This Camel application is intended for use with the Dataspace Connector and the Configuration Manager.
The communication between the Dataspace Connector and data apps can be achieved by using an integration Framework like Apache Camel. This also provides the possibility to use all kinds of different backends for resources registered in the connector, as no separate implementation has to be made for each possible protocol. To keep the Dataspace Connector lightweight and modular, no integration framework will be integrated directly, but rather be executed standalone in parallel to the connector, as can be done with this Camel application.
- Deployment
- Deploying Camel routes
- Defining Camel routes
- Using the Dataspace Connector with SSL enabled
- Using apps
- Contributing
- License
In the following it is described how to build and run the Camel application. If the deployment is successful, the application is available at https://localhost:9090.
To build and run the application with Maven, ensure that at least Java 11 is installed. Then, follow these steps:
- Build the application by executing
mvn clean packagein the application's root directory. - Run the application by executing
java -jar target/dsc-camel-instance-{VERSION}.jar
To build and run the application with Docker, follow these steps:
- Build the application by executing
docker build -t <IMAGE_NAME:TAG> .in the application's root directory. - Run the application by executing
docker run --publish 9090:9090 --detach --name dsc-camel <IMAGE_NAME:TAG>
The docker-compose.yaml sets up the Camel application and a Dataspace Connector. Optionally, other applications like e.g. a database or an MQTT broker can be added to the setup to be used in routes.
- Build the application by executing
docker-compose buildin the application's root directory. - Start the setup by executing
docker-compose up.
This application allows for both defining routes statically before the application is started and adding routes dynamically at runtime.
The easiest way to deploy routes is to statically define them in the Camel Context before the application starts.
Spring will create a default Camel Context on application start. When using that context, all beans and routes you want
to use have to be declared separately/in different locations. By defining a Camel Context in an XML file and importing
that into the application, the whole context including routes and beans can be defined in one place. The file under
src/main/resources/camel-context.xml can be used for defining the Camel context. Inside the camelContext tag,
any number of routes can be added. To import the file into the application, add the following annotation to the main
class:
@ImportResource("classpath:camel-context.xml")
If the Camel context should be loaded from an external file, just change classpath to file in the import statement.
Some Camel components require additional beans to be defined in the application context for a route to be executed (e.g. definition of a data source bean when using the SQL component). These beans can also be defined in camel-context.xml and will then automatically be available for the routes.
Important: the bean tags have to be declared outside the camelContext tag:
<bean id="..." class="..."></bean>
<camelContext id="camelContext" xmlns="http://camel.apache.org/schema/spring">
<route id="...">
...
</route>
</camelContext>
While the static deployment of routes is a simple and quick solution and will probably suffice for testing purposes, in most cases there will be a need to deploy and/or remove routes dynamically at runtime. Therefore, XML files containing routes and, if necessary, required beans can be sent to the application via HTTP using the following endpoints:
- POST /api/routes (multipart/form-data with part file for the XML file): add routes
- DELETE /api/routes/{route-id}: remove routes
- POST /api/beans (multipart/form-data with part file for the XML file): add beans
- DELETE /api/beans/{bean-id}: remove bean
The files sent to the application should have the following structures for routes and beans respectively:
<routes xmlns="http://camel.apache.org/schema/spring">
<route id="...">
...
</route>
</routes>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
<bean id="..." class="...">
...
</bean>
</beans>
Inside the routes and beans tags, any number of routes or beans can be added.
This application uses the Camel Spring XML DSL. Therefore, all Camel routes are defined in XML format. Each route has to be enclosed by route tags and has to contain a start point (<from uri="...">). It can also contain any number of endpoints a message should be sent to (<to uri="...">).
<route id="route-id">
<from uri="..."/>
<to uri="..."/>
</route>
For endpoints, any Camel component can be used (e.g. http, sql). Each component used in the routes has to be added to this application's POM as a dependency. For this, the component's Springboot starter can be used. Hereinafter, example routes are given for using different Camel components as data sources/sinks with the Dataspace Connector. All Camel components used in the examples have already been added to the POM.
The routes described here use version 5 of the Dataspace Connector. They can also be found under
src/main/resources/routes/dsc-v5. The same routes for version 4 of the Dataspace Connector can be found under
src/main/resources/routes/dsc-v4.
The following examples show how to fetch data from different backend systems and publish it to the Dataspace Connector as a resource's data. In all cases, a resource with the specified ID has to be created in the connector first.
