What
The HTTPModifier policy can change an existing request or response message.
The policy lets you perform the following actions on those messages:
- Add new form parameters, headers, or query parameters to a message
- Remove headers, query parameters, and form parameters from a message
- Set the value of existing properties in a message
With HTTPModifier, you can add, change, or remove properties of either the request or response. You can alternatively use HTTPModifier to create a custom request or response message and pass it to an alternative target, as described in Create custom request messages.
The HTTPModifier policy can create flow variables with the following child elements:
The order in which you organize the <Add>
, <Set>
,
and <Remove>
elements is important. The policy executes those actions in the order
in which they appear in the policy configuration. If you need to remove all headers, then set a
specific header, you should include the <Remove>
element before the <Set>
element.
This policy is a Standard policy and can be deployed to any environment type. For information on policy types and availability with each environment type, see Policy types.
<HTTPModifier>
element
Defines an HTTPModifier policy.
Default Value | See Default Policy tab, below |
Required? | Required |
Type | Complex object |
Parent Element | N/A |
Child Elements |
<Add> <AssignTo> <DisplayName> <IgnoreUnresolvedVariables> <Remove> <Set> |
The <HTTPModifier>
element uses the following syntax:
Syntax
The <HTTPModifier>
element uses the following syntax:
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <!-- All HTTPModifier child elements are optional --> <Add> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> </Add> <AssignTo createNew="[true|false]" transport="http" type="[request|response]">DESTINATION_VARIABLE_NAME</AssignTo> <DisplayName>POLICY_DISPLAY_NAME</DisplayName> <IgnoreUnresolvedVariables>[true|false]</IgnoreUnresolvedVariables> <!-- Can also be empty to remove everything from the message (<Remove/>) --> <Remove> <!-- Can also be an empty array to remove all FormParams (<FormParams/>) --> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> <!-- Can also be an empty array to remove all Headers (<Headers/>) --> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> <!-- Can also be an empty array to remove all QueryParams (<QueryParams/>) --> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> </Remove> <Set> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> <Path>PATH</Path> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> <StatusCode>HTTP_STATUS_CODE or {variable}</StatusCode> <Verb>[GET|POST|PUT|PATCH|DELETE|{variable}]</Verb> <Version>[1.0|1.1|{variable}]</Verb> </Set> </HTTPModifier>
Default Policy
The following example shows the default settings when you add an HTTPModifier policy to your flow in the Apigee UI:
<HTTPModifier continueOnError="false" enabled="true" name="http-modifier-default"> <DisplayName>HTTP Modifier-1</DisplayName> <Properties/> <Remove> <Headers> <Header name="h1"/> </Headers> <QueryParams> <QueryParam name="q1"/> </QueryParams> <FormParams> <FormParam name="f1"/> </FormParams> </Remove> <Add> <Headers/> <QueryParams/> <FormParams/> </Add> <Set> <Headers/> <QueryParams/> <FormParams/> <!-- <Verb>GET</Verb> --> <Path/> </Set> <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables> <AssignTo createNew="false" transport="http" type="request"/> </HTTPModifier>
When you insert a new HTTPModifier policy in the Apigee UI, the template contains stubs for all
possible operations. Typically, you select which operations you want to perform with this policy
and remove the rest of the child elements. For example, if you want to perform an add operation, use the
<Add>
element and remove <Remove>
and other child elements from the
policy to make it more readable.
This element has the following attributes that are common to all policies:
Attribute | Default | Required? | Description |
---|---|---|---|
name |
N/A | Required |
The internal name of the policy. The value of the Optionally, use the |
continueOnError |
false | Optional | Set to false to return an error when a policy fails. This is expected behavior for
most policies. Set to true to have flow execution continue even after a policy
fails. See also:
|
enabled |
true | Optional | Set to true to enforce the policy. Set to false to turn off the
policy. The policy will not be enforced even if it remains attached to a flow. |
async |
false | Deprecated | This attribute is deprecated. |
The following table provides a high-level description of the child elements of
<HTTPModifier>
:
Child Element | Required? | Description |
---|---|---|
Common operations | ||
<Add> |
Optional | Adds information to the message object that is specified by the
<AssignTo> element.
