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Springboot2拦截器与文件上传

2021-07-21 19:34:41  阅读：201  来源： 互联网

标签：... 拦截器 return request public Springboot2 null 上传 response


拦截器-登录检查与静态资源放行

1.编写一个拦截器实现HandlerInterceptor接口

2.拦截器注册到容器中（实现WebMvcConfigurer的addInterceptors()）

3.指定拦截规则（注意，如果是拦截所有，静态资源也会被拦截】

还是以上一节Springboot视图解析与模板引擎为例，访问除登录页面外的其它任何请求，都应该是登录之后才能访问的。我们可以使用拦截器对请求进行拦截，从而进行相应的处理。

public interface HandlerInterceptor {
    default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        return true;
    }

    default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {
    }

    default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {
    }
}

拦截器必须要实现HandlerInterceptor 接口
HandlerInterceptor 定义了3个方法，preHandle预先处理，即目标方法处理之前进行处理。目标方法处理完之后，但是还没有到达指定页面之前，我们需要给页面再放一些数据，可以用postHandle进行后置拦截。在请求处理完成之后要做的工作用afterCompletion来处理。
在这里插入图片描述
编写一个实现HandlerInterceptor接口的拦截器：

/*
登录检查
1.配置好拦截器要拦截哪些请求
2.把这些配置放在容器中(实现WebConfigurer的addUbtercepter）
3.指定拦截规则（如果是拦截所有，静态资源也会被拦截）
* */
public class LoginIntercepter implements HandlerInterceptor {
    /*
    * 目标方法执行之前
    * */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //登录检查逻辑
        HttpSession session=request.getSession();
        Object loginUser =session.getAttribute("loginUser");
        if(loginUser!=null){
            //放行
            return true;
        }
        //拦截住,未登录，跳转到登录页
//        session.setAttribute("msg","请先登录");
//        response.sendRedirect("/");

        request.setAttribute("msg","请先登录");
        //如果是重定向取不出来错误消息
        request.getRequestDispatcher("/").forward(request,response);
        return false;
    }
    /*
    * 目标方法执行完成之后
    * */
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }
    /*
    * 页面渲染以后
    * */
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

    }
}

拦截器注册到容器中 && 指定拦截规则：

@Configuration
public class AdminWebConfig implements WebMvcConfigurer{
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginIntercepter())
                // /**会拦截所有请求，包括静态资源
                .addPathPatterns("/**")             //拦截哪些
                .excludePathPatterns("/","/login","/css/**","/js/**","/fonts/**","/images/**");  //放行哪些
    }
}

注意：这里使用/的时候会拦截掉所有资源，包括静态资源，因此需要对静态资源进行放行，我们静态资源都是保存在static目录下， 而这里不能直接对/static/，因为访问静态资源的时候url不会写static。

拦截器-【源码分析】-拦截器的执行时机和原理

1.根据当前请求，找到HandlerExecutionChain（可以处理请求的handler以及handler的所有 拦截器）
2.先来顺序执行 所有拦截器的 preHandle()方法。

  1. 如果当前拦截器preHandle()返回为true。则执行下一个拦截器的preHandle()
  2. 如果当前拦截器返回为false。直接倒序执行所有已经执行了的拦截器的 afterCompletion();。

3.如果任何一个拦截器返回false，直接跳出不执行目标方法。
4.所有拦截器都返回true，才执行目标方法。
5.倒序执行所有拦截器的postHandle()方法。
6.前面的步骤有任何异常都会直接倒序触发 afterCompletion()。
7.页面成功渲染完成以后，也会倒序触发 afterCompletion()。

在这里插入图片描述

public class DispatcherServlet extends FrameworkServlet {
    
    ...
    
	protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HttpServletRequest processedRequest = request;
		HandlerExecutionChain mappedHandler = null;
		boolean multipartRequestParsed = false;

		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

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

            	...
            
