Request Server - basics

Let's make things really simple.

• A Request Server is a module that supplies static data to the front end of your application.
• You define your application's Request Server in a kotlin script file application-name-reqrep.kts. This file should be in the application-name-script-config module.
• In this file, you define specific requestReply codeblocks, each of which is designed to supply different sets of data; this could be a table or view, or just a subset of the fields in a table or view.
• A requestReply can include a number of other subtleties, such as where clauses or ranges, so that you can create code that matches your precise requirements.
• If you use AppGen to build from your dictionary, then a basic kts file will be built automatically for you, covering all the tables and views in your data model. You can edit this file to add sophistication to the module.
• Otherwise, you can build your kts by defining each requestReply codeblock from scratch.

Basic definition

Here is the definition of a simple Request Server file.

• The whole content is wrapped in a single requestReplies statement. This applies no matter how many requestReply codeblocks you specify.
• In the requestReply codeblock, you must at least specify either a table or a view. In this example, we are using the table INSTRUMENT_DETAILS. A request to this Request Server will return all the fields in that table.

requestReplies {
    requestReply(INSTRUMENT_DETAILS)
}

Almost certainly, your application will need to have more than one requestReply. So, let us state the obvious and show you a file with two requestReply codeblocks. Again, each is the simplest kind you could possibly have.

requestReplies {
    requestReply(COUNTERPARTY)

    requestReply(INSTRUMENT_DETAILS)
}

Adding a name

Every requestReply in your .kts must have a unique name. If you don't give the requestReply a name, the platform will create a name, based on the table or view. In the first example above, no name has been supplied. The table used is INSTRUMENT_DETAILS, so the platform calls this requestReply REQ_INSTRUMENT_DETAILS.

It is easy to specify a name for the requestReply. For example, here we are calling our requestReply ALL_COUNTERPARTIES:

requestReplies {
    requestReply("ALL_COUNTERPARTIES", COUNTERPARTY)
    ...
}

When you run genesisInstall, the Genesis platform adds the prefix REQ_ to the name you have specified. So, in the example above, the requestReply becomes REQ_ALL_COUNTERPARTIES. That is the name you will need to use when you access this requestReply.

So, all the resources in your Request Server have names beginning with REQ_ regardless of whether you specify a name.

Specifying fields on request and reply

With all the requestReply codeblocks we have seen so far, all the fields in the table are returned.

We can add some precision using request and reply blocks within a requestReply statement.

Within a request block, you must define at least one primary key or index. In the example below, the fields ALTERNATE_TYPE AND INSTRUMENT_CODE together form the primary key.

requestReplies {
    requestReply(INSTRUMENT_DETAILS) {
        request {
            ALTERNATE_TYPE
            INSTRUMENT_CODE withAlias "ALTERNATE_CODE"
        }

        reply {
            INSTRUMENT_CODE
            INSTRUMENT_ID
            INSTRUMENT_NAME
            LAST_TRADED_PRICE
            VWAP
            SPREAD
            TRADED_CURRENCY
            EXCHANGE_ID
        }
    }
}

Note the following:

• When you do not define a request block, the primary key for the table or view is used as the default request field.
• When you do not define a reply block, all the fields will be returned.

Specifying derived fields

You can also define derived fields in a Request Server, to supplement the fields supplied by the table or view. The input for the derived field is the reply entity. All fields are available for use.

In the example below, we add a new boolean derived field:

requestReplies {
    requestReply(INSTRUMENT_DETAILS) {
        derivedFields {
            derivedField("IS_USD", BOOLEAN) {
                tradedCurrency == "USD"
            }
        }
    }
}

You can use any logic you would like inside the derivedField codeblock, such as if, switch and so on. Here is a simple example of how to use if inside the derivedField:

requestReplies {
    requestReply(INSTRUMENT_DETAILS) {
        derivedFields {
            derivedField("IS_BUY", BOOLEAN) {
                if (DIRECTION.toString() == "BUY"){
                    true
                } else {
                    false
                }
            }
        }
    }
}

note

Derived fields cannot be used within a where block.

Using an index

The example below uses an index as the request definition. This provides additional indexing at the request level.

requestReplies {
    requestReply(INSTRUMENT_DETAILS) {
        request(INSTRUMENT_DETAILS.BY_INSTRUMENT_ID)
    }
}

Where block

The where block enables you to specify the conditions for which data should be returned. The where block can take two optional parameters:

• row - this represents a row from the table or view
• parameters - this is a GenesisSet that holds the parameters that are passed on the request; the parameters can be accessed by using the GenesisSet getters to access named parameters

In this contrived example below, the where block filters rows whose instrumentCode is not equal to "ALLL3" and the request parameter "ALTERNATE_TYPE" is either "RIC" or "BLOOMBERG".

The row parameter represents the rows returned from the table or view defined at the top of the requestReply definition, in this case, INSTRUMENT_DETAILS.

import Example1 from '/examples/requestserver/_reqrep1.md'

Custom Log messages

import Log from '/snippet/_LOG.md'