深度长文回顾web基础组件 （二）

@HandlesTypes({WebApplicationInitializer.class})
public class SpringServletContainerInitializer implements ServletContainerInitializer {
    public SpringServletContainerInitializer() {
    }
    public void onStartup(@Nullable Set<Class<?>> webAppInitializerClasses, ServletContext servletContext) throws ServletException {
        List<WebApplicationInitializer> initializers = new LinkedList();
        Iterator var4;
        if (webAppInitializerClasses != null) {
            var4 = webAppInitializerClasses.iterator();
            while(var4.hasNext()) {
                Class<?> waiClass = (Class)var4.next();
                if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) && WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
                    try {
                        initializers.add((WebApplicationInitializer)ReflectionUtils.accessibleConstructor(waiClass, new Class[0]).newInstance());
                    } catch (Throwable var7) {
                        throw new ServletException("Failed to instantiate WebApplicationInitializer class", var7);
                    }
                }
            }
        }
...
}

public abstract class AbstractContextLoaderInitializer implements WebApplicationInitializer {
    protected final Log logger = LogFactory.getLog(this.getClass());
    public AbstractContextLoaderInitializer() {
    }
    public void onStartup(ServletContext servletContext) throws ServletException {
        this.registerContextLoaderListener(servletContext);
    }
    protected void registerContextLoaderListener(ServletContext servletContext) {
        WebApplicationContext rootAppContext = this.createRootApplicationContext();
        if (rootAppContext != null) {
            ContextLoaderListener listener = new ContextLoaderListener(rootAppContext);
            listener.setContextInitializers(this.getRootApplicationContextInitializers());
            servletContext.addListener(listener);
        } else {
            this.logger.debug("No ContextLoaderListener registered, as createRootApplicationContext() did not return an application context");
        }
    }

public abstract class AbstractDispatcherServletInitializer extends AbstractContextLoaderInitializer {
public static final String DEFAULT_SERVLET_NAME = "dispatcher";
public AbstractDispatcherServletInitializer() {
}
public void onStartup(ServletContext servletContext) throws ServletException {
    super.onStartup(servletContext);
    this.registerDispatcherServlet(servletContext);
}
protected void registerDispatcherServlet(ServletContext servletContext) {
    String servletName = this.getServletName();
    Assert.hasLength(servletName, "getServletName() must not return null or empty");
    // 可以看一下,它创建的是web的容器 
    WebApplicationContext servletAppContext = this.createServletApplicationContext();
    Assert.notNull(servletAppContext, "createServletApplicationContext() must not return null");
    // 创建负责调度的 DispatcherServlet
    FrameworkServlet dispatcherServlet = this.createDispatcherServlet(servletAppContext);
    Assert.notNull(dispatcherServlet, "createDispatcherServlet(WebApplicationContext) must not return null");
    dispatcherServlet.setContextInitializers(this.getServletApplicationContextInitializers());
    // 添加Servlet 
    Dynamic registration = servletContext.addServlet(servletName, dispatcherServlet);
    if (registration == null) {
        throw new IllegalStateException("Failed to register servlet with name '" + servletName + "'. Check if there is another servlet registered under the same name.");
    } else {
        // 添加servlet的mapping信息
        registration.setLoadOnStartup(1);
        registration.addMapping(this.getServletMappings());
        registration.setAsyncSupported(this.isAsyncSupported());
        Filter[] filters = this.getServletFilters();
        if (!ObjectUtils.isEmpty(filters)) {
            Filter[] var7 = filters;
            int var8 = filters.length;
            for(int var9 = 0; var9 < var8; ++var9) {
                Filter filter = var7[var9];
                this.registerServletFilter(servletContext, filter);
            }
        }
        this.customizeRegistration(registration);
    }
  ...
  }

