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。

相关文章:

1. MVC架构探究及其源码实现(1)-理论基础
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
5. MVC架构探究及其源码实现(6)-简单示例