To overwrite existing headers or parameters, use the |
<Remove> |
Optional | Deletes the specified elements from the message variable specified in the
<AssignTo> element. |
<Set> |
Optional | Replaces values of existing properties on the request or response, which is specified by
the <AssignTo> element.
|
Other child elements | ||
<AssignTo> |
Optional | Specifies which message the HTTPModifier policy operates on. This can be the standard request or response, or it can be a new custom message. |
<IgnoreUnresolvedVariables> |
Optional | Determines whether processing stops when an unresolved variable is encountered. |
Each of these child elements is described in the sections that follow.
Examples
The following examples show some of the ways in which you can use the HTTPModifier policy:
1: Add header
The following example adds a header to the request with the
<Add>
element. The VerifyAPIKey variable in this example is generated
by the VerifyAPIKey policy:
<HTTPModifier name="HM-add-headers-1"> <Add> <Headers> <Header name="partner-id">{verifyapikey.VAK-1.developer.app.partner-id}</Header> </Headers> </Add> <AssignTo>request</AssignTo> </HTTPModifier>
2: Modify response
The following example modifies an existing response object by adding a header to it:
<HTTPModifier name="HM-modify-response"> <Set> <Headers> <Header name="Cache-Hit">{lookupcache.LookupCache-1.cachehit}</Header> </Headers> </Set> <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables> <AssignTo>response</AssignTo> </HTTPModifier>
This example does not create a new message. Instead, it modifies an existing response message by adding an HTTP header.
Because this example specifies response
as the variable name in the
<AssignTo>
element, this policy modifies the response object that was originally
set with data returned by the target server.
The HTTP header added to the response message by this policy is derived from a variable populated by the LookupCache policy. Therefore the response message modified by this HTTPModifier policy contains an HTTP header that indicates whether the results have been pulled from the cache or not. Setting headers in the response can be handy for debugging and troubleshooting.
3: Remove query param
The following example removes the apikey
query parameter from the request:
<HTTPModifier name="HM-remove-query-param"> <Remove> <QueryParams> <QueryParam name="apikey"/> </QueryParams> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
It's a best practice to strip the apikey
query parameter from the request
message when you use the VerifyAPIKey policy for user authentication. You do this to prevent
sensitive key information from being passed to the backend target.
Child element reference
This section describes the child elements of <HTTPModifier>
.
<Add>
Adds information to the request or response, which is specified by the <AssignTo>
element.
The <Add>
element adds new properties on the message that don't exist in the original
message. Note that <Set>
also provides this functionality. To change the values of
existing properties, use the <Set>
element.
Default Value | N/A |
Required? | Optional |
Type | Complex type |
Parent Element |
<HTTPModifier>
|
Child Elements |
<FormParams> <Headers> <QueryParams> |
The <Add>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Add> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> </Add> </HTTPModifier>
Example 1
The following example uses the <FormParams>
element to get the values of
three query string parameters from the initial request and set them as form parameters on the
target endpoint request:
<HTTPModifier name="HM-add-formparams-3"> <Add> <FormParams> <FormParam name="username">{request.queryparam.name}</FormParam> <FormParam name="zip_code">{request.queryparam.zipCode}</FormParam> <FormParam name="default_language">{request.queryparam.lang}</FormParam> </FormParams> </Add> <Remove> <QueryParams/> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
Example 2
The following example uses the <Headers>
element to add a
partner-id
header to the request that will be sent to the target endpoint:
<HTTPModifier name="HM-add-headers-1"> <Add> <Headers> <Header name="partner-id">{verifyapikey.VAK-1.developer.app.partner-id}</Header> </Headers> </Add> <AssignTo>request</AssignTo> </HTTPModifier>
Example 3
The following example uses the <QueryParams>
element to add a single query
parameter with a static value to the request:
<HTTPModifier name="HM-add-queryparams-1"> <Add> <QueryParams> <QueryParam name="myParam">42</QueryParam> </QueryParams> </Add> <AssignTo>request</AssignTo> </HTTPModifier>
This example uses <Add>
in the request preflow. If you look at the results in a tool
such as the Debug tool, the request to https://example-target.com/get
becomes
https://example-target.com/get?myParam=42
.
The child elements of <Add>
support dynamic string substitution, known as
message templating.
<FormParams>
(child of <Add>
)
Adds new form parameters to the request message. This element has no effect on a response message.
