[Cppcms-users] Can't get correct response from json rpc server when using javascript

[刘怀宇 <mys...@gm...>]

Hello
There is a json rpc example in cppcms project. Now I want to send json_rpc
request  using javascript , but it doesn't work.
 I found that the Content-Type field of the HttpRequest message must be
"application/json" for  cppcms application ,otherwise I got error messages
as follows  " invalid content type "
And I tested  successfully by python(in tests dir) and curl command

1.python:

def test(name,A,B):
    if A != B:
        print "Error :" + name
        print "-----Actual--"
        print A,"---Expected--"
        print B,"-------------"
        sys.exit(1)
    else:
        print "Ok:"+name

def test_status(h,stat):
    if h.status != stat:
        print "Status mistmatch:",h.status,"!=",stat
        sys.exit(1)

def test_valid(name,params,ans,method='POST'):
    h=httplib.HTTPConnection('192.168.30.17:8080');
    headers = {"Content-type": "application/json"}
    h.request(method,'/rpc',params,headers)
    r=h.getresponse()
    test(name,r.read(),ans)

test_valid('sum','{"method" : "sum" , "params" : [ 1, 2 ], "id" :
1}','{"id":1,"error":null,"result":3}')

2.curl command:
 curl -i -X POST --header "Content-Type:application/json" -d
'{"method":"sum","params":[1,2],"id":1}' http://192.168.30.17:8080/rpc

They both succeeded.

But I can't get correct response by using  javascript.The following code has
been tested in IE8 , Chrome13 and firefox6.It only success in IE8.

var xhr = new XMLHttpRequest();
var rpcUrl = 'http://192.168.30.17:8080/rpc';
var postData = '{"method":"sum","params":[1,2],"id":1}';

xhr.open("post", rpcUrl, true);

xhr.setRequestHeader("Content-Type","application/json");

xhr.onreadystatechange = function() {
if (xhr.readyState === 4) {
if (xhr.status >= 200 && xhr.status < 300 || xhr.status === 304) {
alert(xhr.responseText)
}
}
}
xhr.send(postData);

Maybe the problem is that I can't set the "Content-Type" as
"application/json" successfully in Chrome and Firefox.

Do you have any experience about ajax?
Or just give me an idea!