5年网站seo优化公司,asp网站作业下载,甘肃省住房和建设厅网站服务中心,wordpress企业网站定制教程 一目录 前言一、场景二、原因分析三、解决四、更多 前言 曾经遇见这么一段代码#xff0c;能看出来是把request又重新包装了一下#xff0c;核心信息都不会改变
后面了解到这叫
装饰器模式#xff08;Decorator Pattern#xff09; #xff1a;也称为包装模式(Wrapper Pat… 目录 前言一、场景二、原因分析三、解决四、更多 前言 曾经遇见这么一段代码能看出来是把request又重新包装了一下核心信息都不会改变
后面了解到这叫
装饰器模式Decorator Pattern 也称为包装模式(Wrapper Pattern) 是指在不改变原有对象的基础之上将功能附加到对象上提供了比继承更有弹性的替代方案(扩展原有对象的功能)属于结构型模式。 装饰器模式的核心是功能扩展使用装饰器模式可以透明且动态地扩展类的功能。
概念是这样但还是不懂好好的你装饰它干啥
一、场景 最常见的场景在进入到控制器之前请求httpRequest在过滤器或拦截器中被处理
这些处理可能是 读取请求体RequestBody中的某个属性值 Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {// ....code ServletUtils.getRequestBodyValue(request,code);// ...}public static String getRequestBodyValue(HttpServletRequest request,String key) throws IOException, JSONException {if (key null || key.isEmpty()) {throw new IllegalArgumentException(Key cannot be null or empty.);}// 读取请求体BufferedReader reader new BufferedReader(new InputStreamReader(request.getInputStream()));String line;while ((line reader.readLine()) ! null) {requestBody.append(line);}// 解析JSON字符串JSONObject jsonObject JSON.parseObject(requestBody.toString());// 获取参数值String value jsonObject.getString(key);return value;}
当我这么做的时候发现在请求进入到Controller后报错了。
运行报错HttpMessageNotReadableException: Required request body is missing:
二、原因分析
过滤器中的 request.getInputStream读取了请求流的信息后续的过滤器或者Controller(RequestBody)都将得到一个“失效”的Request对象
展开讲讲
在Java的HttpServletRequest中请求体Request Body是以流的形式提供的通常通过getInputStream()或getReader()方法访问。这些方法只能被调用一次
为啥呢 请求体是一个输入流ServletInputStream流的内容是按顺序读取的。 流一旦被读取后指针会移动到流的末尾后续再次读取时将无法重新获取内容 其次HTTP协议本身设计为单次传输请求体流的内容在传输完成后不会自动重置。 gan没看懂反正就是只能读一次呗
三、解决
出来吧装饰器–
核心继承HttpServletRequestWrapper应用了装饰器模式对HttpServletRequest进行了增强。 具体表现为缓存请求体并且重写getInputStream和getReader方法。
一句话 后续读取的是缓存的请求体而不是原始流
package com.hong.security.common;import org.springframework.util.StreamUtils;import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;/*** author wanghong* date 2020/05/11 22:47**/
public class WrappedRequest extends HttpServletRequestWrapper {private byte[] requestBody null;public WrappedRequest(HttpServletRequest request) {super(request);// 缓存请求bodytry {requestBody StreamUtils.copyToByteArray(request.getInputStream());} catch (IOException e) {e.printStackTrace();}}Overridepublic ServletInputStream getInputStream() throws IOException {if (requestBody null) {requestBody new byte[0];}final ByteArrayInputStream bais new ByteArrayInputStream(requestBody);return new ServletInputStream() {Overridepublic int read() throws IOException {return bais.read();}Overridepublic boolean isFinished() {// TODO Auto-generated method stubreturn true;}Overridepublic boolean isReady() {// TODO Auto-generated method stubreturn true;}Overridepublic void setReadListener(ReadListener listener) {// TODO Auto-generated method stub}};}Overridepublic BufferedReader getReader() throws IOException {return new BufferedReader(new InputStreamReader(getInputStream()));}
} 如果在构造MyRequestBodyWrapper之前已经有其他组件读取了请求体则会导致缓存失败。因此确保这个包装器是在请求体首次读取之前应用的非常重要 import com.tty.tty_admin.common.entity.MyRequestBodyWrapper;
import org.springframework.stereotype.Component;
import org.springframework.util.ServletUtils;import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;Component // 必须注册到容器中才能生效
public class MyTestFilter implements Filter {Overridepublic void init(FilterConfig filterConfig) throws ServletException {Filter.super.init(filterConfig);}Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println(我的测试);HttpServletRequest request (HttpServletRequest) servletRequest;MyRequestBodyWrapper wrappedRequest new MyRequestBodyWrapper(request);// 获取请求体内容可选String code ServletUtils.getRequestBodyValue(request, code);System.out.println(code);// 传递装饰后的请求对象filterChain.doFilter(wrappedRequest, servletResponse);}Overridepublic void destroy() {Filter.super.destroy();}filterChain.doFilter(wrappedRequest, servletResponse); 这样就能保证传入控制器的是requestwrapper而不是原request
四、更多
学习若依框架发现利用Spring Cloud Gateway内置的ServerWebExchangeUtils.cacheRequestBodyAndRequest方法减少了手动实现请求包装器的复杂性
CacheRequestFilter优秀优秀
package com.ruoyi.gateway.filter;import java.util.Collections;
import java.util.List;
import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.OrderedGatewayFilter;
import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
import org.springframework.cloud.gateway.support.ServerWebExchangeUtils;
import org.springframework.http.HttpMethod;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;/*** 解决流不能重复读取问题* * author ruoyi*/
Component
public class CacheRequestFilter extends AbstractGatewayFilterFactoryCacheRequestFilter.Config
{public CacheRequestFilter(){super(Config.class);}Overridepublic String name(){return CacheRequestFilter;}Overridepublic GatewayFilter apply(Config config){CacheRequestGatewayFilter cacheRequestGatewayFilter new CacheRequestGatewayFilter();Integer order config.getOrder();if (order null){return cacheRequestGatewayFilter;}return new OrderedGatewayFilter(cacheRequestGatewayFilter, order);}public static class CacheRequestGatewayFilter implements GatewayFilter{Overridepublic MonoVoid filter(ServerWebExchange exchange, GatewayFilterChain chain){// GET DELETE 不过滤get请求没有请求体delete请求一般也不会用到HttpMethod method exchange.getRequest().getMethod();if (method null || method HttpMethod.GET || method HttpMethod.DELETE){return chain.filter(exchange);}return ServerWebExchangeUtils.cacheRequestBodyAndRequest(exchange, (serverHttpRequest) - {if (serverHttpRequest exchange.getRequest()){return chain.filter(exchange);}return chain.filter(exchange.mutate().request(serverHttpRequest).build());});}}Overridepublic ListString shortcutFieldOrder(){return Collections.singletonList(order);}static class Config{private Integer order;public Integer getOrder(){return order;}public void setOrder(Integer order){this.order order;}}
}重点这一段
return ServerWebExchangeUtils.cacheRequestBodyAndRequest(exchange, (serverHttpRequest) - {if (serverHttpRequest exchange.getRequest()){return chain.filter(exchange);}return chain.filter(exchange.mutate().request(serverHttpRequest).build());});使用装饰器后控制器中会自动使用装饰后的ServerWebExchange中的request对象这是因为Spring Cloud Gateway在处理请求时会通过过滤器链来修改和增强ServerWebExchange。具体来说CacheRequestFilter通过ServerWebExchangeUtils.cacheRequestBodyAndRequest方法缓存了请求体并替换了原始的ServerWebExchange中的请求对象。