Default Value | N/A |
Required? | Optional |
Type | Array of <FormParam> elements |
Parent Element |
<Add>
|
Child Elements |
<FormParam> |
The <FormParams>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Add> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> <AssignTo createNew="[true|false]" transport="http" type="[request|response]">DESTINATION_VARIABLE_NAME</AssignTo> </Add> </HTTPModifier>
Example 1
The following example adds a single form parameter (answer
) and a static value (42
) to
the request:
<HTTPModifier name="HM-add-formparams-1"> <Add> <FormParams> <FormParam name="answer">42</FormParam> </FormParams> </Add> <AssignTo>request</AssignTo> </HTTPModifier>
Example 2
The following example gets the value of the name
query parameter and
adds it to the request as a form parameter, and then removes the query parameter:
<HTTPModifier name="HM-Swap-QueryParam-to-FormParams"> <Add> <FormParam name="name">{request.queryparam.name} </Add> <Remove> <QueryParam name="name"/> </Remove> </HTTPModifier>
Note that this example does not specify a target with <AssignTo>
. This policy adds the
parameter to the request only.
Example 3
The following example adds multiple form parameters to the request:
<HTTPModifier name="HM-add-formparams-3"> <Add> <FormParams> <FormParam name="username">{request.queryparam.name}</FormParam> <FormParam name="zip_code">{request.queryparam.zipCode}</FormParam> <FormParam name="default_language">{request.queryparam.lang}</FormParam> </FormParams> </Add> <Remove> <QueryParams/> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
This example gets the query string parameters from the originating request and adds them as form parameters with different names. Then it removes the original query parameters. Apigee will send the modified request to the target endpoint.
You can use the Debug tool to look at the flow. You'll see that the body of the request contains the URL-encoded form data, which was originally passed in as query string parameters:
username=nick&zip_code=90210&default_language=en
You can use <FormParams>
only when the following criteria are met:
- HTTP verbs:
GET
,POST
- Message type: Request
- One (or both) of the following:
- Form data: Set to some value, or
""
(the empty string). For example, withcurl
, add-d ""
to your request. Content-Length
header: Set to 0 (if no data is in the original request; otherwise, the current length, in bytes). For example, withcurl
add-H "Content-Length: 0"
to your request.
- Form data: Set to some value, or
For example:
curl -vL -X POST -d "" -H "Content-Type: application/x-www-form-urlencoded" https://ahamilton-eval-test.apigee.net/am-test
When you add <FormParams>
, Apigee sets the request's Content-Type
header to
application/x-www-form-urlencoded
before sending the message to the target service.
<Headers>
(child of <Add>
)
Adds new headers to the specified request or response, which is specified by the
<AssignTo>
element.
Default Value | N/A |
Required? | Optional |
Type | Array of <Header> elements |
Parent Element |
<Add>
|
Child Elements |
<Header> |
The <Headers>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Add> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> </Add> </HTTPModifier>
Example 1
The following example adds a partner-id
header to the request message, and
assigns the value of the verifyapikey.VAK-1.developer.app.partner-id
flow variable to that header.
<HTTPModifier name="HM-add-headers-1"> <Add> <Headers> <Header name="partner-id">{verifyapikey.VAK-1.developer.app.partner-id}</Header> </Headers> </Add> <AssignTo>request</AssignTo> </HTTPModifier>
<QueryParams>
(child of <Add>
)
Adds new query parameters to the request. This element has no effect on a response.
Default Value | N/A |
Required? | Optional |
Type | Array of <QueryParam> elements |
Parent Element |
<Add>
|
Child Elements |
<QueryParam> |
The <QueryParams>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Add> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> </Add> </HTTPModifier>
Example 1
The following example adds the query parameter myParam
to the request and assigns the value
42
to it:
<HTTPModifier name="HM-add-queryparams-1"> <Add> <QueryParams> <QueryParam name="myParam">42</QueryParam> </QueryParams> </Add> <AssignTo>request</AssignTo> </HTTPModifier>
You can use <QueryParams>
only when the following criteria are met:
- HTTP verbs:
GET
,POST
- Message type: Request
In addition, you can only set query parameters when the <AssignTo>
element's
type
attribute is a request message. Setting them on the response has no effect.
If you define an empty array of query parameters in your policy
(<Add><QueryParams/></Add>
), the policy does not add any query
parameters. This is the same as omitting <QueryParams>
.
<AssignTo>
Determines which object the HTTPModifier policy operates on. The options are:
- Request message: The
request
received by the API proxy - Response message: The
response
returned from the target server - Custom message: A custom request or response object
Note that in some cases, you cannot change the object on which the HTTPModifier policy acts.
For example, you cannot use <Add>
or <Set>
to add or change query parameters
(<QueryParams>
) or form parameters (<FormParams>
) on the response. You can only
manipulate query parameters and form parameters on the request.
