MVC架構探究及其源碼實現(2)-核心組件定義

 博學，切問，近思--詹子知 (https://jameszhan.github.io)

上文中，我們討論了MVC的架構的基本原理，這裏，我們就要開始着手實現一個簡單的WEB MVC前端控制器模型。爲了實現這個架構的原型，我們必須引入幾個新的概念。

1. DispatcherServlet：前端控制器，也是整個架構的核心，負責處理和分發請求。
2. HandlerMapping：處理器映射，他主要包含的是控制器的列表，對於特定的請求，根據HandlerMapping的映射關係，可以找到特定的控制器。最簡單的便是url到控制器的映射。
3. HandlerAdapter：對於不同類型的控制器，該類負責把Handler請求處理的結果統一轉換成ModelAndView。
4. ModelAndView：包含數據和視圖的信息，一般包含視圖名，和這個視圖需要用的數據，這裏的Model大家不要誤會爲模型的概念,它只不過同時包含視圖信息及這個視圖需要顯示的相關信息而已。
5. ViewResolver：它View名稱解析成View對象。
6. View：定義response顯示的詳細內容。

 

HandlerMapping:package com.google.mvc.web.servlet; import javax.servlet.http.HttpServletRequest; public interface HandlerMapping { String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class.getName() + ".pathWithinHandlerMapping"; Object getHandler(HttpServletRequest request) throws Exception; }  HandlerAdapter:package com.google.mvc.web.servlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public interface HandlerAdapter { boolean supports(Object handler); ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception; long getLastModified(HttpServletRequest request, Object handler); }  ViewResolver:package com.google.mvc.web.servlet; public interface ViewResolver { View resolveViewName(String viewName) throws Exception; }  View: package com.google.mvc.web.servlet; import java.util.Map; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public interface View { String getContentType(); void render(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception; } ModelAndView:package com.google.mvc.web.servlet; import java.util.HashMap; import java.util.Map; public class ModelAndView { private Object view; private Map<String, Object> model; private boolean cleared; public ModelAndView() { } public ModelAndView(String viewName) { this.view = viewName; } public ModelAndView(View view) { this.view = view; } public ModelAndView(String viewName, Map<String, Object> model) { this.view = viewName; if (model != null) { addAllObjects(model); } } public ModelAndView(View view, Map<String, Object> model) { this.view = view; if (model != null) { addAllObjects(model); } } public ModelAndView(String viewName, String modelName, Object modelObject) { this.view = viewName; addObject(modelName, modelObject); } public ModelAndView(View view, String modelName, Object modelObject) { this.view = view; addObject(modelName, modelObject); } public void setViewName(String viewName) { this.view = viewName; } public String getViewName() { return (this.view instanceof String ? (String) this.view : null); } public void setView(View view) { this.view = view; } public View getView() { return (this.view instanceof View ? (View) this.view : null); } public boolean hasView() { return (this.view != null); } public boolean isReference() { return (this.view instanceof String); } protected Map<String, Object> getModelInternal() { return this.model; } public Map<String, Object> getModelMap() { if (this.model == null) { this.model = new HashMap<String, Object>(); } return this.model; } public Map<String, Object> getModel() { return getModelMap(); } public ModelAndView addObject(String attributeName, Object attributeValue) { getModelMap().put(attributeName, attributeValue); return this; } public ModelAndView addObject(Object attributeValue) { getModelMap().put(attributeValue.toString(), attributeValue); return this; } public ModelAndView addAllObjects(Map<String, Object> modelMap) { getModelMap().putAll(modelMap); return this; } public void clear() { this.view = null; this.model = null; this.cleared = true; } public boolean isEmpty() { return (this.view == null && this.model == null); } public boolean wasCleared() { return (this.cleared && isEmpty()); } public String toString() { StringBuffer buf = new StringBuffer("ModelAndView: "); if (isReference()) { buf.append("reference to view with name '").append(this.view).append("'"); } else { buf.append("materialized View is [").append(this.view).append(']'); } buf.append("; model is ").append(this.model); return buf.toString(); } }

這幾個類由DispatcherServlet管理和控制，以下是它們的序列圖:

這些對象需要怎麼注入到系統中呢？這裏當然少不了配置文件的支持，現在比較流行的MVC框架大多可以使用Spring作爲其IOC容器，爲了簡單起見，我們自己決定模擬Spring簡單地實現一個配置管理容器，用於管理我們的各種對象資源。

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1. MVC架構探究及其源碼實現(1)-理論基礎
2. MVC架構探究及其源碼實現(3)-WebApplicationContext
3. MVC架構探究及其源碼實現(4)-前端控制器
4. MVC架構探究及其源碼實現(5)-相關組件實現
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