自己开发一个简单的mvc框架(类似spring mvc)

清疚 2022-08-22 15:20 197阅读 0赞

先看看controller,这里写了一个UserController

package com.tanlei.controller;
    
    import java.util.HashMap;
    import java.util.Map;
    
    import javax.servlet.http.HttpServletRequest;
    
    import tmvc.framework.annotation.Controller;
    import tmvc.framework.annotation.RequestMapping;
    import tmvc.framework.annotation.RequestParameter;
    
    @Controller(url = "/user")
    public class UserController {
    
    	@RequestMapping(url ="/login.html", method="POST")
    	public String login(@RequestParameter(value="userName") String userName,@RequestParameter(value="request") HttpServletRequest request, @RequestParameter(value="password") String password) {
    		Map<String, Object> map = new HashMap<String, Object>();
    		Map<String, Object> returnMap = new HashMap<String, Object>();
    		map.put("a", "aaaaa");
    		System.out.println("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"); 
    		request.setAttribute("userName", "tanlei");
    		return "index.jsp";
    	}
    }

这里定义了三个注解:@Controller和@RequestMapping和@RequestParameter

package tmvc.framework.annotation;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Target(ElementType.PARAMETER)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface RequestParameter {
    	String value() default "";
    }

package tmvc.framework.annotation;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface RequestMapping {
    	String url() default ""; //描述路径,例如： /article/1,则这里写成 url = /1
    	String method() default "GET";  //用于描述请求方式
    }

package tmvc.framework.annotation;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Controller {
    	String url() default "";
    }

核心流程:

服务器启动，执行ControllerHandlerListener,扫描Contrtoller所在包:com.tanlei.controller,生成MethodHandlerMap并放入ServletContext中:

package tmvc.framework.web;
    
    import java.util.Map;
    
    import javax.servlet.ServletContextEvent;
    import javax.servlet.ServletContextListener;
    
    import tmvc.framework.util.ControllerHandler;
    
    public class ControllerHandleListener implements ServletContextListener {
    	
    	@Override
    	public void contextDestroyed(ServletContextEvent servletContextEvent) {
    		
    		
    	}
    
    	@Override
    	public void contextInitialized(ServletContextEvent servletContextEvent) {
    		try {
    			String controllerPackageName = servletContextEvent.getServletContext().getInitParameter("controllerPackageName");
    			Map<String, Map<String, Object>> methodHandlerMap = ControllerHandler.handle(controllerPackageName);
    			servletContextEvent.getServletContext().setAttribute("methodHandlerMap", ControllerHandler.handle(controllerPackageName));
    			
    		} catch (ClassNotFoundException e) {
    			e.printStackTrace();
    		}
    	}
    
    }

这里的核心是methodHandlerMap这个数据结构。

来看看methodHandlerMap生成方法:

package tmvc.framework.util;
    
    import java.lang.annotation.Annotation;
    import java.lang.reflect.Method;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    import java.util.Set;
    
    import tmvc.framework.annotation.Controller;
    import tmvc.framework.annotation.RequestMapping;
    import tmvc.framework.annotation.RequestParameter;
    
    /**
     * 控制层处理器 反射controller层的包 得到url与controller对应的map，例如 对ShowArticleController处理
     * handlerMap.put("/article/1", map<String, Object>); map.put("1"(二级url),
     * methodName); map.put("1"(二级url), parameterList<Map<"parameterName"，方法参数名>,Map<"parameterType"，方法参数类型>>);
     * 
     * @author Administrator
     *
     */

public class ControllerHandler {
    
    	public static String[] getMethodParameterNamesByAnnotation(Method method) {
    		Annotation[][] parameterAnnotations = method.getParameterAnnotations();
    		if (parameterAnnotations == null || parameterAnnotations.length == 0) {
    			return null;
    		}
    		String[] parameterNames = new String[parameterAnnotations.length];
    		int i = 0;
    		for (Annotation[] parameterAnnotation : parameterAnnotations) {
    			for (Annotation annotation : parameterAnnotation) {
    				if (annotation instanceof RequestParameter) {
    					RequestParameter param = (RequestParameter) annotation;
    					parameterNames[i++] = param.value();
    				}
    			}
    		}
    		return parameterNames;
    	}

public static Map<String, Map<String, Object>> handle(String controllerPackageName) throws ClassNotFoundException {
    		// 控制层的数据封装
    		Map<String, Map<String, Object>> handlerMap = new HashMap<String, Map<String, Object>>();
    