Default Value | N/A |
Required? | Optional |
Type | String |
Parent Element |
<HTTPModifier>
|
Child Elements | None |
If you do not specify <AssignTo>
, or if you specify the <AssignTo>
element but do
not specify a text value for the element, the policy acts on the default request or response,
which is based on where the policy executes. If the policy executes in the request flow, it
affects the request message. If it executes in the response flow, the policy affects the response
by default.
The <AssignTo>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <AssignTo createNew="[true|false]" transport="http" type="[request|response]">DESTINATION_VARIABLE_NAME</AssignTo> </HTTPModifier>
Example 1
The following example specifies no message in the text of the <AssignTo>
. That implies
that the policy will act on either the request
or response
message,
depending on where the policy executes.
<HTTPModifier name="assignto-1"> <AssignTo createNew="false" transport="http" type="request"/>-- no-op --> ... </HTTPModifier>
If you specify createNew="false"
, and do not explicitly provide a message name,
the other attributes of <AssignTo>
are irrelevant. In this case, you may
wish to omit the <AssignTo>
element completely.
Example 2
The following example creates a new request object, over-writing the existing object:
<HTTPModifier name="assignto-2"> <AssignTo createNew="true" transport="http" type="request"/> ... </HTTPModifier>
When you create a new request or response object, the other elements of the HTTPModifier
policy (such as <Add>
and <Set>
act on that new
request object.
You can access the new request object in other policies later in the flow, or send the new request object to an external service with a ServiceCallout policy.
Example 3
The following example creates a new request object named MyRequestObject
:
<HTTPModifier name="assignto-3"> <AssignTo createNew="true" transport="http" type="request">MyRequestObject</AssignTo> ... </HTTPModifier>
When you create a new request or response object, the other elements of the HTTPModifier
policy (such as <Add>
and <Set>
act on that new
request object.
You can access the new request object by name in other policies later in the flow, or send the new request object to an external service with a ServiceCallout policy.
The following table describes the attributes of <AssignTo>
:
Attribute | Description | Required? | Type |
---|---|---|---|
createNew |
Determines whether this policy creates a new message when assigning values. If If
If
|
Optional | Boolean |
transport |
Specifies the transport type for the request or response message type. The default value is |
Optional | String |
type |
Specifies the type of the new message, when createNew is true . Valid
values are request or response .
The default value is |
Optional | String |
<DisplayName>
Use in addition to the name
attribute to label the policy in the
management UI proxy editor with a different, more natural-sounding name.
The <DisplayName>
element is common to all policies.
Default Value | N/A |
Required? | Optional. If you omit <DisplayName> , the value of the
policy's name attribute is used. |
Type | String |
Parent Element | <PolicyElement> |
Child Elements | None |
The <DisplayName>
element uses the following syntax:
Syntax
<PolicyElement> <DisplayName>POLICY_DISPLAY_NAME</DisplayName> ... </PolicyElement>
Example
<PolicyElement> <DisplayName>My Validation Policy</DisplayName> </PolicyElement>
The <DisplayName>
element has no attributes or child elements.
<IgnoreUnresolvedVariables>
Determines whether processing stops when an unresolved variable is encountered.
Default Value | False |
Required? | Optional |
Type | Boolean |
Parent Element |
<HTTPModifier>
|
Child Elements | None |
Set to true
to ignore unresolved variables and continue processing; otherwise
false
. The default value is false
.
Setting <IgnoreUnresolvedVariables>
to true
is different from setting the <HTTPModifier>
's
continueOnError
to true
in that it is specific to setting and getting values of
variables. If you set continueOnError
to true
, then Apigee ignores all errors, not
just errors encountered when using variables.
The <IgnoreUnresolvedVariables>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <IgnoreUnresolvedVariables>[true|false]</IgnoreUnresolvedVariables> </HTTPModifier>
Example 1
The following example sets <IgnoreUnresolvedVariables>
to true
:
<HTTPModifier name="HM-Set-Headers"> <Set> <Headers> <Header name='new-header'>{possibly-defined-variable}<Header> </Headers> </Set> <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables> </HTTPModifier>
Because <IgnoreUnresolvedVariables>
is set to true
, if
the possibly-defined-variable
variable is not defined, this policy will
not throw a fault.
<Remove>
Removes headers, query parameters, or form parameters from a message. An empty tag removes all corresponding parameters including headers, formparams, and queryparams.
