Detailed Feedback

HTTP JSON API Service¶

WARNING: the HTTP JSON API described in this document is actively being designed and is subject to breaking changes, including all request and response elements demonstrated below or otherwise implemented by the API. We welcome feedback about the API on our issue tracker or on Slack.

The JSON API provides a significantly simpler way than the Ledger API to access basic active contract set functionality:

creating contracts,
exercising choices on contracts, and
querying the current active contract set.

The goal is to get you up and running writing effective ledger-integrated applications quickly, so we have deliberately excluded complicating concerns, including but not limited to

inspecting transactions,
asynchronous submit/completion workflows,
temporal queries (e.g. active contracts as of a certain time), and
ledger metaprogramming (e.g. packages and templates).

For these and other features, use the Ledger API instead.

How to start¶

Start sandbox from a DAML project directory¶

$ daml sandbox --wall-clock-time --ledgerid MyLedger ./.daml/dist/quickstart-0.0.1.dar

Start HTTP service from a DAML project directory¶

$ daml json-api --ledger-host localhost --ledger-port 6865 \
    --http-port 7575 --max-inbound-message-size 4194304 --package-reload-interval 5s \
    --application-id HTTP-JSON-API-Gateway --static-content "prefix=static,directory=./static-content" \
    --query-store-jdbc-config "driver=org.postgresql.Driver,url=jdbc:postgresql://localhost:5432/test?&ssl=true,user=postgres,password=password,createSchema=false"

$ daml json-api --help
HTTP JSON API daemon
Usage: http-json-binary [options]

  --help
        Print this usage text
  --ledger-host <value>
        Ledger host name or IP address
  --ledger-port <value>
        Ledger port number
  --address <value>
        IP address that HTTP JSON API service listens on. Defaults to 0.0.0.0.
  --http-port <value>
        HTTP JSON API service port number
  --application-id <value>
        Optional application ID to use for ledger registration. Defaults to HTTP-JSON-API-Gateway
  --package-reload-interval <value>
        Optional interval to poll for package updates. Examples: 500ms, 5s, 10min, 1h, 1d. Defaults to 5 seconds
  --max-inbound-message-size <value>
        Optional max inbound message size in bytes. Defaults to 4194304
  --query-store-jdbc-config "driver=<JDBC driver class name>,url=<JDBC connection url>,user=<user>,password=<password>,createSchema=<true|false>"
        Optional query store JDBC configuration string. Contains comma-separated key-value pairs. Where:
        driver -- JDBC driver class name,
        url -- JDBC connection URL,
        user -- database user name,
        password -- database user password
        createSchema -- boolean flag, if set to true, the process will re-create database schema and terminate immediately.
        Example: "driver=org.postgresql.Driver,url=jdbc:postgresql://localhost:5432/test?&ssl=true,user=postgres,password=password,createSchema=false"
  --static-content "prefix=<URL prefix>,directory=<directory>"
        DEV MODE ONLY (not recommended for production). Optional static content configuration string. Contains comma-separated key-value pairs. Where:
        prefix -- URL prefix,
        directory -- local directory that will be mapped to the URL prefix.
        Example: "prefix=static,directory=./static-content"
  --access-token-file <value>
    provide the path from which the access token will be read, required to interact with an authenticated ledger, no default

With Authentication¶

Apart from interacting with the Ledger API on behalf of the user, the HTTP JSON API server must also interact with the Ledger API to maintain some relevant internal state.

For this reason, you must provide an access token when you start the HTTP JSON API if you’re running it against a Ledger API server that requires authentication.

Note that this token is used exclusively for maintaining the internal list of known packages and templates, and that it will not be use to authenticate client calls to the HTTP JSON API: the user is expected to provide a valid authentication token with each call.

The HTTP JSON API servers requires no access to party-specific data, only access to the ledger identity and package services: a token issued for the HTTP JSON API server should contain enough claims to contact these two services but no more than that. Please refer to your ledger operator’s documentation to find out how.

Once you have retrieved your access token, you can provide it to the HTTP JSON API by storing it in a file and provide the path to it using the --access-token-file command line option.

If the token cannot be read from the provided path or the Ledger API reports an authentication error (for example due to token expiration), the HTTP JSON API will report the error via logging. The token file can be updated with a valid token and it will be picked up at the next attempt to send a request.

Example session¶

$ daml new iou-quickstart-java quickstart-java
$ cd iou-quickstart-java/
$ daml build
$ daml sandbox --wall-clock-time --ledgerid MyLedger ./.daml/dist/quickstart-0.0.1.dar
$ daml json-api --ledger-host localhost --ledger-port 6865 --http-port 7575

Choosing a party¶

You specify your party and other settings with JWT. In testing environments, you can use https://jwt.io to generate your token.

The default “header” is fine. Under “Payload”, fill in:

{
  "ledgerId": "MyLedger",
  "applicationId": "foobar",
  "party": "Alice"
}

Keep in mind: - the value of ledgerId payload field has to match --ledgerid passed to the sandbox. - you can replace Alice with whatever party you want to use.

Under “Verify Signature”, put secret as the secret (_not_ base64 encoded); that is the hardcoded secret for testing.

Then the “Encoded” box should have your token; set HTTP header Authorization: Bearer copy-paste-token-here.