                //该方法内调用HandlerInterceptor的preHandle()
				if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					return;
				}

				// Actually invoke the handler.
				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

            	...
                //该方法内调用HandlerInterceptor的postHandle()
				mappedHandler.applyPostHandle(processedRequest, response, mv);
			}			
        	processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
		}
		catch (Exception ex) {
            //该方法内调用HandlerInterceptor接口的afterCompletion方法
			triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
		}
		catch (Throwable err) {
            //该方法内调用HandlerInterceptor接口的afterCompletion方法
			triggerAfterCompletion(processedRequest, response, mappedHandler,
					new NestedServletException("Handler processing failed", err));
		}
		finally {
			...
		}
	}

	private void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response,
			@Nullable HandlerExecutionChain mappedHandler, Exception ex) throws Exception {

		if (mappedHandler != null) {
            //该方法内调用HandlerInterceptor接口的afterCompletion方法
			mappedHandler.triggerAfterCompletion(request, response, ex);
		}
		throw ex;
	}

	private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
			@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
			@Nullable Exception exception) throws Exception {

        ...

		if (mappedHandler != null) {
            //该方法内调用HandlerInterceptor接口的afterCompletion方法
			// Exception (if any) is already handled..
			mappedHandler.triggerAfterCompletion(request, response, null);
		}
	}


}

public class HandlerExecutionChain {
    
    ...
    
	boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
		for (int i = 0; i < this.interceptorList.size(); i++) {
			HandlerInterceptor interceptor = this.interceptorList.get(i);
            //HandlerInterceptor的preHandle方法
			if (!interceptor.preHandle(request, response, this.handler)) {
                
				triggerAfterCompletion(request, response, null);
				return false;
			}
			this.interceptorIndex = i;
		}
		return true;
	}
    
   	void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)
			throws Exception {

		for (int i = this.interceptorList.size() - 1; i >= 0; i--) {
			HandlerInterceptor interceptor = this.interceptorList.get(i);
            
            //HandlerInterceptor接口的postHandle方法
			interceptor.postHandle(request, response, this.handler, mv);
		}
	}
    
    void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex) {
		for (int i = this.interceptorIndex; i >= 0; i--) {
			HandlerInterceptor interceptor = this.interceptorList.get(i);
			try {
                //HandlerInterceptor接口的afterCompletion方法
				interceptor.afterCompletion(request, response, this.handler, ex);
			}
			catch (Throwable ex2) {
				logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
			}
		}
	}
    
    
}

文件上传-单文件上传与多文件上传

使用form_layouts.html文件来实现文件上传。

在common.html中修改form_layouts的请求发送，即当在main.html中点击Form Layouts能够响应form_layouts请求。

<li class="menu-list"><a href=""><i class="fa fa-tasks"></i> <span>Forms</span></a>
                <ul class="sub-menu-list">
                    <li><a th:href="@{/form_layouts}"> Form Layouts</a></li>
                    <li><a href="form_advanced_components.html"> Advanced Components</a>

在FormTestController处理文件上传的请求

/*
* 文件上传测试
* */
@Slf4j
@Controller
public class FormTestController {
    @GetMapping("/form_layouts")
    public String form_layouts(){
        return "form/form_layouts";
    }
    //因为使用post方式提交
    //该函数的作用是可以自动封装上传过来的文件
    @PostMapping("/upload")
    /*
    * @RequestParam代表从请求参数中取值
    * 取出表单中的文件项用@RequestPart注解，文件用MultipartFile对象来存储
    * */
    public String upload(@RequestParam("email") String email,
                         @RequestParam("username") String username,
                         @RequestPart("headerImg") MultipartFile headerImg,
                         @RequestPart("photos") MultipartFile[] photos) throws IOException {
        log.info("上传的信息：email={}，username={}，headerImg={}，photos={}",
                email,username,headerImg.getSize(),photos.length);
        System.out.println(email+" "+username+" "+headerImg.getSize()+" "+photos.length);
        if(!headerImg.isEmpty()){
            //保存到文件服务器，OSS文件服务器
            String originalFilename = headerImg.getOriginalFilename();
            headerImg.transferTo(new File("D:\\bootimg\\"+originalFilename));
        }
        if(photos.length>0){
            for(MultipartFile photo:photos){
                if(!photo.isEmpty()){
                    String originalFilename = photo.getOriginalFilename();
                    photo.transferTo(new File("D:\\bootimg\\"+originalFilename));

