Query User Information

To query a credential associated with a user, we need to use a user administration transaction context. The GetUser() method in the UsersTxContext retrieves a given user from the user database.

type UsersTxContext interface {
    .
    ...
    // GetUser obtain user's record from database
    GetUser(userID string) (*types.User, error)
    ...
    .
}

prerequisite

For the example shown here to work, we need to have

• Two databases named db1 and db2 in the Orion server. If you have not created these two databases, refer to creates databases using SDK to create db1 and db2.
• Two users named alice and bob. If you have not created these users already, refer to create users using SDK.

Finally, Create a connection and Open a database session.

Source Code

package main

import (
    "fmt"
    "strconv"
)

func main() {
    bcdb, err := createConnection()
    // if err is not nil, print and return

    session, err := openSession(bcdb)
    // if err is not nil, print and return

    tx, err := session.UsersTx()
    // if err is not nil, print and return

    alice, err := tx.GetUser("alice")
    // if err is not nil, print and return

    err = dbtx.Abort()
    // if err is not nil, print and return
}

Source Code Commentary

For the sake of simplicity, not all errors are handled in this code. Further, the implementation of createConnection() and openSession() can be found here.

Calling session.UsersTx() starts a new user administration transaction and returns the user administration transaction context. We can then query credentials using this transaction context.

Calling GetUser("alice") fetches the alice credentials from the Orion server. The structure of the returned user is shown below:

type User struct {
    Id                   string
    Certificate          []byte
    Privilege            *Privilege
}

type Privilege struct {
    DbPermission map[string]Privilege_Access
    // admin has privileges to submit a user administration transaction,
    // cluster configuration transaction, and database administration
    // transaction. Further, admin has permission to read-write states
    // from any database provided that the state has no ACL defined. If
    // a state has a read and write ACL, the admin can read or write to
    // the state only if the admin is listed in the read or write ACL list.
    Admin                bool
}