The affected message can be a request or a response. You specify which message <Remove>
acts on by using the <AssignTo>
element.
Default Value | N/A |
Required? | Optional |
Type | Complex type |
Parent Element |
<HTTPModifier>
|
Child Elements |
<FormParams> <Headers> <QueryParams> |
A common use case for <Remove>
is to delete a query parameter or header that contains sensitive
information from the incoming request object, to avoid passing it to the backend server.
The <Remove>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <!-- Can also be empty to remove everything from the message (<Remove/>) --> <Remove> <!-- Can also be an empty array to remove all FormParams (<FormParams/>) --> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> <!-- Can also be an empty array to remove all Headers (<Headers/>) --> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> <!-- Can also be an empty array to remove all QueryParams (<QueryParams/>) --> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> </Remove> </HTTPModifier>
Example 1
The following example removes all form parameters and a query parameter from
the request
object:
<HTTPModifier name="HM-remove-2"> <Remove> <!-- Empty (<FormParams/>) removes all form parameters --> <FormParams/> <QueryParams> <QueryParam name="qp1"/> </QueryParams> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
Example 2
The following example removes everything from a message object:
<HTTPModifier name="HM-remove-3"> <Remove/> <AssignTo>request</AssignTo> </HTTPModifier>
Typically you would do this only if you were going to use the <Set>
element to
set some replacement values into the message.
<FormParams>
(child of <Remove>
)
Removes the specified form parameters from the request. This element has no effect on a response.
Default Value | N/A |
Required? | Optional |
Type | Array of <FormParam> elements or an empty array |
Parent Element |
<Remove>
|
Child Elements |
<FormParam> |
The <FormParams>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <!-- Can also be empty to remove everything from the message (<Remove/>) --> <Remove> <!-- Can also be an empty array to remove all FormParams (<FormParams/>) --> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> </Remove> </HTTPModifier>
Example 1
The following example removes three form parameters from the request:
<HTTPModifier name="HM-remove-formparams-1"> <Remove> <FormParams> <FormParam name="form_param_1"/> <FormParam name="form_param_2"/> <FormParam name="form_param_3"/> </FormParams> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
Example 2
The following example removes all form parameters from the request:
<HTTPModifier name="HM-remove-formparams-2"> <Remove> <FormParams/> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
Example 3
If there are multiple form params with the same name, use the following syntax:
<HTTPModifier name="HM-remove-formparams-3"> <Remove> <FormParams> <FormParam name="f1"/> <FormParam name="f2"/> <FormParam name="f3.2"/> </FormParams> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
This example removes f1
, f2
, and the second value of f3
. If f3
has only one
value, then it is not removed.
You can use <FormParams>
only when the following criteria are met:
- Message type: Request
Content-Type
:application/x-www-form-urlencoded
<Headers>
(child of <Remove>
)
Removes the specified HTTP headers from the request or response, which is specified by the
<AssignTo>
element.
Default Value | N/A |
Required? | Optional |
Type | Array of <Header> elements or an empty array |
Parent Element |
<Remove>
|
Child Elements |
<Header> |
The <Headers>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <!-- Can also be empty to remove everything from the message (<Remove/>) --> <Remove> <!-- Can also be an empty array to remove all Headers (<Headers/>) --> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> </Remove> </HTTPModifier>
Example 1
The following example removes the user-agent
header from the request:
<HTTPModifier name="HM-remove-one-header"> <Remove> <Headers> <Header name="user-agent"/> </Headers> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
Example 2
The following example removes all headers from the request:
<HTTPModifier name="HM-remove-all-headers"> <Remove> <Headers/> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
Example 3
If there are multiple headers with the same name, use the following syntax:
<HTTPModifier name="HM-remove-headers-3"> <Remove> <Headers> <Header name="h1"/> <Header name="h2"/> <Header name="h3.2"/> </Headers> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
This example removes h1
, h2
, and the second value of h3
from the request. If h3
has only one value, then it is not removed.
<QueryParams>
(child of <Remove>
)
Removes the specified query parameters from the request. This element has no effect on a response.