                }
            }
        }
        return "main";
    }
}

form_layouts.html文件中文件上传表单的信息

<form role="form" th:action="@{/upload}" method="post" enctype="multipart/form-data">
                            <div class="form-group">
                                <label for="exampleInputEmail1">邮箱</label>
                                <input type="email" name="email" class="form-control" id="exampleInputEmail1" placeholder="Enter email">
                            </div>
                            <div class="form-group">
                                <label for="exampleInputPassword1">名字</label>
                                <input type="text" name="username" class="form-control" id="exampleInputPassword1" placeholder="Password">
                            </div>
                            <div class="form-group">
                                <label for="exampleInputFile">头像</label>
                                <input type="file" name="headerImg" id="exampleInputFile">
                                <p class="help-block">Example block-level help text here.</p>
                            </div>
                            <div class="form-group">
                                <label for="exampleInputFile">生活照</label>
                                <!--multiple多文件上传-->
                                <input type="file" name="photos" multiple>
                                <p class="help-block">Example block-level help text here.</p>
                            </div>
                            <div class="checkbox">
                                <label>
                                    <input type="checkbox"> Check me out
                                </label>
                            </div>
                            <button type="submit" class="btn btn-primary">提交</button>
                        </form>

可以在application.properties中设置文件上传的参数

# 单个文件的最大大小
spring.servlet.multipart.max-file-size=10MB
# 整个请求的最大文件大小
spring.servlet.multipart.max-request-size=100MB

文件上传相关的配置类：

org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration
org.springframework.boot.autoconfigure.web.servlet.MultipartProperties

文件上传源码流程

文件上传自动配置类MultipartAutoConfiguration-MultipartProperties
自动配置好了StandardServletMultipartResolver [文件.上传解析器]
原理步骤
1.请求进来使用文件上传解析器判断(isMultipart) 并封装(resolveMultipart, 返回MultipartHttpServletRequest)文件.上传请求
2.参数解析器来解析请求中的文件内容封装成MultipartFile
3.将request中文件信息封装为-个Map; MultiValueMap< String, MultipartFile>
FileCopyUtils。实现文件流的拷贝

@PostMapping("/upload")
public String upload(@RequestParam("email") String email,
                     @RequestParam("username") String username,
                     @RequestPart("headerImg") MultipartFile headerImg,
                     @RequestPart("photos") MultipartFile[] photos)

文件上传相关的自动配置类MultipartAutoConfiguration有创建文件上传参数解析器StandardServletMultipartResolver。

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ Servlet.class, StandardServletMultipartResolver.class, MultipartConfigElement.class })
@ConditionalOnProperty(prefix = "spring.servlet.multipart", name = "enabled", matchIfMissing = true)
@ConditionalOnWebApplication(type = Type.SERVLET)
@EnableConfigurationProperties(MultipartProperties.class)
public class MultipartAutoConfiguration {

	private final MultipartProperties multipartProperties;

	public MultipartAutoConfiguration(MultipartProperties multipartProperties) {
		this.multipartProperties = multipartProperties;
	}

	@Bean
	@ConditionalOnMissingBean({ MultipartConfigElement.class, CommonsMultipartResolver.class })
	public MultipartConfigElement multipartConfigElement() {
		return this.multipartProperties.createMultipartConfig();
	}

	@Bean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME)
	@ConditionalOnMissingBean(MultipartResolver.class)
	public StandardServletMultipartResolver multipartResolver() {
        //配置好文件上传解析器
		StandardServletMultipartResolver multipartResolver = new StandardServletMultipartResolver();
		multipartResolver.setResolveLazily(this.multipartProperties.isResolveLazily());
		return multipartResolver;
	}

}

//文件上传解析器
public class StandardServletMultipartResolver implements MultipartResolver {

	private boolean resolveLazily = false;

	public void setResolveLazily(boolean resolveLazily) {
		this.resolveLazily = resolveLazily;
	}


	@Override
	public boolean isMultipart(HttpServletRequest request) {
		return StringUtils.startsWithIgnoreCase(request.getContentType(), "multipart/");
	}