The Camel HTTP component cannot be used as a consumer, i.e. it cannot be used in a from tag and thus cannot be used as the start of a route. A simple workaround is to use a timer as the route start and then call the HTTP backend.
<route id="http-to-dsc-example">
<from uri="timer://foo?delay=10000&period=15000"/>
<setHeader name="CamelHttpMethod">
<constant>GET</constant>
</setHeader>
<to uri="http://http-demo-backend:8090/demo"/>
<convertBodyTo type="java.lang.String"/>
<setHeader name="CamelHttpMethod">
<constant>PUT</constant>
</setHeader>
<setHeader name="Authorization">
<constant>Basic YWRtaW46cGFzc3dvcmQ=</constant>
</setHeader>
<to uri="http://dataspace-connector:8080/api/artifacts/927906f2-5ee1-4678-9ace-5f1f2368606c/data"/>
</route>
This route will start every 15 seconds (with an initial delay of 10 seconds), make an HTTP GET call to the backend and send the response to the connector as the data of the artifact with ID 927906f2-5ee1-4678-9ace-5f1f2368606c.
For Spring to be able to load the database driver for the database connection, the dependency of the chosen database management system (e.g. PostgreSQL, MySQL) has to be added to the POM.
When using the Camel SQL component, the database to use has to be configured in a bean. Therefore, add a data source bean:
<bean id="testDataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="url" value="jdbc:postgresql://postgres:5432/testdb"/>
<property name="driverClassName" value="org.postgresql.Driver" />
<property name="username" value="postgres-user" />
<property name="password" value="12345"/>
</bean>
Afterwards, the route definition can be added. The query to use when fetching data from the database has to be specified in the URI of the from tag:
<route id="sql-to-dsc-example">
<from uri="sql:select * from test?initialDelay=10000&delay=15000&useIterator=false&dataSource=#testDataSource"/>
<convertBodyTo type="java.lang.String"/>
<setHeader name="CamelHttpMethod">
<constant>PUT</constant>
</setHeader>
<setHeader name="Authorization">
<constant>Basic YWRtaW46cGFzc3dvcmQ=</constant>
</setHeader>
<to uri="http://dataspace-connector:8080/api/artifacts/927906f2-5ee1-4678-9ace-5f1f2368606c/data"/>
</route>
This route will start every 15 seconds (with an initial delay of 10 seconds), fetch data from the database using the specified query and send that to the connector as the data of the artifact with ID 927906f2-5ee1-4678-9ace-5f1f2368606c.
Note that the data source bean's ID is referenced as the value for the query parameter dataSource in the from tag. This allows you to specify the correct data source if multiple data source beans are defined. There is also a query parameter useIterator which is set to false. This defines that all records returned by the query will be fetched and sent in one message. If the value is set to true, each record returned by the query will be sent in a separate message.
As no Springboot starter is available for the MQTT component, the Paho component is used instead. It also offers support for MQTT, but is, as opposed to the MQTT component, implemented using the Eclipse Paho library. Using the Paho component does not require additional beans to be defined, as all information required for the connection can be given in the URI of the from tag. Therefore, only the route has to added:
<route id="mqtt-to-dsc-example">
<from uri="paho:test-topic?brokerUrl=tcp://mosquitto:1883"/>
<convertBodyTo type="java.lang.String"/>
<setHeader name="CamelHttpMethod">
<constant>PUT</constant>
</setHeader>
<setHeader name="Authorization">
<constant>Basic YWRtaW46cGFzc3dvcmQ=</constant>
</setHeader>
<to uri="http://dataspace-connector:8080/api/artifacts/927906f2-5ee1-4678-9ace-5f1f2368606c/data"/>
</route>
This route will be triggered whenever a new message is published to the topic with name test-topic at the MQTT broker located at tcp://mosquitto:1883 and send that message's payload to the connector as the data of the artifact with ID 927906f2-5ee1-4678-9ace-5f1f2368606c.
The following example shows how to fetch a resource's data from the connector and send it to a backend system.
No additional beans have to be defined to use the file component, so only the route has to be added. As the route starts with fetching data from the connector using HTTP and the Camel HTTP component cannot be used as a consumer, a timer is used as the route start.
