Transfer-Encoding: chunked添加Content-Length: 574712返回

一、问题背景：

开发中有时候有的功能需要返回content-length字段，根据此字段进行下载进度的展示。而springboot默认在数据量大的时候是进行了Transfer-Encoding: chunked 设置的。
需要我们手动对需要返回Content-Length: 574712的接口进行filter配置。

二、添加filters

FilterConfig.java

package com.eduer.books.config;
 
import com.eduer.books.modules.app.filters.AddContentLengthFilter;
import com.google.common.collect.Lists;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration; 
 
import java.util.List;

/**
 * Filter配置
 *
 * @author books
 */
@Configuration
public class FilterConfig {

    /**
     * 给特定接口加content-length返回
     * @return FilterRegistrationBean
     */
    @Bean
    public FilterRegistrationBean contentLengthFilterRegistrationBean() {
        FilterRegistrationBean filterBean = new FilterRegistrationBean();
        filterBean.setFilter(new AddContentLengthFilter());
        List<String> urls = Lists.newArrayList();
        // 只针对指定接口类型返回content-length
        urls.add("/app/clientApi");
        filterBean.setUrlPatterns(urls);
        return filterBean;
    }
}

三、新建AddContentLengthFilter

AddContentLengthFilter.java

package com.eduer.books.modules.app.filters;

import org.springframework.web.filter.OncePerRequestFilter;
import org.springframework.web.util.ContentCachingResponseWrapper;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class AddContentLengthFilter extends OncePerRequestFilter {

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {

        ContentCachingResponseWrapper cacheResponseWrapper;
        if (!(response instanceof ContentCachingResponseWrapper)) {
            cacheResponseWrapper = new ContentCachingResponseWrapper(response);
        } else {
            cacheResponseWrapper = (ContentCachingResponseWrapper) response;
        }

        filterChain.doFilter(request, cacheResponseWrapper);

        cacheResponseWrapper.copyBodyToResponse();
    }
}

四、测试：

4.1 修改前：

Response Headers没有返回 Content-Length: 574712的属性。

4.2 修改后：

已经成功添加了 Content-Length: 574712的属性。

END