HttpSevletRequest Body信息多次读取填坑录-java

1、背景

业务拦截器需要拦截request的所有传入信息。通常情况下,HttpServletRequst 中的 body 内容只会读取一次,但是可能某些情境下可能会读取多次,由于 body 内容是以流的形式存在,所以第一次读取完成后,第二次就无法读取了,一个典型的场景就是 Filter 在校验完成 body 的内容后,业务方法就无法继续读取流了,导致解析报错。

2、解决方案

我们是否可以用装饰器来修饰一下 request,使其可以包装读取的内容,供多次读取。

这个装饰器要符合httpsevletrequest接口规范，在原有的框架中spring boot提供了一个简单的封装器ContentCachingRequestWrapper，从源码上看这个封装器并不实用，没有封装http的底层流ServletInputStream信息，导致使用@RequestParam,@RequestBody等使用底层流构建的逻辑依然无用，只能硬生生的使用

  public byte[] getContentAsByteArray() {
   return this.cachedContent.toByteArray();
}
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来自己在业务中处理body信息。 这里，我参照ContentCachingRequestWrapper封装了一个更具可靠性，更低侵入性的装饰器：

  package com.interceptor;

import org.apache.commons.collections.CollectionUtils;
import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.lang.Nullable;
import org.springframework.web.util.WebUtils;

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.*;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

/**
 * @author sean
 */
public class RepeatReadHttpRequest extends HttpServletRequestWrapper {
    private static final Logger LOGGER = LoggerFactory.getLogger(RepeatReadHttpRequest.class);
    private final ByteArrayOutputStream cachedContent;
    private Map cachedForm;

    @Nullable
    private ServletInputStream inputStream;

    public RepeatReadHttpRequest(HttpServletRequest request) {
        super(request);
        this.cachedContent = new ByteArrayOutputStream();
        this.cachedForm = new HashMap<>();
        cacheData();
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        this.inputStream = new RepeatReadInputStream(cachedContent.toByteArray());
        return this.inputStream;
    }

    @Override
    public String getCharacterEncoding() {
        String enc = super.getCharacterEncoding();
        return (enc != null ? enc : WebUtils.DEFAULT_CHARACTER_ENCODING);
    }

    @Override
    public BufferedReader getReader() throws IOException {
         return new BufferedReader(new InputStreamReader(getInputStream(), getCharacterEncoding()));
    }

    @Override
    public String getParameter(String name) {
        String value = null;
        if (isFormPost()) {
            String[] values = cachedForm.get(name);
            if (null != values && values.length > 0) {
                value = values[0];
            }
        }

        if (StringUtils.isEmpty(value)) {
            value = super.getParameter(name);
        }

        return value;
    }

    @Override
    public Map getParameterMap() {
        if (isFormPost() && !CollectionUtils.sizeIsEmpty(cachedForm)) {
            return cachedForm;
        }

        return super.getParameterMap();
    }

    @Override
    public Enumeration getParameterNames() {
        if (isFormPost() && !CollectionUtils.sizeIsEmpty(cachedForm)) {
            return Collections.enumeration(cachedForm.keySet());
        }

        return super.getParameterNames();
    }

    @Override
    public String[] getParameterValues(String name) {
        if (isFormPost() && !CollectionUtils.sizeIsEmpty(cachedForm)) {
            return cachedForm.get(name);
        }

        return super.getParameterValues(name);
    }

    private void cacheData() {
        try {
            if (isFormPost()) {
                this.cachedForm = super.getParameterMap();
            } else {
                ServletInputStream inputStream = super.getInputStream();
                IOUtils.copy(inputStream, this.cachedContent);
            }
        } catch (IOException e) {
            LOGGER.warn("[RepeatReadHttpRequest:cacheData], error: {}", e.getMessage());
        }

    }

    private boolean isFormPost() {
        String contentType = getContentType();
        return (contentType != null &&
                (contentType.contains(MediaType.APPLICATION_FORM_URLENCODED_VALUE) ||
                        contentType.contains(MediaType.MULTIPART_FORM_DATA_VALUE)) &&
                HttpMethod.POST.matches(getMethod()));
    }

    private static class RepeatReadInputStream extends ServletInputStream {
        private final ByteArrayInputStream inputStream;

        public RepeatReadInputStream(byte[] bytes) {
            this.inputStream = new ByteArrayInputStream(bytes);
        }

        @Override
        public int read() throws IOException {
            return this.inputStream.read();
        }

        @Override
        public int readLine(byte[] b, int off, int len) throws IOException {
            return this.inputStream.read(b, off, len);
        }

        @Override
        public boolean isFinished() {
            return this.inputStream.available() == 0;
        }

        @Override
        public boolean isReady() {
            return true;
        }

        @Override
        public void setReadListener(ReadListener listener) {

        }
    }
}
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使用这个装饰器时需要配合Filter对原有的request进行偷梁换柱，注册Filter并在调用链中将原有的request换成

  RepeatReadHttpRequest
package com.interceptor;

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.util.ContentCachingRequestWrapper;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

/**
 * @author sean
 * 拦截器httprequest替换 可重复获取inputstream
 */
@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean requestReplaceFilterRegistration() {
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        registrationBean.setFilter(new RequestReplaceFilter());
        registrationBean.addUrlPatterns("/*");
        registrationBean.setName("RequestReplaceFilter");
        registrationBean.setOrder(1);
        return registrationBean;
    }

    public static class RequestReplaceFilter implements Filter {
        @Override
        public void init(javax.servlet.FilterConfig filterConfig) throws ServletException {

        }

        @Override
        public void destroy() {

        }

        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            filterChain.doFilter(new RepeatReadHttpRequest((HttpServletRequest) servletRequest), servletResponse);
        }
    }
}
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后续的request就可以使用封装器多次读取body信息。