Apr 03, 2019 See the following screenshots: The code: Here, dbRef is the database reference to the parent node. The database structure: For each dbRef of different sports, I have a child node “contacts”. I also have a Java class made for the children of “conta.
- When a Firebase client establishes a connection, the Firebase server sends an accurate timestamp to the client so it can use that to correct its incorrect clock when generating push IDs. However, this correction only takes effect once the client has connected to Firebase, so if you generate a push ID before the client connects, we won't make an attempt to correct it.
- The keys (the paths of the new data) are guaranteed to be unique, so there's no point in overwriting them with a numeric key. You can instead set the numeric ID as a child of the object. You can then query objects by that ID child using Firebase Queries.
Key generators are constructed using one of the
getInstance
class methods of this class. KeyGenerator objects are reusable, i.e., after a key has been generated, the same KeyGenerator object can be re-used to generate further keys.
There are two ways to generate a key: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:
![Generate random key in firebase keys 2017 Generate random key in firebase keys 2017](/uploads/1/2/6/0/126089852/537828166.jpg)
- Algorithm-Independent InitializationAll key generators share the concepts of a keysize and a source of randomness. There is an
init
method in this KeyGenerator class that takes these two universally shared types of arguments. There is also one that takes just akeysize
argument, and uses the SecureRandom implementation of the highest-priority installed provider as the source of randomness (or a system-provided source of randomness if none of the installed providers supply a SecureRandom implementation), and one that takes just a source of randomness.Since no other parameters are specified when you call the above algorithm-independentinit
methods, it is up to the provider what to do about the algorithm-specific parameters (if any) to be associated with each of the keys. - Algorithm-Specific InitializationFor situations where a set of algorithm-specific parameters already exists, there are two
init
methods that have anAlgorithmParameterSpec
argument. One also has aSecureRandom
argument, while the other uses the SecureRandom implementation of the highest-priority installed provider as the source of randomness (or a system-provided source of randomness if none of the installed providers supply a SecureRandom implementation).
In case the client does not explicitly initialize the KeyGenerator (via a call to an
init
method), each provider must supply (and document) a default initialization. Every implementation of the Java platform is required to support the following standard
KeyGenerator
algorithms with the keysizes in parentheses: - AES (128)
- DES (56)
- DESede (168)
- HmacSHA1
- HmacSHA256