signal4j

A facade to make using the libsignal-service easy

Installation

You have to have the JCE Unlimited Strength Policy Files installed if you are using the Oracle JRE.

Gradle

repositories {
    mavenCentral()
}

dependencies {
    compile 'com.github.turakar:signal4j:1.0.0'
}

Maven

<dependency>
  <groupId>com.github.turakar</groupId>
  <artifactId>signal4j</artifactId>
  <version>1.0.0</version>
</dependency>

Usage

Central part of the library is the SignalService class.

Storage

The library stores all your keys and metadata (not messages themself) inside the store store.json. The store is managed and saved on any changes by the library. To reset the state delete the store file. The saved contacts and groups are updated automatically on incoming messages.

Register

You can register as primary or secondary (provisioned) device using the methods startConnectAsPrimary(), finishConnectAsPrimary(), startConnectAsSecondary(), finishConnectAsSecondary(). See the javadoc for further details on this. You only have to do this at install time. Do not do this again without deleting the store file.

PreKeys

PreKeys are used for encryption and have to be generated prior to using them. Therefore you can use checkPreKeys() which has to be called regularly.

Sync

You can request a sync message (containing contacts, groups and blocked list) using requestSync(). This will populate the store file.

Sending Messages

Messages are represented by SignalServiceDataMessage. You can either create them using the constructors or using the builder. Attachments should be sent as SignalServiceAttachmentStream. To send a message use sendMessage().

Receiving Messages

Receiving is done using pull() which is a blocking operation. Messages are processed using ConversationListener which has to be added prior to calling pull() using addConversationListener(). The ConversationListener receives all data messages through onMessage() (even the ones of another device of you) while associating User objects automatically to the sender's phone number. It additionally receives sync updates (those from requestSync() too) through onContactUpdate() and onGroupUpdate(). Using onReadUpdate() you can get read notifications from a different device of you. You cannot send read notifications yourself in the moment (WIP). Remember that read notifications are not transmitted to your contacts but only to the devices you use to manage notifications.

Downloading attachments

You can download attachments using saveAttachment(). The attachments are saved to the folder attachments and you get a File object pointing at it. There are convenience methods for getting a saved attachment (getAttachment()) and deleting a saved attachment (deleteAttachment()). The avatars of contacts and groups are downloaded automatically with the sync messages and therefore should be retrieved only using getAttachment(). Old avatars are automatically deleted once a new avatar arrives.

Turakar/signal4j