Commercial route filters for transformations

The open-source Spring Cloud Gateway project includes a number of built-in filters for use in Gateway routes. The following commercial filters provided by Spring Cloud Gateway for VMware Tanzu can be used in addition to those included in the OSS project.

ClaimHeader

The ClaimHeader filter allows passing a JWT claim value as an HTTP Header. It works both with and without SSO activated, with the consideration that when SSO is not activated, the JWT token is expected in Authorization Header and won't be validated.

This filter is useful in scenarios where the target service does not handle JWT authorization, but still needs some piece of information from the JWT token.

The ClaimHeader filter configuration requires two parameters:

• Claim name: case sensitive name of the claim to pass.
• Header name: name of the HTTP

The following configuration shows how to extract the claim Subject and pass in an HTTP Header called X-Claim-Sub.

$ cf bind-service cook my-gateway -c '{ "routes": [ { "path": "/cook/**", "filters":["ClaimHeader=sub,X-Claim-Sub"] } ] }'

If you need to pass more than one claim, apply the filter repeatedly.

$ cf bind-service cook my-gateway -c '{ "routes": [ { "path": "/cook/**", "filters":["ClaimHeader=sub,X-Claim-Sub", "ClaimHeader=iss,X-Claim-Iss", "ClaimHeader=iat,X-Claim-Iat"] } ] }'

Note If the header is already present, the value(s) from the claim will be added to it. That is, previous values sent in the SCG request will be preserved.

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JsonToXml

This filter provides a convenient method to convert from JSON to XML. It requires that the Content-Type from the response is application/json, and it accepts one attribute to set the root tag for the XML response.

Note Applying transformations on large amounts of JSON data could affect response latency.

Note The JsonToXml filter cannot be used on the same API route where the XmlToJson filter is applied.

$ cf bind-service cook my-gateway -c '{ "routes": [ { "path": "/cook/**", "filters":["JsonToXml=custom-response"] } ] }'

In the example, if the response contains the following JSON:

{
    "test":  {
       "foo" : "test",
       "bar" : "test" }
}

It would become:

<?xml version='1.0' encoding='UTF-8'?>
<custom-response>
    <test>
         <foo>test</foo>
         <bar>test</bar>
    </test>
</custom-response>

Also, if the JSON in the original response doesn't contain a root element and no attribute wrapper is configured, it adds the wrapper response automatically.

For example:

{
  "foo" : "test",
  "bar" : "test"
}

Becomes:

<?xml version='1.0' encoding='UTF-8'?>
<response>
    <foo>test</foo>
    <bar>test</bar>
</response>

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RemoveJsonAttributesResponseBody

This filter provides a convenient method to apply a transformation to JSON body content from the target service through the gateway. It accepts a list of attribute names to search for. An optional last parameter from the list can be a boolean to remove the attributes only at root level (default value if not present at the end of the parameter configuration, false) or recursively (true).

Note Applying the recursive deletion mode on a large JSON data affects service latency.

$ cf bind-service cook my-gateway -c '{ "routes": [ { "path": "/cook/**", "filters":["RemoveJsonAttributesResponseBody=origin,foo,true"] } ] }'

In the example, the attributes origin and foo will be deleted from the JSON content body at any level.

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RewriteAllResponseHeaders

This filter provides a convenient method to apply a transformation to all headers coming from the target service through the gateway. It accepts a regular expression to search for, in header values and in the text, to replace the matching expression with.

$ cf bind-service cook my-gateway -c '{ "routes": [ { "path": "/cook/**", "filters":["RewriteAllResponseHeaders=password=[^&]+,password=***"] } ] }'

In the example, any header value containing a number (\d matches any number from 0 to 9) will be replaced by 0.

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RewriteResponseBody

This filter provides a convenient method to apply a transformation to any body content from the target service through the gateway, it won't apply any transformation to response headers. It accepts a list of regular expressions (comma-separated) to search for, in value and in text, to replace the matching expression with (colon-separated).

$ cf bind-service cook my-gateway -c '{ "routes": [ { "path": "/cook/**", "filters":["RewriteResponseBody=foo:bar,/path-one/:/path-two/"] } ] }'

In the example, in a body content of any type:

• foo will be replaced by bar
• /path-one/ will be replaced by /path-two/

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XmlToJson

This filter provides a convenient method to convert from XML to JSON. It requires that the Content-Type from the response is XML-compliant.

Note Applying transformations on large XML data could affect response latency.

Note The XmlToJson filter cannot be used on the same API route where the JsonToXml filter is applied.

$ cf bind-service cook my-gateway -c '{ "routes": [ { "path": "/cook/**", "filters":["XmlToJson"] } ] }'

In the example, if the response contains the following JSON:

<?xml version='1.0' encoding='UTF-8'?>
<test>
     <foo>test</foo>
     <bar>test</bar>
</test>

It becomes:

{
    "test":  {
       "foo" : "test",
       "bar" : "test" }
}

If the XML contains any attributes in the original response, it adds them as JSON fields.

For example:

<?xml version='1.0' encoding='UTF-8'?>
<test id="1">
    <foo>test</foo>
    <bar>test</bar>
</test>

Becomes:

{
    "test":  {
       "id": "1"
       "foo" : "test",
       "bar" : "test" }
}

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