MVC架构探究及其源码实现(2)-核心组件定义

 博学，切问，近思--詹子知 (https://jameszhan.github.io)

上文中，我们讨论了MVC的架构的基本原理，这里，我们就要开始着手实现一个简单的WEB MVC前端控制器模型。为了实现这个架构的原型，我们必须引入几个新的概念。

1. DispatcherServlet：前端控制器，也是整个架构的核心，负责处理和分发请求。
2. HandlerMapping：处理器映射，他主要包含的是控制器的列表，对于特定的请求，根据HandlerMapping的映射关系，可以找到特定的控制器。最简单的便是url到控制器的映射。
3. HandlerAdapter：对于不同类型的控制器，该类负责把Handler请求处理的结果统一转换成ModelAndView。
4. ModelAndView：包含数据和视图的信息，一般包含视图名，和这个视图需要用的数据，这里的Model大家不要误会为模型的概念,它只不过同时包含视图信息及这个视图需要显示的相关信息而已。
5. ViewResolver：它View名称解析成View对象。
6. View：定义response显示的详细内容。

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(); } }

这几个类由DispatcherServlet管理和控制，以下是它们的序列图:

这些对象需要怎么注入到系统中呢？这里当然少不了配置文件的支持，现在比较流行的MVC框架大多可以使用Spring作为其IOC容器，为了简单起见，我们自己决定模拟Spring简单地实现一个配置管理容器，用于管理我们的各种对象资源。

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2. MVC架构探究及其源码实现(3)-WebApplicationContext
3. MVC架构探究及其源码实现(4)-前端控制器
4. MVC架构探究及其源码实现(5)-相关组件实现
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