nginx 301 重定项跳转

将不带www的域名访问,跳转到带www的域名,实现nginx的301重定向               
 server_name www.simapple.com simapple.com;
 if ($host != 'www.simapple.com' ) {
              rewrite ^/(.*)$ http://www.simapple.com/$1 permanent;
 }