先看整體架構
因爲我們這個 MVC 框架要依賴 IOC/DI 容器，所以我們在 pom 文件裏要將自己的 Spring 框架引入進來。
實現 MVC 的整體功能
首先我們定義兩個 MVC 專用的註解，RequestMapping 用來做 url 匹配，RequestParam 做參數轉換：
package com.paul.annotation;import java.lang.annotation.*;
@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestMapping { String value() default "";
}package com.paul.annotation;import java.lang.annotation.*;@Target(ElementType.PARAMETER)@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface RequestParam { String value() default "";
}我們知道 SpringMVC 的核心是 DispatcherServlet，用來做核心路由控制，我們也定義這樣一個類，並且在初始化方法裏初始化一個 IOC/DI 容器，看過前面文章的同學應該知道，初始化容器後我們已經將 Bean 放到容器中而且完成了依賴注入。
package com.paul.servlet;import com.paul.annotation.RequestMapping;import com.paul.annotation.RequestParam;import org.springframework.ioc.annotation.Controller;import org.springframework.ioc.bean.AnnotationApplicationContext;import org.springframework.ioc.bean.ApplicationContext;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.lang.annotation.Annotation;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;//實現 servlet，和我們以前使用 servlet 一樣。public class DispatcherServlet extends HttpServlet { // 完整路徑和 方法的 mapping
private Map<String,Object> handleMapping = new ConcurrentHashMap<>(); // 類路徑和controller 的 mapping
private Map<String,Object> controllerMapping = new ConcurrentHashMap<>();
private Map<String,Object> beanFactory = new ConcurrentHashMap<>();
@Override
public void init(ServletConfig config) throws ServletException { super.init(config); //實例化 IOC 容器
ApplicationContext ctx = new AnnotationApplicationContext("applicationContext.xml"); this.beanFactory = ((AnnotationApplicationContext) ctx).beanFactory; //上一步已經完成了 Controller，service，respostry，autowired 等註解的掃描和注入
//遍歷容器，將 requestmapping 註解的路徑和對應的方法以及 contoller 實例對應起來
for(Map.Entry<String,Object> entry:beanFactory.entrySet()){ Object instance = entry.getValue();
Class<?> clazz = instance.getClass(); if(clazz.isAnnotationPresent(Controller.class)){
RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class); String classPath = requestMapping.value();
Method[] methods = clazz.getMethods(); for(Method method:methods){ if(method.isAnnotationPresent(RequestMapping.class)){
RequestMapping requestMapping2 = method.getAnnotation(RequestMapping.class); String methodPath = requestMapping2.value(); String requestPath = classPath + methodPath;
handleMapping.put(requestPath,method);
controllerMapping.put(requestPath,instance);
}else{ continue;
}
}
}else{ continue;
}
}
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doPost(req, resp);
} //根據上一步獲取到的 mapping，根據 url 找到對應的 controller 和方法去執行。
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String uri = req.getRequestURI(); // /paul-mvc/com.paul.controller/method-com.paul.controller
String context = req.getContextPath(); // /paul-vmc
String path = uri.replace(context,""); // /com.paul.controller/method-com.paul.controller
Method m = (Method) handleMapping.get(path); //從容器裏拿到controller 實例
Object instance = controllerMapping.get(path); Object[] args = handle(req,resp,m); for (Object a:args){
System.out.println("Object:"+a);
} try {
m.invoke(instance,args);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
private static Object[] handle(HttpServletRequest req, HttpServletResponse resp,Method method){ //拿到當前執行的方法有哪些參數
Class<?>[] paramClazzs = method.getParameterTypes(); //根據參數的個數，new 一個參數的數據
Object[] args = new Object[paramClazzs.length];
int args_i = 0;
int index = 0; for(Class<?> paramClazz:paramClazzs){ if(ServletRequest.class.isAssignableFrom(paramClazz)){
args[args_i++] = req;
} if(ServletResponse.class.isAssignableFrom(paramClazz)){
args[args_i++] = resp;
} //判斷requestParam 註解
Annotation[] paramAns = method.getParameterAnnotations()[index]; if(paramAns.length > 0){
System.out.println("my"); for(Annotation paramAn:paramAns){ if(RequestParam.class.isAssignableFrom(paramAn.getClass())){
System.out.println("13mj");
RequestParam rp = (RequestParam) paramAn;
args[args_i++] = req.getParameter(rp.value());
}
}
}
index ++;
} return args;
}
}測試代碼
新建一個 WebDemo，Maven web 項目。
先來看我們需要測試的 Controller 和 Service。
@Controller@RequestMapping("/user")public class UserController { @Autowired
private UserService userService; @RequestMapping("/query") public void get(HttpServletRequest request, HttpServletResponse response, @RequestParam("name") String name,@RequestParam("age") String age){ try {
PrintWriter pw = response.getWriter();
String res = userService.query(name,age);
pw.write(res);
} catch (IOException e) {
e.printStackTrace();
}
}
}import org.springframework.ioc.annotation.Service;@Service("userService")public class UserServiceImpl implements UserService { @Override
public String query(String name, String age) { return "name="+name+"age="+age;
}
}在 resources 目錄我們需要寫一個名字爲 applicationContext 的配置文件來指明掃描包路徑。
<?xml version="1.0" encoding="UTF-8"?><beans> <package-scan component-scan="com.paul.demo" /></beans>
在 web.xml 中配置我們自己的 DispatcherServlet。
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd" ><web-app> <display-name>Archetype Created Web Application</display-name> <servlet> <servlet-name>DispatcherServlet</servlet-name> <servlet-class>com.paul.servlet.DispatcherServlet</servlet-class> <load-on-startup>0</load-on-startup> </servlet> <servlet-mapping> <servlet-name>DispatcherServlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping></web-app>
在瀏覽器中測試結果：
結果和我們想的一樣。