This project includes the source code of the Lightstreamer Java In-process Adapter API specification. This resource is needed to write Data Adapters and Metadata Adapters for Lightstreamer Server in Java. The adapters will run in process with the Lightstreamer Server. Each Lightstreamer session requires the presence of an Adapter Set, which is made up of one Metadata Adapter and one or multiple Data Adapters. Multiple Adapter Sets can be plugged onto Lightstreamer Server. Please refer to General Concepts document for further details about the role of the Adapters in Lightstreamer.
Each Adapter Set is defined by a configuration file called adapters.xml placed in a specific subfolder of /adapters. Please refer to the WELCOME Adapter Set pre-installed in the factory donwload of Lightstreamer as a reference of Adapters deploy and to the provided template of adapters.xml for a complete description of all the parameters configurable for an Adapter Set.
In case you want to use Eclipse for developing and running your own Adapter Set, please refer to the instructions provided in this thread of our Java Adapter API support forum.
The library is compatible with Lightstreamer Server since 7.4.
For a version of this library compatible with earlier versions of Lightstreamer Server see this tag.
Since the API is available from the Maven Central Repository, to setup your development environment add the following dependency to your pom.xml:
<dependency>
<groupId>com.lightstreamer</groupId>
<artifactId>ls-adapter-inprocess</artifactId>
<version>8.0.0</version>
</dependency>This project includes a simple full implementation of Metadata Adapter in Java, LiteralBasedProvider, made available as sample for inspiration and/or extension.
The LiteralBasedProvider extends the MetadataProviderAdapter abstract class (which in turn implements the MetadataProvider interface). It is used in many Lightstreamer examples and demos, in combination with different Data Adapters and Clients. It is also useful when developing proof of concepts and prototypes, where the main focus is on the Data Adapter.
The following code snippet shows an example of adapters.xml configuration of the LiteralBasedProvider Metadata provider and its properties:
<!-- Mandatory. Define the Metadata Provider. -->
<metadata_provider>
<!-- Mandatory. Java class name of the adapter. -->
<adapter_class>com.lightstreamer.adapters.metadata.LiteralBasedProvider</adapter_class>
<!-- Optional. List of initialization parameters specific for the adapter. -->
<!-- Optional (specific for adapters that inherit from
com.lightstreamer.adapters.metadata.LiteralBasedProvider).
Define values to be returned in getAllowedMaxBandwidth(),
getAllowedMaxItemFrequency(), getAllowedBufferSize() and
getDistinctSnapshotLength() methods, for any User and Item
supplied and optional comma-separated list of User names
to be allowed by the notifyUser() method.
See LiteralBasedProvider javadoc. -->
<!--
<param name="max_bandwidth">40</param>
<param name="max_frequency">3</param>
<param name="buffer_size">30</param>
<param name="distinct_snapshot_length">10</param>
<param name="allowed_users">user123,user456</param>
-->
<!-- Optional (specific for adapters that inherit from
com.lightstreamer.adapters.metadata.LiteralBasedProvider).
Define how the modeMayBeAllowed method should behave, by
associating to each item the modes in which it can be managed
by the Server.
Each triple of parameters of the form "item_family_<n>",
"data_adapter_for_item_family_<n> (optional), and
"modes_for_item_family_<n>" define respectively the item name
pattern (in java.util.regex.Pattern format),
the related Data Adapter, and the allowed
modes (in comma separated format) for a family of items.
Each item is assigned to the first family that matches its name
and (if supplied) the related Data Adapter.
If no families are specified at all, then modeMayBeAllowed
always returns true, though this is not recommended, because
the Server does not support more than one mode out of MERGE,
DISTINCT, and COMMAND for the same item. In such a case, the
Server would just manage each item in the mode specified by the
first Client request it receives for the item and would be up to
the Clients to ensure that the same item cannot be requested in
two conflicting Modes.
See LiteralBasedProvider javadoc. -->
<param name="item_family_1">item.*</param>
<param name="data_adapter_for_item_family_1">MyDataAdapter</param>
<param name="modes_for_item_family_1">MERGE</param>
<!--
<param name="item_family_2">item.*</param>
<param name="modes_for_item_family_2">MERGE,RAW</param>
-->
</metadata_provider>Above, are shown only the specific parameters of LiteralBasedProvider Metadata Adapter. Use the generic template (see the Java In-Process Adapter Interface Project ) as a reference for a complete overview of configuration options.
To build your own version of the Java In-process Adapter library, you have two options: either use Maven (or other build tools) to take care of dependencies and building (recommended) or gather the necessary jars yourself and build it manually. For the sake of simplicity only the Maven case is detailed here.
You can easily build this library using Maven through the pom.xml file located in the root folder of this project. As an alternative, you can use an alternative build tool (e.g. Gradle, Ivy, etc.) by converting the provided pom.xml file.
Assuming Maven is installed and available in your path you can build the library by running
mvn packageFor questions and support please use the Official Forum. The issue list of this page is exclusively for bug reports and feature requests.