This documentation applies to older versions of WSO2 ESB connectors. To find the documentation relevant to the version you are using, select the connector from the WSO2 Connector Store and click Documentation.

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This section walks you through the basic structure of a connector and describes 

Creating the Maven project template

Execute the following command in your Command Line Interface (CLI), to generate an Apache Maven project for a sample connector code using an Maven archetype.

You may need to give a name for the connector while processing the above. E.g. you can give HelloWorldConnector as the connector name.

mvn archetype:generate -DarchetypeGroupId=org.wso2.carbon.extension.archetype -DarchetypeArtifactId=org.wso2.carbon.extension.archetype.esb.connector-archetype -DarchetypeVersion=1.0.0  -DgroupId=org.wso2.carbon.esb.connector -DartifactId=org.wso2.carbon.esb.connector.test -Dversion=1.0.0 -DarchetypeRepository=http://maven.wso2.org/nexus/content/repositories/wso2-public/

This creates the org.wso2.carbon.esb.connector.test/ directory in the current location of your machine, with a directory structure similar to the following:

folder structure of a connector

The directory structure includes the following files and directories.

pom.xmlThis contains the required dependencies for the connector core libraries, relevant Synapse libraries, and Maven repositories for a specific connector.
/assemble-connector.xml/filter.propertiesThese files are used at the connector build time. You do not need to modify this file.
/HelloWorld.javaThis is required for integration tests of JAVA-based connectors. For information on editing it, see the example given below.
/resources/config/component.xmlThis is included in each module, and defines the available methods in the module.
/init.xmlThis is mandatory for every connector. Use this to initialize the connector environment. For example, when writing the Salesforce connector, include the login call here. You can store the Sessiontoken and API URL returned as the response, in a property and use with other operations.
/connector.xmlThis defines the connector name and dependent modules. (i.e. the metadata of the connector)
/HelloWorld-template.xmlThis is the actual API operation calling configuration including the Synapse template of the sequence. This contains the steps necessary to call the API that is exposed by the third party. Each method of the API can be written in a manner similar to init.xml. If there is any Java code, the code should be included under Java (e.g. HelloWorld.java file), and the relevant dependencies should be added to pom.xml

After creating the Maven project template, import it to an IDE, and edit the following files.

Editing the connector.xml file

This is the main component of the ESB connector, which contains the metadata of the connector. You can add any number of resources (referred to as components) inside the resource/ directory, and include all available resources, in this connector.xml file as dependencies, to load all methods implemented in those components. Following is a sample connector.xml file.

<connector>
   <component name="twitter" package="org.wso2.carbon.connectors">
       <dependency component="twitter-config"/>
       <dependency component="twitter-search"/>
       <description>synapse library for twitter connector</description>
   </component>
   <icon>icon/icon-twitter-small.png</icon>
</connector>

The properties of the above connector.xml file are described below.

PropertyDescription
name

A name for the connector. This connector name should be unique, as the connector methods will refer the connector using this as shown in the following example:
<twitter.getSearchTweets>...</twitter.getSearchTweets>

packageThe Java package, from which connectors are implemented.
componentThe resources that are available inside the resources/ directory of the folder structure.
dependency

Each dependency points to each resource/component. It will be used to load all methods implemented in the resource into the ESB.

The component property denotes the name of the resource/component. For example, "twitter-search" is the resource name of the following dependency.
<dependency component="twitter-search"/>

iconRelative path of the connector icon.

Editing the component.xml file

This file defines the metadata of the component. You can add any number of components inside the resource/ directory, and each component can have multiple methods. You need to define all methods implemented in a component in the component.xml file as sub-components, as shown in the example below.

<component name="twitter-search" type="synapse/template">
   <subComponents>
       <component name="getSearchTweets">
           <file>getSearchTweets.xml</file>
           <description>
               Returns a collection of relevant Tweets matching a specified query.
           </description>
       </component>
       <component name="getSavedSearchesList">
           <file>getSavedSearchesList.xml</file>
           <description>Returns the authenticated user’s saved search queries.</description>
       </component>
   </subComponents>
</component>

The properties of the above connector.xml file are described below.