Here are two tokens you can use for testing:

{"ledgerId": "MyLedger", "applicationId": "foobar", "party": "Alice"} eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJsZWRnZXJJZCI6Ik15TGVkZ2VyIiwiYXBwbGljYXRpb25JZCI6ImZvb2JhciIsInBhcnR5IjoiQWxpY2UifQ.4HYfzjlYr1ApUDot0a6a4zB49zS_jrwRUOCkAiPMqo0
{"ledgerId": "MyLedger", "applicationId": "foobar", "party": "Bob"} eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJsZWRnZXJJZCI6Ik15TGVkZ2VyIiwiYXBwbGljYXRpb25JZCI6ImZvb2JhciIsInBhcnR5IjoiQm9iIn0.2LE3fAvUzLx495JWpuSzHye9YaH3Ddt4d2Pj0L1jSjA

For production use, we have a tool in development for generating proper RSA-encrypted tokens locally, which will arrive when the service also supports such tokens.

GET http://localhost:7575/contracts/search ¶

POST http://localhost:7575/contracts/search ¶

List currently active contracts that match a given query.

application/json body, formatted according to the /contracts/search query language:

{"%templates": [{"moduleName": "Iou", "entityName": "Iou"}],
 "amount": 999.99}

empty output:

{
    "status": 200,
    "result": []
}

output, each contract formatted according to DAML-LF JSON Encoding:

{
    "status": 200,
    "result": [
        {
            "observers": [],
            "agreementText": "",
            "signatories": [
                "Alice"
            ],
            "contractId": "#489:0",
            "templateId": {
                "packageId": "ac3a64908d9f6b4453329b3d7d8ddea44c83f4f5469de5f7ae19158c69bf8473",
                "moduleName": "Iou",
                "entityName": "Iou"
            },
            "witnessParties": [
                "Alice"
            ],
            "argument": {
                "observers": [],
                "issuer": "Alice",
                "amount": "999.99",
                "currency": "USD",
                "owner": "Alice"
            }
        }
    ]
}

POST http://localhost:7575/command/create ¶

Create a contract.

application/json body, argument formatted according to DAML-LF JSON Encoding:

{
  "templateId": {
    "moduleName": "Iou",
    "entityName": "Iou"
 },
  "argument": {
    "observers": [],
    "issuer": "Alice",
    "amount": "999.99",
    "currency": "USD",
    "owner": "Alice"
  }
}

output:

{
    "status": 200,
    "result": {
        "observers": [],
        "agreementText": "",
        "signatories": [
            "Alice"
        ],
        "contractId": "#56:0",
        "templateId": {
            "packageId": "ac3a64908d9f6b4453329b3d7d8ddea44c83f4f5469de5f7ae19158c69bf8473",
            "moduleName": "Iou",
            "entityName": "Iou"
        },
        "witnessParties": [
            "Alice"
        ],
        "argument": {
            "observers": [],
            "issuer": "Alice",
            "amount": "999.99",
            "currency": "USD",
            "owner": "Alice"
        }
    }
}

POST http://localhost:7575/command/exercise ¶

Exercise a choice on a contract.

"contractId": "#56:0" is the value from the create output application/json body:

{
    "templateId": {
        "moduleName": "Iou",
        "entityName": "Iou"
    },
    "contractId": "#56:0",
    "choice": "Iou_Transfer",
    "argument": {
        "newOwner": "Alice"
    }
}

output:

{
    "status": 200,
    "result": [
        {
            "archived": {
                "contractId": "#56:0",
                "templateId": {
                    "packageId": "ac3a64908d9f6b4453329b3d7d8ddea44c83f4f5469de5f7ae19158c69bf8473",
                    "moduleName": "Iou",
                    "entityName": "Iou"
                },
                "witnessParties": [
                    "Alice"
                ]
            }
        },
        {
            "created": {
                "observers": [],
                "agreementText": "",
                "signatories": [
                    "Alice"
                ],
                "contractId": "#301:1",
                "templateId": {
                    "packageId": "ac3a64908d9f6b4453329b3d7d8ddea44c83f4f5469de5f7ae19158c69bf8473",
                    "moduleName": "Iou",
                    "entityName": "IouTransfer"
                },
                "witnessParties": [
                    "Alice"
                ],
                "argument": {
                    "iou": {
                        "observers": [],
                        "issuer": "Alice",
                        "amount": "999.99",
                        "currency": "USD",
                        "owner": "Alice"
                    },
                    "newOwner": "Alice"
                }
            }
        }
    ]
}

GET http://localhost:7575/parties ¶

output:

{
    "status": 200,
    "result": [
        {
            "party": "Alice",
            "isLocal": true
        }
    ]
}

HTTP JSON API Service¶

How to start¶

Start sandbox from a DAML project directory¶

Start HTTP service from a DAML project directory¶

With Authentication¶

Example session¶

Choosing a party¶

GET http://localhost:7575/contracts/search¶

POST http://localhost:7575/contracts/search¶

POST http://localhost:7575/command/create¶

POST http://localhost:7575/command/exercise¶

GET http://localhost:7575/parties¶

GET http://localhost:7575/contracts/search ¶

POST http://localhost:7575/contracts/search ¶

POST http://localhost:7575/command/create ¶

POST http://localhost:7575/command/exercise ¶

GET http://localhost:7575/parties ¶