    		// 根据包名反射控制层所有controller
    		Set<String> clazzs = ClassUtil.getClassName(controllerPackageName, false);
    		for (String clazz : clazzs) {
    			Class<?> c = Class.forName(clazz);
    			// 得到头部注解@Controller
    			Controller ct = c.getAnnotation(Controller.class);
    			String url = null;
    			String headerUrl = ct.url();

// 得到方法上的注解@RequestMapping，方法名和方法内的参数(有序)
    			for (Method method : c.getDeclaredMethods()) {
    				Map<String, Object> methodMap = new HashMap<String, Object>();
    				RequestMapping r = method.getAnnotation(RequestMapping.class);
    				String methodUrl = r.url();
    				url = headerUrl + methodUrl;
    				Class<?> paramTypes[] = method.getParameterTypes();
    				String[] paramNames = getMethodParameterNamesByAnnotation(method);
    				List<Map<String , Object>> params = new ArrayList<Map<String, Object>>();
    				for (int i = 0; i < paramTypes.length; i++) {
    					Map<String, Object> paramMap = new HashMap<String, Object>();
    					paramMap.put("paramName", paramNames[i]);
    					paramMap.put("paramType", paramTypes[i]);
    					params.add(paramMap);
    				}
    				methodMap.put("url", clazz);
    				methodMap.put("params", params);
    				methodMap.put("methodName", method.getName());
    				handlerMap.put(url, methodMap);
    				
    			}
    		}
    		return handlerMap;
    	}
    
    
    }

ControllerHandler这个类负责扫描Controller所在包的所有类，生成类的反射信息封装在map中。

以UserController为例：

Map<String, Map<String, Object>>的内层map负责 innermap.put("url", com.tanlei.controller.UserController), innermap.put("params", params),

params为一个List<Map<String , Object>> params = new ArrayList<Map<String, Object>>();类型。里面存放的是方法的参数名和类型的信息

例如UserController的login方法参数信息。

innermap.put("methodName", method.getName());

然后外层outermap.put(url, methodMap); url为: /user/login.html,即方法controller和requestMaping的映射信息。

核心dispatcherServlet类负责转发请求给controller和返回到页面：

package tmvc.framework.web;
    
    import java.io.IOException;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.util.List;
    import java.util.Map;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import tmvc.framework.util.ClassUtil;
    import tmvc.framework.util.UriUtil;
    
    /**
     * Servlet implementation class DispatcherServlet
     */
    @WebServlet("/DispatcherServlet")
    public class DispatcherServlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;    
        
    	public void init() throws ServletException {
    
    	}

public void service(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
    			throws ServletException, IOException, RuntimeException {
        	//反射得到对应的controller 
        	Map<String, Map<String, Object>> methodHandlerMap = (Map<String, Map<String, Object>>) this.getServletContext().getAttribute("methodHandlerMap");
        	String uri = httpServletRequest.getRequestURI().toString();
    
        	Map<String, Object> methodMap = methodHandlerMap.get(UriUtil.getControllerUri(httpServletRequest,uri));
        	String queryStr = httpServletRequest.getQueryString();
        	System.out.println(uri+ ":" +  httpServletRequest.getContextPath().length());
        	List<Map<String , Object>> params = (List<Map<String, Object>>) methodMap.get("params"); //反射方法得到的参数信息的list
        	Object[] paramObjs = new Object[params.size()];//method的参数值的集合