	@Override
	public MultipartHttpServletRequest resolveMultipart(HttpServletRequest request) throws MultipartException {
		return new StandardMultipartHttpServletRequest(request, this.resolveLazily);
	}

	@Override
	public void cleanupMultipart(MultipartHttpServletRequest request) {
		if (!(request instanceof AbstractMultipartHttpServletRequest) ||
				((AbstractMultipartHttpServletRequest) request).isResolved()) {
			// To be on the safe side: explicitly delete the parts,
			// but only actual file parts (for Resin compatibility)
			try {
				for (Part part : request.getParts()) {
					if (request.getFile(part.getName()) != null) {
						part.delete();
					}
				}
			}
			catch (Throwable ex) {
				LogFactory.getLog(getClass()).warn("Failed to perform cleanup of multipart items", ex);
			}
		}
	}

}

public class DispatcherServlet extends FrameworkServlet {
    
    @Nullable
	private MultipartResolver multipartResolver;
    
	private void initMultipartResolver(ApplicationContext context) {
		...
        
        //这个就是配置类配置的StandardServletMultipartResolver文件上传解析器
		this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class);
		...
	}
    
	protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HttpServletRequest processedRequest = request;
		HandlerExecutionChain mappedHandler = null;
		boolean multipartRequestParsed = false;//最后finally的回收flag
		...
		try {
			ModelAndView mv = null;
			Exception dispatchException = null;

			try {
                //做预处理,如果有上传文件 就new StandardMultipartHttpServletRequest包装类
				processedRequest = checkMultipart(request);
				multipartRequestParsed = (processedRequest != request);
				// Determine handler for the current request.
				mappedHandler = getHandler(processedRequest);
				
                ...

				// Determine handler adapter for the current request.
				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

				...

				// Actually invoke the handler.
				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
                
            }
            ....
            
		finally {

            ...
            
            if (multipartRequestParsed) {
                cleanupMultipart(processedRequest);
            }
		}
	}

	protected HttpServletRequest checkMultipart(HttpServletRequest request) throws MultipartException {
		if (this.multipartResolver != null && this.multipartResolver.isMultipart(request)) {
            ...
			return this.multipartResolver.resolveMultipart(request);
            ...
		}
    }

	protected void cleanupMultipart(HttpServletRequest request) {
		if (this.multipartResolver != null) {
			MultipartHttpServletRequest multipartRequest =
					WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class);
			if (multipartRequest != null) {
				this.multipartResolver.cleanupMultipart(multipartRequest);
			}
		}
	}
}

mv = ha.handle(processedRequest, response, mappedHandler.getHandler());跳到以下的类

public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
		implements BeanFactoryAware, InitializingBean {
	@Override
	protected ModelAndView handleInternal(HttpServletRequest request,
			HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
		ModelAndView mav;
		...
		mav = invokeHandlerMethod(request, response, handlerMethod);
        ...
		return mav;
	}
    
    @Nullable
	protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
			HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {

		ServletWebRequest webRequest = new ServletWebRequest(request, response);
		try {
			WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
			ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);

			ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
			if (this.argumentResolvers != null) {//关注点
				invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
			}
			...
			invocableMethod.invokeAndHandle(webRequest, mavContainer);
			...

			return getModelAndView(mavContainer, modelFactory, webRequest);
		}
		finally {
			webRequest.requestCompleted();
		}
	}
    
}

this.argumentResolvers其中主角类RequestPartMethodArgumentResolver用来生成

public class ServletInvocableHandlerMethod extends InvocableHandlerMethod {
    
    ...
	public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {
		Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
		...
	}
    
	@Nullable
	public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {

		Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
		...
		return doInvoke(args);//反射调用
	}
    
	@Nullable
	protected Object doInvoke(Object... args) throws Exception {
		Method method = getBridgedMethod();
		ReflectionUtils.makeAccessible(method);
		return method.invoke(getBean(), args);
		...
	}
    
    //处理得出multipart参数，准备稍后的反射调用（@PostMapping标记的上传方法）
    protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {

