I use nginx proxy tomcat, but there have been many 400 error, about 10%.
But do not use nginx, tomcat can normally handle this part of the request.
This is my nginx configuration :
user nobody;
worker_processes 1;

error_log logs/error.log;
pid logs/nginx.pid;

events {
# use [ kqueue | rtsig | epoll | /dev/poll | select | poll ];
use epoll;

# web server : max_clients = worker_processes * worker_connections
# proxy server : max_clients = worker_processes * worker_connections / 4
worker_connections 8192;
}

http {
include mime.types;
default_type application/octet-stream;

log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for" |body: $request_body' ' $request_time' ' $host';

#access_log logs/access.log main;

sendfile on;
tcp_nopush on;

keepalive_timeout 90;

gzip on;
gzip_comp_level 5;
gzip_http_version 1.0;
gzip_min_length 1024;
gzip_buffers 4 8k;
gzip_types text/plain application/x-javascript text/css application/xml;

client_header_buffer_size 32k;
large_client_header_buffers 4 32k;
#client_max_body_size 2M;
#client_body_buffer_size 512k;
fastcgi_intercept_errors on;
fastcgi_connect_timeout 300;
fastcgi_send_timeout 300;
fastcgi_read_timeout 300;
fastcgi_buffers 4 256k;
fastcgi_busy_buffers_size 256k;
fastcgi_buffer_size 128k;
proxy_ignore_client_abort on;

#proxy_buffer_size 32k;
#proxy_buffers 4 32k;
# The following includes are specified for virtual hosts
include vhosts/*.conf;
}

upstream download {
server 127.0.0.1:8001 weight=1;
}

server {
listen 80;
server_name 210.209.116.176 *.newlife-sh.com;
access_log logs/download.log main;
location /{
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header REMOTE-HOST $remote_addr;
# proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
client_max_body_size 50m;
client_body_buffer_size 1024k;
proxy_intercept_errors on;
error_page 400 error;
proxy_connect_timeout 90;
proxy_send_timeout 120;
proxy_read_timeout 300;
proxy_buffer_size 4m;
proxy_buffers 8 1024k;
proxy_busy_buffers_size 4m;
proxy_temp_file_write_size 16m;
proxy_next_upstream error timeout invalid_header http_500 http_503 http_404;
proxy_max_temp_file_size 128m;
proxy_pass http://download;
}
location /nginxstatus {
access_log on;
allow all;
}
}