httpc 请求：错误的参数异常长度

Question

我在向 Java servlet 发出 httpc 请求时遇到问题。在我的本地系统上，代码运行良好，但如果我从 ejabberd 服务器的 erlang 文件执行调用，我会收到错误参数异常。

这是我本地系统的代码：

Body = "deviceToken=dy....[Very long FCM token]....b1&sender=epeued7o3z", inets:start(), httpc:request(post, { "http://192.168.2.110:8080/020/service", [], "application/x-www-form-urlencoded", Body }, [], []).

我将代码复制到 ejabberd 服务器的 erlang 文件中，但出现此异常：

2017-11-24 18:05:40 =CRASH REPORT==== crasher: initial call: httpc_handler:init/1 pid: <0.522.0> registered_name: [] exception error: bad argument: [{erlang,length,[[100,101,118,105,99,101,84,111,107,101,110,61,<<"dy....[Very long FCM token]...Kn4b1">>,38,115,101,110,100,101,114,61|<<"epeued7o3z">>]],[]},{httpc_request,body_length,1,[{file,"httpc_request.erl"},{line,233}]},{httpc_request,post_data,4,[{file,"httpc_request.erl"},{line,208}]},{httpc_request,send,4,[{file,"httpc_request.erl"},{line,85}]},{httpc_handler,connect_and_send_first_request,3,[{file,"httpc_handler.erl"},{line,815}]},{httpc_handler,init,1,[{file,"httpc_handler.erl"},{line,238}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,247}]}] ancestors: [httpc_handler_sup,httpc_sup,inets_sup,<0.439.0>] message_queue_len: 0 messages: [] links: [<0.445.0>,#Port<0.14269>] dictionary: [] trap_exit: true status: running heap_size: 610 stack_size: 27 reductions: 978 neighbours: 2017-11-24 18:05:40 =SUPERVISOR REPORT==== Supervisor: {local,httpc_handler_sup} Context: child_terminated Reason: {badarg,[{erlang,length,[[100,101,118,105,99,101,84,111,107,101,110,61,<<"dy...[Very long FCM token].....Kn4b1">>,38,115,101,110,100,101,114,61|<<"epeued7o3z">>]],[]},{httpc_request,body_length,1,[{file,"httpc_request.erl"},{line,233}]},{httpc_request,post_data,4,[{file,"httpc_request.erl"},{line,208}]},{httpc_request,send,4,[{file,"httpc_request.erl"},{line,85}]},{httpc_handler,connect_and_send_first_request,3,[{file,"httpc_handler.erl"},{line,815}]},{httpc_handler,init,1,[{file,"httpc_handler.erl"},{line,238}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,247}]}]} Offender: [{pid,<0.522.0>},{id,undefined},{mfargs,{httpc_handler,start_link,undefined}},{restart_type,temporary},{shutdown,4000},{child_type,worker}]

正文长度错误/太长是对的吗，因为在我的本地程序上它运行良好？请求到servlet应该不是问题

提前致谢！

Answer 1

它正在崩溃，因为它试图调用 erlang:length/1，它需要一个列表，在一个似乎是 iolist（嵌套列表和二进制文件的混合体）的值上。

您确定您的代码段准确显示了您的构建方式吗Body？

Answer 2

exception error: bad argument:
[{erlang,length,[
    [100,101,118,105,99,101,84,111,107,101,110,61,
     <<"dy....[Very long FCM token]...Kn4b1">>,
     38,115,101,110,100,101,114,61|<<"epeued7o3z">>]
    ]                             ^
                                  |
 This create an improper list that make the function length/1 fail.

您定义了一个不正确的列表，因为在 cons 运算符之后的最后一项：<<"epeued7o3z">> 是二进制，而不是列表。

你可以这样写：

[100,101,118,105,99,101,84,111,107,101,110,61,
 <<"dy....[Very long FCM token]...Kn4b1">>,
 38,115,101,110,100,101,114,61,
 <<"epeued7o3z">>
]

或

[100,101,118,105,99,101,84,111,107,101,110,61,
 <<"dy....[Very long FCM token]...Kn4b1">>,
 38,115,101,110,100,101,114,61|"epeued7o3z"
]

调用length/1会returniolist的长度，注意长度是不同的，第一个list长度是22，而第二个是31。

如果你需要一个平面列表而不是 iolist，我不知道有什么函数可以直接生成它，但是你可以先将 iolist 转换为二进制，然后再将二进制转换为列表（以及长度现在是 65):

1> IoList = [100,101,118,105,99,101,84,111,107,101,110,61,<<"dy....[Very long FCM token]...Kn4b1">>,38,115,101,110,100,101,114,61,<<"epeued7o3z">>].
[100,101,118,105,99,101,84,111,107,101,110,61,
 <<"dy....[Very long FCM token]...Kn4b1">>,38,115,101,110,
 100,101,114,61,<<"epeued7o3z">>]
2> binary_to_list(iolist_to_binary(IoList)).
"deviceToken=dy....[Very long FCM token]...Kn4b1&sender=epeued7o3z"

httpc 请求：错误的参数异常长度

httpc request: Bad argument exception length

erlang

ejabberd