Default Value | N/A |
Required? | Optional |
Type | Array of <QueryParam> elements or an empty array |
Parent Element |
<Remove>
|
Child Elements |
<QueryParam> |
The <QueryParams>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <!-- Can also be empty to remove everything from the message (<Remove/>) --> <Remove> <!-- Can also be an empty array to remove all QueryParams (<QueryParams/>) --> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> </Remove> </HTTPModifier>
Example 1
The following example removes a single query parameter from the request:
<HTTPModifier name="HM-remove-queryparams-1"> <Remove> <QueryParams> <QueryParam name="qp1"/> </QueryParams> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
Example 2
The following example removes all query parameters from the request:
<HTTPModifier name="HM-remove-queryparams-2"> &tl;Remove> <QueryParams/> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
Example 3
If there are multiple query params with the same name, use the following syntax:
<HTTPModifier name="HM-remove-queryparams-3"> <Remove> <QueryParams> <QueryParam name="qp1"/> <QueryParam name="qp2"/> <QueryParam name="qp3.2"/> </QueryParams> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
This example removes qp1
, qp2
, and the second value of qp3
from the request. If
qp3
has only one value, then it is not removed.
Example 4
The following example removes the apikey
query parameter from the request:
<HTTPModifier name="HM-remove-query-param"> <Remove> <QueryParams> <QueryParam name="apikey"/> </QueryParams> </Remove> <AssignTo>request</AssignTo> </HTTPModifier>
You can use <QueryParams>
only when the following criteria are met:
- HTTP verbs:
GET
,POST
- Message type: Request
<Set>
Sets information in the request or response message, which is specified by the
<AssignTo>
element. <Set>
overwrites headers or
query or form parameters that already exist in the original message or adds new if they don't.
Headers and query and form parameters in an HTTP message may hold multiple values. To add
additional values for a header or parameter, use the <Add>
element instead.
Default Value | N/A |
Required? | Optional |
Type | Complex type |
Parent Element |
<HTTPModifier>
|
Child Elements |
<FormParams> <Headers> <Path> <QueryParams> <StatusCode> <Verb> <Version> |
The <Set>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Set> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> <Path>PATH</Path> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> <StatusCode>HTTP_STATUS_CODE or {variable}</StatusCode> <Verb>[GET|POST|PUT|PATCH|DELETE|{variable}]</Verb> <Version>[1.0|1.1|{variable}]</Verb> </Set> </HTTPModifier>
Example
The following example sets a specific header. When this policy is attached in the Request flow, it will allow the upstream system to receive an additional header that was not included in the original inbound request.
<HTTPModifier name="HM-Set-Header"> <Set> <Headers> <Header name="authenticated-developer">{verifyapikey.VAK-1.developer.id}</Header> </Headers> </Set> <AssignTo>request</AssignTo> </HTTPModifier>
<FormParams>
(child of <Set>
)
Overwrites existing form parameters on a request and replaces them with the new values that you specify with this element. This element has no effect on a response.
Default Value | N/A |
Required? | Optional |
Type | Array of <FormParam> elements |
Parent Element |
<Set>
|
Child Elements |
<FormParam> |
The <FormParams>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Set> <FormParams> <FormParam name="FORMPARAM_NAME">FORMPARAM_VALUE</FormParam> ... </FormParams> </Set> </HTTPModifier>
Example 1
The following example sets a form parameter called myparam
to the value of the
request.header.myparam
variable in a new, custom request:
<HTTPModifier name="HM-set-formparams-1"> <Set> <FormParams> <FormParam name="myparam">{request.header.myparam}</FormParam> </FormParams> </Set> <AssignTo createNew="true" transport="http" type="request>>MyCustomRequest</AssignTo> </HTTPModifier>
You can use <FormParams>
only when the following criteria are met:
- HTTP verb:
POST
- Message type: Request
If you define empty form parameters in your policy
(<Add><FormParams/></Add>
), the policy does not add any form
parameters. This is the same as omitting the <FormParams>
.
<Set>
changes the Content-Type
of the message to
application/x-www-form-urlencoded
before sending it to the target endpoint.
<Headers>
(child of <Set>
)
Overwrites existing HTTP headers in the request or response, which is specified by the
<AssignTo>
element.
Default Value | N/A |
Required? | Optional |
Type | Array of <Header> elements |
Parent Element |
<Set>
|
Child Elements |
<Header> |
The <Headers>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Set> <Headers> <Header name="HEADER_NAME">HEADER_VALUE</Header> ... </Headers> </Set> </HTTPModifier>
Example 1
The following example sets the x-ratelimit-remaining
header to the value of the
ratelimit.Quota-1.available.count
variable:
<HTTPModifier name="HM-Set-RateLimit-Header"> <Set> <Headers> <Header name="X-RateLimit-Remaining">{ratelimit.Quota-1.available.count}</Header> </Headers> </Set> <AssignTo>response</AssignTo> </HTTPModifier>
If you define empty headers in your policy
(<Set><Headers/></Set>
), the policy does not set any headers. This
will have the same effect as omitting <Headers>
.
