Working with HTTP flows

You might find it useful to read this information with the Web services scenarios section.

• Using secure connections with HTTPS
• Using HTTP asynchronous request-response
• Setting the HTTP Status Code for a reply
• Using LocalEnvironment.Destination.HTTP.RequestIdentifier
• Setting the HTTPRequest node URL dynamically
• Setting Generate default HTTP headers from reply or response for the HTTPReply node
• Setting Generate default HTTP headers from input for the HTTPRequest node

You can use ProxyConnectHeaders only with HTTPS (SSL) connections; these headers do not work with HTTP connections.

Using secure connections with HTTPS

For information about setting up HTTPS connections, see Implementing SSL authentication.

Using HTTP asynchronous request-response

To make an HTTP request and receive a response asynchronously, use the HTTPAsyncRequest and HTTPAsyncResponse nodes in your message flow. The HTTPAsyncRequest node processes the next message without waiting for the response, which is received by the HTTPAsyncResponse node on a different thread and in a new transaction. This means that many more requests can be processed using fewer threads.

For more information, see Using HTTP asynchronous request-response.

Setting the HTTP Status Code for a reply

The default HTTP Status Code is 200, which indicates success. If you want a different status code to be returned, take one of the following actions:

• Set your status code in the field Destination.HTTP.ReplyStatusCode in the local environment tree (correlation name OutputLocalEnvironment). This field overrides any status code that is set in an HTTPResponseHeader header. This action is the preferred option, because it provides the greatest flexibility.
• Set your status code in the field X-Original-HTTP-Status-Code in the HTTPReplyHeader header.
• Set your status code in the field X-Original-HTTP-Status-Code in the HTTPResponseHeader header. This option is useful if you include an HTTPRequest node before the HTTPReply node in your flow, because the HTTPResponseHeader header is created for you. In this scenario, an HTTPResponseHeader header has been created in the logical tree, representing the HTTP headers in the response from another web service. If you have selected the Generate default HTTP headers from reply or response property on the HTTPReply node, values for the response header are set as default values when the reply message is created.

Using LocalEnvironment.Destination.HTTP.RequestIdentifier

When the HTTPInput node receives an input request message, it sets the local environment field Destination.HTTP.RequestIdentifier to a unique value that identifies the web service client that sent the request. You can refer to this value, and you can save it to another location if appropriate.

For example, if you design a pair of message flows that interact with an existing IBM MQ application (as described in Integration node calls existing web service), you can save the identifier value in the request flow, and restore it in the reply flow, to ensure that the correct client receives the reply. If you use this technique, you must not change the data, and you must retain the data as a BLOB.

The HTTPReply node extracts the identifier value from the local environment tree and sets up the reply so that it is sent to the specific client. However, if you are using an HTTPReply node in a flow that does not have an HTTPInput node, and this field has been deleted or set incorrectly, message BIP3143S is issued.

If you design a message flow that includes both an HTTPInput and an HTTPReply node, the identifier value is set into the local environment by the HTTPInput node, but the HTTPReply node does not use it. Therefore, if your message flow includes both HTTP nodes and a Compute node in the same flow, you do not have to include the local environment tree when you specify which components of the message tree are copied from input message to output message by the Compute node (the Compute mode property).

Setting the HTTP request URL dynamically

You can set the property Default web service URL on the HTTPRequest or HTTPAsyncRequest node to determine the destination URL for a web service request. You can configure a Compute node before the HTTPRequest or HTTPAsyncRequest node within the message flow to override the value set in the property. Code ESQL that stores a URL string in LocalEnvironment.Destination.HTTP.RequestURL; the node retrieves and uses the URL string in place of the node property value.

Although you can also set the request URL in the special header X-Original-HTTP-URL in the HTTPRequestHeader header section of the request message (which overrides all other settings) in a Compute node, use the local environment tree content for this purpose for greater flexibility.

Setting Generate default HTTP headers from reply or response for the HTTPReply node

If you select Generate default HTTP headers from reply or response in the HTTPReply node properties, the node includes a minimum set of headers in the response that is sent to the web service client.

To set headers explicitly, create them in an HTTPReplyHeader header. For example, a Compute node propagates a message in the XMLNSC domain and modifies the Content-Type as follows:

CALL CopyMessageHeaders();
SET OutputRoot.HTTPReplyHeader."Content-Type" = 'text/xml';
SET OutputRoot.XMLNSC = InputRoot.XMLNSC;

Do not use the ContentType property to set the Content-Type unless you are working in the MIME domain. The ContentType property is intended to set the value of Content-Type used in MIME.

The full set of HTTP headers used in the reply is built by selecting the headers using the algorithm defined in the following steps:

1. Select one or more headers in an HTTPReplyHeader header.
2. If no Content-Type header is yet defined, create one by using a non-empty value in the ContentType property.
3. Select one or more headers in an HTTPResponseHeader header (an HTTPResponseHeader header is propagated on return from an HTTPRequest node).
4. If no Content-Type header is yet defined, create one with the default value text/xml; charset=ccsid of the message body.
5. Create or overwrite the Content-Length header.

Attention: The HTTPReply node always rewrites the Content-Length header, even if you have cleared Generate default HTTP headers from reply or response. This action ensures that the content is correct.

If an HTTPReplyHeader header section existed in the message received by the HTTPReply node, and the Output terminal of the HTTPReply node is connected, the HTTPReplyHeader header section is updated with all changed or added values.

Setting Generate default HTTP headers from input for the HTTPRequest or HTTPAsyncRequest node

If you select Generate default HTTP headers from input in the HTTPRequest or HTTPAsyncRequest node properties, the node includes a minimum set of headers in the request that is sent to the server.

To explicitly set headers, create them in an HTTPRequestHeader header. For example, a Compute node propagating a message in the XMLNSC domain can modify the Content-Type as follows:

CALL CopyMessageHeaders();
SET OutputRoot.HTTPRequestHeader."Content-Type" = 'text/xml';
SET OutputRoot.XMLNSC = InputRoot.XMLNSC;

Do not use the ContentType property to set the Content-Type unless you are working in the MIME domain. The ContentType property is intended to set the value of Content-Type used in MIME.

The full set of HTTP headers used in the request is built by selecting the headers using the algorithm defined in the following steps:

1. Set the Host header, based on either the request URL or the incoming HTTPRequestHeader header section of the message.
2. Select one or more headers in an HTTPRequestHeader header.
3. If no Content-Type header is yet defined, create one by using a non-empty value in the ContentType property.
4. Select one or more headers in an HTTPInputHeader header (an HTTPInputHeader header is created automatically by an HTTPInput node).
5. If no Content-Type header is yet defined, create one with the default value text/xml; charset=ccsid of the message body
6. If no SOAPAction header is yet defined, create one with the default value ''.
7. Create or overwrite the Content-Length header.

Attention: The HTTPRequest or HTTPAsyncRequest node always rewrites the Content-Length header, even if you have cleared Generate default HTTP headers from input or request. This action ensures that the content is correct.

If an HTTPRequestHeader header exists in the received message, the HTTPRequestHeader header is updated with all changed or added values.