java提高篇之框架

1.spring框架

为了入门，可以参照一下链接:

https://blog.csdn.net/u010013573/article/details/86547687

要看spring源码之前先思考spring和servlet是怎么挂钩的？，在servlet规范中,servlet容器例如:tomcat，每个容器可以有很多个应用,每个应用都有对应的servletContext,这个在项目启动的时候,回去读取web.xml加载listener、filter、servlet的信息，

初始化servletContext的时候,会生成ServletContextEvent,方法中会有servletContext的引用

public class ServletContextEvent extends EventObject {
    private static final long serialVersionUID = 1L;

    public ServletContextEvent(ServletContext source) {
        super(source);
    }

    public ServletContext getServletContext() {
        return (ServletContext)super.getSource();
    }
}

然后这个ServletContextEvent会传到ServletContextListener中（web.xml中的加载顺序：context-param -> listener -> filter -> servlet）

public interface ServletContextListener extends EventListener {
    default void contextInitialized(ServletContextEvent sce) {
　　//我们spring就是在这个初始化方法做一些数据库连接、bean容器等组件,此时filter和servlet还没有初始化,所以初始化的时候，就可以用到spring的组件了
    }

    default void contextDestroyed(ServletContextEvent sce) {
    }
}

看看Spring实现了ServletContextListener 的ContextLoaderListener （属于listener顺序）

public class ContextLoaderListener extends ContextLoader implements ServletContextListener {
    public ContextLoaderListener() {
    }

    public ContextLoaderListener(WebApplicationContext context) {
        super(context);
    }

    public void contextInitialized(ServletContextEvent event) {
        this.initWebApplicationContext(event.getServletContext());
    }

    public void contextDestroyed(ServletContextEvent event) {
        this.closeWebApplicationContext(event.getServletContext());
        ContextCleanupListener.cleanupAttributes(event.getServletContext());
    }
}

2.springMVC

看springMVC源码核心的是看 DispatcherServlet，我参照别人看了源码,相对比较简单

https://blog.csdn.net/gududedabai/article/details/83352106

public class DispatcherServlet extends FrameworkServlet ..

public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware 

最终还是实现Servlet,我们从servlet的service入口方法看起,在子类FrameworkServlet中

protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpMethod httpMethod = HttpMethod.resolve(request.getMethod());
        if (httpMethod != HttpMethod.PATCH && httpMethod != null) {
            super.service(request, response);
        } else {
            this.processRequest(request, response);//只要不是HttpMethod.PATCH方式就会调用

} }

protected final void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    ...

        this.doService(request, response);
　　...

}

doService方法会在DispatcherServlet中实现,这里已经进入SpringMVC了,之前都是servlet规范,所以SpringMVC也是要遵循Servlet规范的

protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
    ...
            this.doDispatch(request, response);核心在这里,
    ...
}       



//最核心的代码在这里

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
    HttpServletRequest processedRequest = request;
    HandlerExecutionChain mappedHandler = null;
    boolean multipartRequestParsed = false;
    WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

    try {
        try {
            ModelAndView mv = null;
            Object dispatchException = null;

            try {
                processedRequest = this.checkMultipart(request);
                multipartRequestParsed = processedRequest != request;
                mappedHandler = this.getHandler(processedRequest);//获取handler
                if (mappedHandler == null) {
                    this.noHandlerFound(processedRequest, response);
                    return;
                }

                HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());//获取适配器,例如注解的、xml,一共有三种,在springMVC包里面的DispatcherServlet.properties有配置


                String method = request.getMethod();
                boolean isGet = "GET".equals(method);
                if (isGet || "HEAD".equals(method)) {
                    long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
                    if ((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {
                        return;
                    }
                }

                if (!mappedHandler.applyPreHandle(processedRequest, response)) {
                    return;
                }

                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());//执行handler,返回视图
                if (asyncManager.isConcurrentHandlingStarted()) {
                    return;
                }

                this.applyDefaultViewName(processedRequest, mv);
                mappedHandler.applyPostHandle(processedRequest, response, mv);
            } catch (Exception var20) {
                dispatchException = var20;
            } catch (Throwable var21) {
                dispatchException = new NestedServletException("Handler dispatch failed", var21);
            }

            this.processDispatchResult(processedRequest, response, mappedHandler, mv, (Exception)dispatchException);
        } catch (Exception var22) {
            this.triggerAfterCompletion(processedRequest, response, mappedHandler, var22);
        } catch (Throwable var23) {
            this.triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException("Handler processing failed", var23));
        }

    } finally {
        if (asyncManager.isConcurrentHandlingStarted()) {
            if (mappedHandler != null) {
                mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
            }
        } else if (multipartRequestParsed) {
            this.cleanupMultipart(processedRequest);
        }

    }
}

　参照: https://www.cnblogs.com/diandianquanquan/p/10965047.html

3.springBoot

参照: https://blog.csdn.net/weixin_34128501/article/details/92424885

参照: https://blog.csdn.net/hongtaolong/article/details/104886913 这个有点用处,让你知道启动的时候调用到tomcat的流程

4.springcCoud

5.Mybatis

参考:

https://blog.csdn.net/cheng_1017/article/details/112600890

6.Dubbo