.getDeclaredFields();
                for(Field f : filelds){
                    //如果有定义的注入注解
                    if(f.isAnnotationPresent(CustomizeAutowired.class)){
                        //根据属性名去找
                        String fBeanName = f.getName();
    
                        Object fBean = getBean(fBeanName);
                        CustomizeAutowired customizeAutowired = f.getDeclaredAnnotation(CustomizeAutowired.class);
                        if(customizeAutowired.required() && null == fBean){
                            //如果是必须
                            throw new NullPointerException();
                        }
    
                        //由于属性为私有属性,需要通过反射方式赋值,故设置true
                        f.setAccessible(true);
                        //将对象赋值给属性
                        f.set(instance,fBean);
    
                    }
                }
    
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            } catch (NoSuchMethodException e) {
                e.printStackTrace();
            }
            return instance;
        }
    
        /**
         * 获取bean 对象
         *
         * @param name
         * @return
         */
        public Object getBean(String name) {
            if(beanDefinitionMap.containsKey(name)){
                CustomizeBeanDefinition beanDefinition = beanDefinitionMap.get(name.trim());
    
                if("singleton".equals(beanDefinition.getScope())){
                    //如果是单例,从单例池中返回
                    return singleTonMap.get(name);
                }else{
                    //原型模式,创建bean对象
                    return createBean(beanDefinition);
                }
            }else{
                //不存在bean,可自定义异常
                throw new NullPointerException();
            }
        }
    }
        public static void main(String[] args) {
            SpringLoader loaderTest = new SpringLoader();
            loaderTest.test2();
        }
    
        /**
         * 依赖注入测试
         */
        private void test2(){
            CustomizeApplicationContext context = new CustomizeApplicationContext(CustomizeConfig.class);
            UserService userService1 = (UserService) context.getBean("userService");
            userService1.doSomething();
        }

    结果

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  • 原文地址:https://www.cnblogs.com/xiaozhuanfeng/p/14724258.html
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