手写Spring框架

矫情吗；* 2021-10-15 06:27 422阅读 0赞

### 项目结构 ###

├── pom.xml
    ├── spring-demo.iml
    ├── src
       └── main
           ├── java
           │   └── xyz
           │       └── suiwo
           │           ├── action
           │           │   ├── controller
           │           │   │   └── DemoController.java
           │           │   └── service
           │           │       ├── DemoService.java
           │           │       └── impl
           │           │           └── DemoServiceImpl.java
           │           └── framework
           │               ├── annotation
           │               │   ├── SWAutowried.java
           │               │   ├── SWController.java
           │               │   ├── SWRequestMapping.java
           │               │   ├── SWRequestParam.java
           │               │   └── SWService.java
           │               └── servlet
           │                   └── SWDispatcherServlet.java
           ├── resources
           │   └── application.properties
           └── web
               ├── WEB-INF
               │   └── web.xml
               └── index.jsp

### 所用依赖 ###

<dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>${servlet.api.version}</version>
        <scope>provided</scope>
    </dependency>

### web.xml配置如下 ###

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0">
        <display-name>Suiwo Web Application</display-name>
        <servlet>
            <servlet-name>swmvc</servlet-name>
            <servlet-class>xyz.suiwo.framework.servlet.SWDispatcherServlet</servlet-class>
            <init-param>
                <param-name>contextConfigLocation</param-name>
                <param-value>application.properties</param-value>
            </init-param>
            <load-on-startup>1</load-on-startup>
        </servlet>
        <servlet-mapping>
            <servlet-name>swmvc</servlet-name>
            <url-pattern>/*</url-pattern>
        </servlet-mapping>
    </web-app>

### application.properties配置如下 ###

scanPackage=xyz.suiwo.action

### 下面是几个我们自定义的注解类 ###

@Target({ ElementType.FIELD})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface SWAutowried { 
        String value() default "";
    }

@Target({ ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface SWController { 
        String value() default "";
    }

@Target({ ElementType.TYPE, ElementType.METHOD})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface SWRequestMapping { 
        String value() default "";
    }

@Target({ ElementType.PARAMETER})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface SWRequestParam { 
        String value() default "";
    }

@Target({ ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface SWService { 
        String value() default "";
    }

### 下面我们新建几个controller类和service类并使用我们自定义的注解 ###

@SWController
    @SWRequestMapping("/get")
    public class DemoController { 
    
        @SWAutowried
        DemoService demoService;
    
        @SWRequestMapping("/method")
        public void get(HttpServletRequest request, HttpServletResponse response,
                        @SWRequestParam("name") String name){ 
            demoService.get();
            try { 
                response.getWriter().write("my name is " + name);
            } catch (IOException e) { 
                e.printStackTrace();
            }
        }
    }

public interface DemoService { 
        void get();
    }

@SWService
    public class DemoServiceImpl implements DemoService { 
        public void get() { 
            System.out.println("This is method get");
        }
    }

最后让我们看一下我们的Dispatcher类

public class SWDispatcherServlet extends HttpServlet { 
    
        private Properties properties = new Properties();
    
        private List<String> classNames = new ArrayList<>();
    
        private Map<String, Object> ioc = new HashMap<>();
    
        private Map<String, Method> handlerMapping = new HashMap<>();
    
    
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            doDispatch(req,resp);
    
            //注：当使用父类的doGet以及doPost可能会导致405错误
    // super.doGet(req, resp);
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) { 
            doDispatch(req,resp);
    // doDispatch(req, resp);
        }
    
        @Override
        public void init(ServletConfig config)  { 
            //1.加载配置文件
            doLoadConfig(config.getInitParameter("contextConfigLocation"));
    
            //2.扫描所有相关的类
            doScanner(properties.getProperty("scanPackage"));
    
            //3.初始化所有相关Class的实例，并且将其保存到IOC容器中
            doInstance();
    
            //4.自动化的依赖注入
            doAutowired();
    
            //5.初始化handlerMapping
            initHandlerMapping();
    
            System.out.println("初始化成功");
        }
    
        private void doLoadConfig(String location) { 
    
            InputStream inputStream =null;
            try { 
                inputStream = this.getClass().getClassLoader().getResourceAsStream(location);
                properties.load(inputStream);
            } catch (IOException e) { 
                e.printStackTrace();
            } finally { 
                try { 
                    if (null != inputStream) { 
                        inputStream.close();
                    }
                } catch (IOException e) { 
                    e.printStackTrace();
                }
            }
        }
    
        //进行扫描
        private void doScanner(String packageName) { 
            URL url = this.getClass().getClassLoader()
                    .getResource("/" + packageName.replaceAll("\\.", "/"));
            File classDir = new File(Objects.requireNonNull(url).getFile());
            for(File file : Objects.requireNonNull(classDir.listFiles())){ 
    
                //递归获取scan下所有的类，并将类名添加至classNames中用于之后实例化
                if(file.isDirectory()){ 
                    doScanner(packageName + "." + file.getName());
                }else { 
                    String className = packageName + "." + file.getName().replace(".class","").trim();
                    classNames.add(className);
                }
            }
    
        }
    
        //进行实例化
        private void doInstance() { 
            if(classNames.isEmpty()){ 
                return;
            }
            for(String className : classNames){ 
                try { 
                    Class<?> clazz = Class.forName(className);
    
