Step 3: Parse the request

This function uses both the HttpServiceRequest and StringTokenizer classes and methods to parse the request into the reqInfoTyp record.

FUNCTION getReqInfo(req)

Define the variables needed. The variable req references the instance of the HTTP service request object. The variables str, val, token, and i are used when parsing out details with the StringTokenizer classes and methods.

DEFINE req com.HttpServiceRequest
DEFINE str, val base.StringTokenizer
DEFINE token STRING
DEFINE i INT

For the remainder of this topic, you are retrieving data from the instance of the HTTP service request object (referenced by the variable req) and populating the record variable designed to hold this data (m_reqInfo).

Initialize m_reqInfo to NULL. This ensures that there are no pre-existing values in the record variable.

INITIALIZE m_reqInfo TO NULL

Retrieve the value of the Content-Type request header. The Content-Type request header defines the format of the incoming message body. REST APIs commonly use "application/json"or "application/xml" to reveal the format of the message body. The server application anticipates the Content-Type to be either JSON or XML. The custom getHeaderByName function retrieves the value of the Content-Type header, and based on the return value, populates the input format variable (m_reqInfo.informat) with either "XML" or "JSON".

LET m_reqInfo.ctype = getHeaderByName(req,"Content-Type")
IF m_reqInfo.ctype.getIndexOf("/xml",1) THEN
    LET m_reqInfo.informat = "XML"
ELSE 
    LET m_reqInfo.informat = "JSON"
END IF

Retrieve the value for Accept request header. The Accept request header is where the client application conveys its response preference. The server application expects the Accept request header to be either JSON or XML. The custom getHeaderByName function retrieves the value of the Accept header, and based on the returned value, populates the output format variable (m_reqInfo.outformat) with either "XML" or "JSON".

LET m_reqInfo.caccept = getHeaderByName(req,"Accept")
IF m_reqInfo.caccept.getIndexOf("/xml",1) THEN
    LET m_reqInfo.outformat = "XML"
ELSE 
    LET m_reqInfo.outformat = "JSON"
END IF

Parse out the HTTP method (verb) of the HTTP service request with the function com.HttpServiceRequest.getMethod(), and populate the method variable (m_reqInfo.method) with the result.

LET m_reqInfo.method = req.getMethod()

While possible values could include GET, POST, PUT, HEAD, and DELETE, our demo server application expects GET, and the processing part of the server application code does not test or code for any verbs aside from GET.

Parse out the path and the query. Retrieve the URL resource using the function com.HttpServiceRequest.getUrl. To parse out the path and the query from the URL, call the custom parseUrl function. The path is placed in the path variable (m_reqInfo.path) and the query string is placed in the query variable (m_reqInfo.query).

CALL parseUrl(req.getUrl()) RETURNING m_reqInfo.path, m_reqInfo.query

Take the query variable (m_reqInfo.query) and parse out the value pairs using the StringTokenizer class and methods. The value pairs of variable name and value are stored in the m_reqInfo.items dynamic array.

LET str = base.StringTokenizer.create(m_reqInfo.query,"&")
LET i=1
CALL m_reqInfo.items.clear()
WHILE str.hasMoreTokens()
    LET token = str.nextToken()
    LET val = base.StringTokenizer.create(token,"=")
    IF val.hasMoreTokens() THEN LET m_reqInfo.items[i].name = val.nextToken() END IF
    IF val.hasMoreTokens() THEN LET m_reqInfo.items[i].value = val.nextToken() END IF
    LET i=i+1
END WHILE

The purpose of this function is to take as input two things:

• The HTTP service request object in an com.HttpServiceRequest variable.
• The name of the header type whose value you want to return.

To do this, the function uses the API methods getRequestHeaderCount, getRequestHeaderName, and getRequestHeaderValue against the com.HttpServiceRequest object. The function first counts the number of header requests, and then cycles through them until it finds the specific header request that is being asked for. When the match happens, the value for that header is returned; if no match is found, then NULL is returned.

FUNCTION getHeaderByName(areq,hname)
    DEFINE areq com.HttpServiceRequest
    DEFINE hname STRING

    DEFINE aname STRING
    DEFINE iname STRING
    DEFINE i INT
    DEFINE n INT

    LET aname = hname.toLowerCase()
    LET n = areq.getRequestHeaderCount()
    FOR i=1 TO n
        LET iname = areq.getRequestHeaderName(i)
        IF aname.equals(iname.toLowerCase()) THEN
            RETURN areq.getRequestHeaderValue(i)
        END IF
    END FOR

    RETURN NULL
END FUNCTION

For this function, the URL is passed in. This function divides the URL into two parts, the path (up to and including the question mark) and the query. The path and the query are then returned to the calling function.

FUNCTION parseUrl(url)
    DEFINE url STRING
    DEFINE i INT

    LET i = url.getIndexOf("?",1)
    IF i = 0 THEN 
        RETURN url, NULL
    ELSE
        RETURN url.subString(1,i), url.subString(i+1,url.getLength())
    END IF
END FUNCTION