<Path>
(child of <Set>
)
<QueryParams>
(child of <Set>
)
Overwrites existing query parameters in the request with new values. This element has no effect on a response.
Default Value | N/A |
Required? | Optional |
Type | Array of <QueryParam> elements |
Parent Element |
<Set>
|
Child Elements |
<QueryParam> |
The <QueryParams>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Set> <QueryParams> <QueryParam name="QUERYPARAM_NAME">QUERYPARAM_VALUE</QueryParam> ... </QueryParams> </Set> </HTTPModifier>
Example 1
The following example sets the address
query parameter to the value of the
request.header.address
variable:
<HTTPModifier name="HM-set-queryparams-1"> <Set> <QueryParams> <QueryParam name="address">{request.header.address}</QueryParam> </QueryParams> </Set> </HTTPModifier>
You can use <QueryParams>
only when the following criteria are met:
- HTTP verbs:
GET
,POST
- Message type: Request
If you define empty query parameters in your policy
(<Set><QueryParams/></Set>
), the policy does not set any query
parameters. This is the same as omitting <QueryParams>
.
<StatusCode>
(child of <Set>
)
Sets the status code on the response. This element has no effect on a request.
Default Value | '200' (when <AssignTo> 's createNew attribute
is set to 'true') |
Required? | Optional |
Type | String or VARIABLE |
Parent Element |
<Set>
|
Child Elements | None |
The <StatusCode>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Set> <StatusCode>HTTP_STATUS_CODE or {variable}</StatusCode> </Set> </HTTPModifier>
Example 1
The following example sets a simple status code:
<HTTPModifier name="HM-set-statuscode-404"> <Set> <StatusCode>404<<StatusCode> </Set> <AssignTo>response</AssignTo> </HTTPModifier>
Example 2
The content of <StatusCode>
is treated as a message template. This means a
variable name wrapped in curly braces will be replaced at runtime with the value of the
referenced variable, as the following example shows:
<HTTPModifier name="set-statuscode-2"> <Set> <StatusCode>{calloutresponse.status.code}</StatusCode> </Set> <AssignTo>response</AssignTo> </HTTPModifier>
You can use <StatusCode>
only when the following criteria are met:
- Message type: Response
<Verb>
(child of <Set>
)
Sets the HTTP verb on the request. This element has no effect on a response.
Default Value | N/A |
Required? | Optional |
Type | String or VARIABLE |
Parent Element |
<Set>
|
Child Elements | None |
The <Verb>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Set> <Verb>[GET|POST|PUT|PATCH|DELETE|{variable}]</Verb> </Set> </HTTPModifier>
Example 1
The following example sets a simple verb on the request:
<HTTPModifier name="HM-set-verb-1"> <Set> <Verb>POST</Verb> </Set> <AssignTo>request</AssignTo> </HTTPModifier>
Example 2
The content of <Verb>
is treated as a message template. This means a variable name
wrapped in curly braces will be replaced at runtime with the value of the referenced
variable.
The following example uses a variable to populate a verb:
<HTTPModifier name="HM-set-verb-to-dynamic-value"> <Set> <Verb>{my_variable}</Verb> </Set> <AssignTo>request</AssignTo> </HTTPModifier>
You can use <Verb>
only when the following criteria are met:
- Message type: Request
<Version>
(child of <Set>
)
Sets the HTTP version on a request. This element has no effect on a response.
Default Value | N/A |
Required? | Optional |
Type | String or VARIABLE |
Parent Element |
<Set>
|
Child Elements | None |
The <Version>
element uses the following syntax:
Syntax
<HTTPModifier continueOnError="[false|true]" enabled="[true|false]" name="POLICY_NAME" > <Set> <Version>[1.0|1.1|{variable}]</Verb> </Set> </HTTPModifier>
Example 1
The following example sets the version number to 1.1
:
<HTTPModifier name="HM-set-version-1"> <Set> <Version>1.1</Version> </Set> </HTTPModifier>
Example 2
The following uses a variable in curly braces to set the version number:
<HTTPModifier name="HM-set-version-2"> <Set> <Version>{my_version}</Version> </Set> <AssignTo>request</AssignTo> </HTTPModifier>
The content of <Version>
is treated as a message template. This means a
variable name wrapped in curly braces will be replaced at runtime with the value of the referenced
variable.
