一览SpringMvc请求流程源码，解析SpringMvc的奥秘！

SpringMVC请求流程源码解析

SpringMVC是一种流行的Java Web框架，它使得Web开发更加容易。SpringMVC的请求处理流程非常重要，它决定了请求是如何被处理的。

SpringMVC的请求处理流程主要由以下几个组件组成：

• DispatcherServlet：DispatcherServlet是SpringMVC的核心组件，它负责接收请求并将其分发给适当的处理程序。
• HandlerMapping：HandlerMapping负责将请求映射到相应的处理器。
• HandlerAdapter：HandlerAdapter负责将处理器适配到SpringMVC的执行环境中。
• Controller：Controller负责处理请求并生成响应。
• ModelAndView：ModelAndView包含了视图和模型数据。
• ViewResolver：ViewResolver负责将ModelAndView解析成View。
• View：View负责渲染ModelAndView中的模型数据并将其发送给浏览器。

SpringMVC的请求处理流程如下：

1. DispatcherServlet收到请求。
2. DispatcherServlet将请求交给HandlerMapping处理。
3. HandlerMapping将请求映射到相应的处理器。
4. DispatcherServlet将处理器交给HandlerAdapter处理。
5. HandlerAdapter将处理器适配到SpringMVC的执行环境中。
6. Controller处理请求并生成响应。
7. Controller将响应封装在ModelAndView中。
8. DispatcherServlet将ModelAndView交给ViewResolver处理。
9. ViewResolver将ModelAndView解析成View。
10. View负责渲染ModelAndView中的模型数据并将其发送给浏览器。

以下是一个SpringMVC请求处理流程的代码示例：

public class SpringMvcRequestProcessor {

    private DispatcherServlet dispatcherServlet;

    public SpringMvcRequestProcessor(DispatcherServlet dispatcherServlet) {
        this.dispatcherServlet = dispatcherServlet;
    }

    public void processRequest(HttpServletRequest request, HttpServletResponse response) {
        // DispatcherServlet收到请求
        dispatcherServlet.service(request, response);
    }
}

public class DispatcherServlet {

    private HandlerMapping handlerMapping;

    private HandlerAdapter handlerAdapter;

    public DispatcherServlet(HandlerMapping handlerMapping, HandlerAdapter handlerAdapter) {
        this.handlerMapping = handlerMapping;
        this.handlerAdapter = handlerAdapter;
    }

    public void service(HttpServletRequest request, HttpServletResponse response) {
        // DispatcherServlet将请求交给HandlerMapping处理
        HandlerExecutionChain handlerExecutionChain = handlerMapping.getHandler(request);

        // DispatcherServlet将处理器交给HandlerAdapter处理
        ModelAndView modelAndView = handlerAdapter.handle(request, response, handlerExecutionChain.getHandler());

        // DispatcherServlet将响应封装在ModelAndView中
        ViewResolver viewResolver = new ViewResolver();
        View view = viewResolver.resolveViewName(modelAndView.getViewName());

        // DispatcherServlet将ModelAndView交给ViewResolver处理
        view.render(modelAndView.getModel(), request, response);
    }
}

public class HandlerMapping {

    public HandlerExecutionChain getHandler(HttpServletRequest request) {
        // HandlerMapping将请求映射到相应的处理器
        HandlerExecutionChain handlerExecutionChain = new HandlerExecutionChain();
        handlerExecutionChain.setHandler(new MyController());
        return handlerExecutionChain;
    }
}

public class HandlerAdapter {

    public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        // HandlerAdapter将处理器适配到SpringMVC的执行环境中
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("myView");
        return modelAndView;
    }
}

public class Controller {

    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
        // Controller处理请求并生成响应
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("myView");
        return modelAndView;
    }
}

public class ModelAndView {

    private String viewName;

    private Map<String, Object> model;

    public ModelAndView() {
        this.model = new HashMap<>();
    }

    public ModelAndView(String viewName) {
        this();
        this.viewName = viewName;
    }

    public String getViewName() {
        return viewName;
    }

    public void setViewName(String viewName) {
        this.viewName = viewName;
    }

    public Map<String, Object> getModel() {
        return model;
    }

    public void setModel(Map<String, Object> model) {
        this.model = model;
    }
}

public class ViewResolver {

    public View resolveViewName(String viewName) {
        // ViewResolver将ModelAndView解析成View
        View view = new MyView();
        return view;
    }
}

public class View {

    public void render(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) {
        // View负责渲染ModelAndView中的模型数据并将其发送给浏览器
        PrintWriter writer = response.getWriter();
        writer.write("<html><body>");
        for (Map.Entry<String, Object> entry : model.entrySet()) {
            writer.write(entry.getKey() + ": " + entry.getValue() + "<br>");
        }
        writer.write("</body></html>");
    }
}