<route id="dsc-to-file-example">
<from uri="timer://foo?delay=10000&period=15000"/>
<setHeader name="CamelHttpMethod">
<constant>GET</constant>
</setHeader>
<setHeader name="Authorization">
<constant>Basic YWRtaW46cGFzc3dvcmQ=</constant>
</setHeader>
<to uri="http://dataspace-connector:8080/api/artifacts/927906f2-5ee1-4678-9ace-5f1f2368606c/data"/>
<convertBodyTo type="java.lang.String"/>
<to uri="file:/output?fileName=resourcedata.txt"/>
</route>
This route will start every 15 seconds (with an initial delay of 10 seconds), fetch the data of the connector's artifact with ID 927906f2-5ee1-4678-9ace-5f1f2368606c and write it to a file located at /output/resourcedata.txt.
In all given example routes the Dataspace Connector is addressed using HTTP, not HTTPS. This is due to the fact that in test environments self-signed certificates are often used. These lead to an error when Camel tries to call the connector.
To be able to use the connector with SSL enabled also when using self-signed certificates, an implementation of the
org.apache.camel.component.http.HttpClientConfigurer that works with self-signed certificates has been added to this
project (src/main/java/de/fraunhofer/isst/dataspaceconnector/camel/util/SelfSignedHttpClientConfigurer). Note that
this disables the hostname verification and thus is not secure! To use this HttpClientConfigurer in routes, declare
it as a bean and add it as a query parameter at the end of the connector URI:
uri="https://dataspace-connector:8080/...?httpClientConfigurer=#idOfHttpClientConfigurerBean"/>
In productive environments SSL should always be enabled and real certificates should be used!
When using Camel, data apps can be integrated into the routes. In the following, it will be described how to achieve this. If possible, a data app should provide one HTTP endpoint for both input and output. The data transferred in a route can therefore be sent to this endpoint using the Camel HTTP component. The app's result will then be synchronously returned as the response. Besides the actual data, an app may also require information about the usage policy associated with this data to be able to enforce usage control. To not be bound to a specific payload format, this additional information is not sent as part of the payload, but rather added in HTTP headers. Thus, it is still sent in the same request as the corresponding data, but is clearly separated from it. Camel offers the possibility to set Camel headers for a message, that in case of communicating via HTTP will be mapped to HTTP headers once an endpoint is called. The Camel headers can therefore be used for setting the additional information.
The additional headers for calling a data app are:
- TargetDataUri: URI of the artifact that is being transferred
- ContractId: ID of the contract associated with the transferred artifact
- AppName: name of the app the message is sent to
- AppUri: URI of the app the message is sent to
Based on this, a route that includes a data app looks as follows:
<route id="backend-to-app-to-dsc-example">
<from uri="timer://foo?delay=10000&period=20000"/>
<setHeader name="CamelHttpMethod">
<constant>GET</constant>
</setHeader>
<to uri="http://http-demo-backend:8090/demo"/>
<convertBodyTo type="java.lang.String"/>
<setHeader name="TargetDataUri">
<constant>
http://dataspace-connector:8080/api/artifacts/927906f2-5ee1-4678-9ace-5f1f2368606c
</constant>
</setHeader>
<setHeader name="ContractId">
<constant>
http://dataspace-connector:8080/api/agreements/533012aa-25d4-49fe-a3e1-56aa37777b52
</constant>
</setHeader>
<setHeader name="AppName">
<constant>Demo App</constant>
</setHeader>
<setHeader name="AppUri">
<constant>http://demo-app:5000</constant>
</setHeader>
<setHeader name="CamelHttpMethod">
<constant>POST</constant>
</setHeader>
<to uri="http://demo-app:5000?socketTimeout=10000"/>
<setHeader name="CamelHttpMethod">
<constant>PUT</constant>
</setHeader>
<setHeader name="Authorization">
<constant>Basic YWRtaW46cGFzc3dvcmQ=</constant>
</setHeader>
<to uri="http://dataspace-connector:8080/api/artifacts/927906f2-5ee1-4678-9ace-5f1f2368606c/data"/>
</route>
This example route fetches data from an HTTP backend, sets the usage control relevant headers using the setHeader tag and then sends the data and the headers to a data app. The response returned by the app is sent to the Dataspace Connector as the data of an existing resource.
You are very welcome to contribute to this project when you find a bug, want to suggest an improvement, or have an idea for a useful feature. Please find a set of guidelines at the CONTRIBUTING.md and the CODE_OF_CONDUCT.md.
This project is licensed under the Apache License 2.0 - see the LICENSE for details.
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