public abstract class AbstractAnnotationConfigDispatcherServletInitializer extends AbstractDispatcherServletInitializer {
    public AbstractAnnotationConfigDispatcherServletInitializer() {
    }
    @Nullable
    protected WebApplicationContext createRootApplicationContext() {
        Class<?>[] configClasses = this.getRootConfigClasses();
        if (!ObjectUtils.isEmpty(configClasses)) {
            AnnotationConfigWebApplicationContext context = new 有没有大神了解这个情况, SpringMvc的应用上下文和Servlet应用上下文竟然是同一个();
            context.register(configClasses);
            return context;
        } else {
            return null;
        }
    }
    protected WebApplicationContext createServletApplicationContext() {
        AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
        Class<?>[] configClasses = this.getServletConfigClasses();
        if (!ObjectUtils.isEmpty(configClasses)) {
            context.register(configClasses);
        }
        return context;
    }

public class MyWebApplicationInitializer implements WebApplicationInitializer {
    @Override
    public void onStartup(ServletContext servletCxt) {
        // Load Spring web application configuration
        AnnotationConfigWebApplicationContext ac = new AnnotationConfigWebApplicationContext();
        ac.register(AppConfig.class);
        ac.refresh();
        // Create and register the DispatcherServlet
        DispatcherServlet servlet = new DispatcherServlet(ac);
        ServletRegistration.Dynamic registration = servletCxt.addServlet("app", servlet);
        registration.setLoadOnStartup(1);
        registration.addMapping("/app/*");
    }
}

public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    // 获取Spring容器的配置类
    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class[]{RootConfig.class};
    }
    // 获取web容器的配置类
    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{WebConfig.class};
    }
    /**
     * 获取DispatcherSerlvet的映射信息
     * / : 表示拦截所有请求(包含静态资源 XXX.js  XXX.jpg) 但是不包含 XXX.jsp
     * /* : 表示拦截所有请求(包含静态资源 XXX.js  XXX.jpg) 包含 XXX.jsp
     * @return
     */
    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }
}

@ComponentScan(value = "com.changwu",includeFilters = {
        @ComponentScan.Filter(type = FilterType.ANNOTATION,classes = {Controller.class})
},useDefaultFilters = false)
public class WebConfig {
}
@ComponentScan(value = "com.changwu",excludeFilters = {
        @ComponentScan.Filter(type = FilterType.ANNOTATION,classes = {Controller.class})
})
public class RootConfig {
}

// 启动异步
@WebServlet(value = "/async",asyncSupported = true)
public class MyAsyncServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 开启异步处理
        AsyncContext asyncContext = req.startAsync();
        asyncContext.start(new Runnable() {
            @Override
            public void run() {
                // do other things
                // 结束
                asyncContext.complete();
                // 响应
                ServletResponse response = asyncContext.getResponse();
                try {
                    response.getWriter().write("123");
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

@GetMapping("/quotes")
@ResponseBody
public DeferredResult<String> quotes() {
    DeferredResult<String> deferredResult = new DeferredResult<String>();
    // Save the deferredResult somewhere..
    return deferredResult;
}
// From some other thread...
deferredResult.setResult(result);

@PostMapping
public Callable<String> processUpload(final MultipartFile file) {
    return new Callable<String>() {
        public String call() throws Exception {
            // ...
            return "someView";
        }
    };
}

String getMethod()

String getContextPath()

String  getServletPath()

String getQueryString()

String getRequestURI()

String getRequestURL()

String getProtocol()

String getRemoteAddr()

String getHeader(String name);

Enumertion<String> getHeaderNames(); 获取所有请求头的名称

BufferReader getReader(); // 获取字符输入流
ServletInputStream getInputStrream(); // 获取字节输入流

String getParamter(String name); 根据参数名获取参数值

String [] getParameterValues(String name)

Enumeration<String> getParamerterNames()

Map<String,String[]) getParamerterMap()

request.setCharacterEncoding("utf-8")

RequestDispatcher getRequestDispacher(String path) // path是另一个Servlet的url-pattern
forward(currentReq,currentRes);

在AServlet
setAttribute(String name,Object obj);
请求转发到BServlet
在BServlet
getAttribute(String name);
移除
removeAttribute(String name);