You can use <Version>
only when the following criteria are met:
- Message type: Request
Create custom request messages
You can use HTTPModifier to create a custom request message. After you create a custom request, you can use it in the following ways:
- Access its variables in other policies
- Pass it to an external service
To create a custom request message, use the <AssignTo>
element in your HTTPModifier
policy. Set createNew
to true
and specify the name of the new message in the body
of the element, as the following example shows:
<HTTPModifier name="assignto-3"> <AssignTo createNew="true" transport="http" type="request">MyRequestObject</AssignTo> ... </HTTPModifier>
By default, Apigee does nothing with the custom request message. After creating it, Apigee will continue through the flow with the original request. To use the custom request, add a policy such that uses the request message and explicitly reference the newly created request message in the configuration for that policy. This would allow you to pass the custom request to an external service endpoint.
The following examples create custom request messages:
Example 1
The following example creates a custom request object with HTTPModifier:
<HTTPModifier name="HTTPModifier-3"> <AssignTo createNew="true" type="request">MyCustomRequest</AssignTo> <Set> <QueryParams> <QueryParam name="address">{request.queryparam.addy}</QueryParam> </QueryParams> <Verb>GET</Verb> </Set> <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables> </HTTPModifier>
This example:
- Creates a new request message object called
MyCustomRequest
. - On MyCustomRequest, this policy:
- Sets the
address
query parameter on the custom message to the value of the incoming request'saddy
query parameter. - Sets the HTTP verb to
GET
.
- Sets the
- Sets
<IgnoreUnresolvedVariables>
tofalse
. When<IgnoreUnresolvedVariables>
isfalse
, if one of the variables referenced in the policy configuration does not exist, Apigee will enter fault state in the API flow.
Example 2
Here's another example demonstrating how to create a custom request object with HTTPModifier:
<HTTPModifier name="HTTPModifier-2"> <AssignTo createNew="true" type="request">partner.request</AssignTo> <Set> <Verb>POST</Verb> </Set> </HTTPModifier>
This example creates a new custom request called partner.request
. It then sets the
<Verb>
on the new request.
You can access the various properties of a custom message in another HTTPModifier policy that occurs later in the flow. The following example gets the value of a header from a named custom response, and places it into a new header in the request message:
<HTTPModifier name="HM-Set-Header"> <AssignTo>request</AssignTo> <Set> <Headers> <Header name="injected-approval-id">{MyCalloutResponse.header.approval-id}</Header> </Headers> </Set> </HTTPModifier>
Error codes
This section describes the fault codes and error messages that are returned and fault variables that are set by Apigee when this policy triggers an error. This information is important to know if you are developing fault rules to handle faults. To learn more, see What you need to know about policy errors and Handling faults.
Runtime errors
These errors can occur when the policy executes.
Fault code | HTTP status | Cause | Fix |
---|---|---|---|
entities.UnresolvedVariable |
500 |
Message Template Variable in Undefined or out of scope. | |
steps.httpmodifier.InvalidStatusCode |
500 |
The resolved value of the status code is not valid. See the fault string for more information. | build |
Deployment errors
These errors can occur when you deploy a proxy containing this policy.
Error name | Cause | Fix |
---|---|---|
InvalidIndex |
If the index specified in the <Remove> elements of the
HTTPModifier policy is 0 or a negative number, then deployment
of the API Proxy fails. |
build |
Fault variables
These variables are set when this policy triggers an error at runtime. For more information, see What you need to know about policy errors.
Variables | Where | Example |
---|---|---|
httpmodifier.POLICY_NAME.failed |
POLICY_NAME is the user-specified name of the policy that threw the fault. | httpmodifier.HM-SetResponse.failed = true |
Example error response
{ "fault":{ "detail":{ "errorcode":"steps.httpmodifier.InvalidStatusCode" }, "faultstring":"HTTPModifier[HM-SetResponse]: Invalid status code bad_request" } }
Example fault rule
<FaultRule name="HTTPModifier Faults"> <Step> <Name>HM-CustomNonMessageTypeErrorResponse</Name> <Condition>(fault.name Matches "InvalidStatusCode")</Condition> </Step> <Condition>(httpmodifier.failed = true)</Condition> </FaultRule>
Schemas
Each policy type is defined by an XML schema (.xsd
). For reference,
policy schemas
are available on GitHub.