Class[] paramTypes = new Class[params.size()];//method的参数类型的集合
        	int index = 0;
        	//List<Map<String , String>> urlParams = RequestParameterHandler.generateParameterListMap(httpServletRequest); //url里面传来的参数的list
        	for(int i = 0; i < params.size(); i++) {
        		Map<String, Object> paramMap = params.get(i); //反射得到的参数map
        		paramTypes[i] = (Class) paramMap.get("paramType");
        		String paramName = (String) paramMap.get("paramName");
        		if(paramTypes[i].isInstance(httpServletRequest)) {
        			paramObjs[i] = httpServletRequest;
        		} else {
        			paramObjs[i] = httpServletRequest.getParameter(paramName);
        		}
        	}

try {
    			Class<?> clazz = Class.forName((String)methodMap.get("url"));
    			Method method = clazz.getDeclaredMethod((String)methodMap.get("methodName"), paramTypes);
    			Object obj = clazz.newInstance();
    			Object ob = method.invoke(obj, paramObjs);
    			System.out.println(ob.toString());
    			httpServletRequest.getRequestDispatcher("/" + ob.toString()).forward(httpServletRequest, httpServletResponse);
    			return;
    			
    		} catch (ClassNotFoundException | NoSuchMethodException e) {
    			e.printStackTrace();
    		} catch (InstantiationException e) {
    			e.printStackTrace(); 
    		} catch (IllegalAccessException e) {
    			e.printStackTrace();
    		} catch (InvocationTargetException e) {
    			e.printStackTrace();
    		}
        }

urlutil:

package tmvc.framework.util;
    
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    import javax.servlet.http.HttpServletRequest;
    
    public class UriUtil {
    	
    	public static String getControllerUri(HttpServletRequest request, String uri) {
    		if(uri.contains("?")) {
        		uri = uri.substring(request.getContextPath().length(), uri.indexOf("?"));
        	} else {
        		uri = uri.substring(request.getContextPath().length(), uri.length());
        	}
    		return uri;
    	}
    	
    	
    
    	
    }

classutil核心方法:

public static Set<String> getClassName(String packageName, boolean isRecursion) {
            Set<String> classNames = null;
            ClassLoader loader = Thread.currentThread().getContextClassLoader();
            String packagePath = packageName.replace(".", "/");
    
            URL url = loader.getResource(packagePath);
            if (url != null) {
                String protocol = url.getProtocol();
                if (protocol.equals("file")) {
                    classNames = getClassNameFromDir(url.getPath(), packageName, isRecursion);
                } else if (protocol.equals("jar")) {
                    JarFile jarFile = null;

try{
                        jarFile = ((JarURLConnection) url.openConnection()).getJarFile();
                    } catch(Exception e){
                        e.printStackTrace();
                    }
                    
                    if(jarFile != null){
                        getClassNameFromJar(jarFile.entries(), packageName, isRecursion);
                    }
                }
            } else {
                /*从所有的jar包中查找包名*/
                classNames = getClassNameFromJars(((URLClassLoader)loader).getURLs(), packageName, isRecursion);
            }
            
            return classNames;
        }

web.xml的配置:

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:jsp="http://java.sun.com/xml/ns/javaee/jsp" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
      <display-name>test</display-name>
    
      <context-param>
        <param-name>controllerPackageName</param-name>
        <param-value>com.tanlei.controller</param-value>
      </context-param>
    
      <listener>
      	<listener-class>tmvc.framework.web.ControllerHandleListener</listener-class>
      </listener>

<servlet>
        <servlet-name>dispatcherServlet</servlet-name>
        <servlet-class>tmvc.framework.web.DispatcherServlet</servlet-class>
        <init-param>
          <param-name>controllerPackageName</param-name>
          <param-value>com.tanlei.controller</param-value>
        </init-param>
      </servlet>
      <servlet-mapping>
        <servlet-name>dispatcherServlet</servlet-name>
        <url-pattern>*.html</url-pattern>
      </servlet-mapping>
    </web-app>

访问:http://localhost:8080/user/login.html?userName=a&password=b访问成功，页面跳转。

只是实现了一个简单的流程，还有很多细节没有实现。

由于公司限制复制内容大小，限制网络等原因，代码格式不好，以后完善后给出下载链接。