                    //进行实例化
                    //判断不是所有的都需要实例化，只有添加了例如Controller或者Service的注解才初始化
                    if(clazz.isAnnotationPresent(SWController.class)){ 
                        //beanName beanId
                        //1.默认采用类名的首字母小写
                        //2.如果自定义了名字，默认使用自定义名字
                        //3.根据类型匹配，利用实现类的接口名作为Key
                        String beanName = toLowStr(clazz.getSimpleName());
                        ioc.put(beanName, clazz.newInstance());
                    }else if(clazz.isAnnotationPresent(SWService.class)){ 
                        SWService swService = clazz.getAnnotation(SWService.class);
                        String beanName = swService.value();
                        if(!"".equals(beanName.trim())){ 
                            ioc.put(beanName, clazz.newInstance());
                            continue;
                        }
    
                        //获取对象所实现的所有接口
                        Class<?>[] interfaces = clazz.getInterfaces();
                        for(Class<?> i : interfaces){ 
                            ioc.put(i.getName(), clazz.newInstance());
                        }
                    }
                } catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) { 
                    e.printStackTrace();
                }
    
    
            }
        }
    
        private void doAutowired() { 
            if(ioc.isEmpty()){ 
                return;
            }
    
            for (Map.Entry<String, Object> entry : ioc.entrySet()){ 
                //在spring中没有隐私
                //咱们只认 @Autowried，获取所有属性
                Field[] fields = entry.getValue().getClass().getDeclaredFields();
    
                for(Field field : fields){ 
                    if(!field.isAnnotationPresent(SWAutowried.class)){ 
                        continue;
                    }
    
                    SWAutowried swAutowried = field.getAnnotation(SWAutowried.class);
    
                    String beanName = swAutowried.value().trim();
                    //如果为空说明使用默认名字，所以使用getName获取默认名字
                    if("".equals(beanName)){ 
                        beanName = field.getType().getName();
                    }
    
                    field.setAccessible(true);
    
                    try { 
                        //向属性set进已经实例化的对象
                        field.set(entry.getValue(), ioc.get(beanName));
                    } catch (IllegalAccessException e) { 
                        e.printStackTrace();
                    }
                }
            }
    
        }
    
        private void initHandlerMapping() { 
            if(!ioc.isEmpty()){ 
                for(Map.Entry<String, Object> entry : ioc.entrySet()){ 
                    Class<?> clazz = entry.getValue().getClass();
                    //HandlerMapping只认识SWController
                    if(!clazz.isAnnotationPresent(SWController.class)){ 
                        continue;
                    }
                    String url = "";
                    //获取类上的RequestMapping地址
                    if(clazz.isAnnotationPresent(SWRequestMapping.class)){ 
                        SWRequestMapping swRequestMapping = clazz.getAnnotation(SWRequestMapping.class);
                        url = swRequestMapping.value();
                    }
                    Method[] methods = clazz.getMethods();
                    for(Method method : methods){ 
                        if(!method.isAnnotationPresent(SWRequestMapping.class)){ 
                            continue;
                        }
                        //获取实际方法上的requestMapping
                        SWRequestMapping swRequestMapping = method.getAnnotation(SWRequestMapping.class);
                        String mUrl = url + swRequestMapping.value();
                        handlerMapping.put(mUrl, method);
                        System.out.println("Mapping : " + mUrl + " " + method);
                    }
    
                }
            }
        }
    
        private void doDispatch(HttpServletRequest request, HttpServletResponse response) { 
            String url = request.getRequestURI();
            String contextPath = request.getContextPath();
            url = url.replace(contextPath, "").replaceAll("/+", "/");
            if(!handlerMapping.containsKey(url)){ 
                try { 
                    response.getWriter().write("404");
                    return;
                } catch (IOException e) { 
                    e.printStackTrace();
                }
            }
            //获取当前路由对应的方法
            Method method = handlerMapping.get(url);
            System.out.println("获得对应的方法" + method);
    
            //获取方法列表
            Class<?>[] parameterTypes = method.getParameterTypes();
            Map<String, String[]> parameterMap = request.getParameterMap();
    
            Object[] paramValues = new Object[parameterTypes.length];
            for(int i = 0; i < parameterTypes.length; i++){ 
                Class parameterType = parameterTypes[i];
                if(parameterType == HttpServletRequest.class){ 
                    paramValues[i] = request;
                    continue;
                }else if(parameterType == HttpServletResponse.class){ 
                    paramValues[i] = response;
                }else if(parameterType == String.class){ 
                    for(Map.Entry<String, String[]> entry : parameterMap.entrySet()){ 
                        String value = Arrays.toString(entry.getValue()).replaceAll("\\[|\\]","")
                                .replaceAll(",\\s", ",");
                        paramValues[i++] = value;
                        if(i == parameterTypes.length){ 
                            break;
                        }
                    }
                }
            }
            try{ 
                String beanName = toLowStr(method.getDeclaringClass().getSimpleName());
                method.invoke(this.ioc.get(beanName), paramValues);
            }catch (Exception e){ 
                e.printStackTrace();
            }
        }
    
        private String toLowStr(String str){ 
            char[] ch = str.toCharArray();
            ch[0] += 32;
            return String.valueOf(ch);
        }
    }

> 此时我们就可以在浏览器中访问对应的网页了，至此一个简易的Spring框架就完成了

项目链接：[https://github.com/ZhangJia97/Spring-demo][https_github.com_ZhangJia97_Spring-demo]

[https_github.com_ZhangJia97_Spring-demo]: https://github.com/ZhangJia97/Spring-demo