		MethodParameter[] parameters = getMethodParameters();
		...
		Object[] args = new Object[parameters.length];
		for (int i = 0; i < parameters.length; i++) {
			MethodParameter parameter = parameters[i];
			parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
			args[i] = findProvidedArgument(parameter, providedArgs);
			if (args[i] != null) {
				continue;
			}
            //关注点1
			if (!this.resolvers.supportsParameter(parameter)) {
				throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
			}
			try {
                //关注点2
				args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
			}
			catch (Exception ex) {
				...
			}
		}
		return args;
	}
    
}

public class RequestPartMethodArgumentResolver extends AbstractMessageConverterMethodArgumentResolver {

    //对应上面代码关注点1
    @Override
	public boolean supportsParameter(MethodParameter parameter) {
        //标注@RequestPart的参数
		if (parameter.hasParameterAnnotation(RequestPart.class)) {
			return true;
		}
		else {
			if (parameter.hasParameterAnnotation(RequestParam.class)) {
				return false;
			}
			return MultipartResolutionDelegate.isMultipartArgument(parameter.nestedIfOptional());
		}
	}

    //对应上面代码关注点2
	@Override
	@Nullable
	public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest request, @Nullable WebDataBinderFactory binderFactory) throws Exception {

		HttpServletRequest servletRequest = request.getNativeRequest(HttpServletRequest.class);
		Assert.state(servletRequest != null, "No HttpServletRequest");

		RequestPart requestPart = parameter.getParameterAnnotation(RequestPart.class);
		boolean isRequired = ((requestPart == null || requestPart.required()) && !parameter.isOptional());

		String name = getPartName(parameter, requestPart);
		parameter = parameter.nestedIfOptional();
		Object arg = null;

        //封装成MultipartFile类型的对象作参数
		Object mpArg = MultipartResolutionDelegate.resolveMultipartArgument(name, parameter, servletRequest);
		if (mpArg != MultipartResolutionDelegate.UNRESOLVABLE) {
			arg = mpArg;
		}
        
        ...

		return adaptArgumentIfNecessary(arg, parameter);
	}
}

public final class MultipartResolutionDelegate {
    ...
    
	@Nullable
	public static Object resolveMultipartArgument(String name, MethodParameter parameter, HttpServletRequest request)
			throws Exception {

		MultipartHttpServletRequest multipartRequest =
				WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class);
		boolean isMultipart = (multipartRequest != null || isMultipartContent(request));

		if (MultipartFile.class == parameter.getNestedParameterType()) {
			if (!isMultipart) {
				return null;
			}
			if (multipartRequest == null) {
				multipartRequest = new StandardMultipartHttpServletRequest(request);
			}
			return multipartRequest.getFile(name);
		}
		else if (isMultipartFileCollection(parameter)) {
			if (!isMultipart) {
				return null;
			}
			if (multipartRequest == null) {
				multipartRequest = new StandardMultipartHttpServletRequest(request);
			}
			List<MultipartFile> files = multipartRequest.getFiles(name);
			return (!files.isEmpty() ? files : null);
		}
		else if (isMultipartFileArray(parameter)) {
			if (!isMultipart) {
				return null;
			}
			if (multipartRequest == null) {
				multipartRequest = new StandardMultipartHttpServletRequest(request);
			}
			List<MultipartFile> files = multipartRequest.getFiles(name);
			return (!files.isEmpty() ? files.toArray(new MultipartFile[0]) : null);
		}
		else if (Part.class == parameter.getNestedParameterType()) {
			if (!isMultipart) {
				return null;
			}
			return request.getPart(name);
		}
		else if (isPartCollection(parameter)) {
			if (!isMultipart) {
				return null;
			}
			List<Part> parts = resolvePartList(request, name);
			return (!parts.isEmpty() ? parts : null);
		}
		else if (isPartArray(parameter)) {
			if (!isMultipart) {
				return null;
			}
			List<Part> parts = resolvePartList(request, name);
			return (!parts.isEmpty() ? parts.toArray(new Part[0]) : null);
		}
		else {
			return UNRESOLVABLE;
		}
	}
    
    ...
    
}

标签：...,拦截器,return,request,public,Springboot2,null,上传,response
来源： https://blog.csdn.net/qq_39736597/article/details/118959609

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