PropertyDescription
name

A name for the resource/component.

type 
subComponentsAll the methods implemented in a component.
component name

The name of the method (i.e. ideally a sequence template).

fileThe name of the method file with the extension.
description

A brief description about the functionality of the method.

Editing the sample Synapse template (HelloWorld-template.xml file)

You need to edit the HelloWorld-template.xml file to include the Synapse configuration for the methods as shown in the example below.

<template xmlns="http://ws.apache.org/ns/synapse" name="helloworldconnector-operation">
    <parameter name="HostAddress"/>
    <sequence>
        <log level="full">
            <property name="HostAddress" expression="$func:HostAddress" />
        </log>
        <class name="org.wso2.carbon.connector.HelloWorldConnector" />
    </sequence>
</template>

Sample HelloWorld.java file

A sample configuration you can use for integration testing of JAVA-based connectors is shown below.

/*
*  Copyright (c) 2005-2010, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
*
*  WSO2 Inc. licenses this file to you under the Apache License,
*  Version 2.0 (the "License"); you may not use this file except
*  in compliance with the License.
*  You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.wso2.carbon.connector;

import org.apache.abdera.Abdera;
import org.apache.abdera.model.Document;
import org.apache.abdera.protocol.client.AbderaClient;
import org.apache.synapse.MessageContext;
import org.wso2.carbon.connector.core.*;
import org.apache.abdera.model.Entry;

public class HelloWorldConnector extends AbstractConnector {

    Abdera abdera;
    AbderaClient abderaClient;

    Document<Entry> doc;
    String HostAddress;

    public void connect(MessageContext messageContext) throws ConnectException {

        try {
            /**
             * Add your connector code here
             */
            HostAddress = getParameter(messageContext, "HostAddress").toString();
            abdera = new Abdera();
            abderaClient = new AbderaClient(abdera);

                // Get the Entry from Server
                doc = abderaClient.get(HostAddress).getDocument();

        log.info(doc.getRoot());
        } catch (Exception e) {
            throw new ConnectException(e);
        }
    }
}

 

Adding dependencies

 

Add the following code to the pom.xml file, to add dependencies.

 

<dependencies>
    <dependency>
        <groupId>org.apache.synapse</groupId>
        <artifactId>synapse-core</artifactId>
        <version>2.1.7-wso2v3-SNAPSHOT</version>
    </dependency>
    <dependency>
        <groupId>org.wso2.carbon</groupId>
        <artifactId>org.wso2.carbon.mediation.library.connectors.core</artifactId>
        <version>4.1.0</version>
    </dependency>
</dependencies>
<pluginRepositories>
    <pluginRepository>
        <id>wso2.releases</id>
        <name>WSO2 internal Repository</name>
        <url>http://maven.wso2.org/nexus/content/repositories/releases/</url>
        <releases>
            <enabled>true</enabled>
            <updatePolicy>daily</updatePolicy>
            <checksumPolicy>ignore</checksumPolicy>
        </releases>
    </pluginRepository>
    <pluginRepository>
        <id>wso2.snapshots</id>
        <name>Apache Snapshot Repository</name>
        <url>http://maven.wso2.org/nexus/content/repositories/snapshots/</url>
        <snapshots>
            <enabled>true</enabled>
            <updatePolicy>daily</updatePolicy>
        </snapshots>
        <releases>
            <enabled>false</enabled>
        </releases>
    </pluginRepository>
    <pluginRepository>
        <id>wso2-nexus</id>
        <name>WSO2 internal Repository</name>
        <url>http://maven.wso2.org/nexus/content/groups/wso2-public/</url>
        <releases>
            <enabled>true</enabled>
            <updatePolicy>daily</updatePolicy>
            <checksumPolicy>ignore</checksumPolicy>
        </releases>
    </pluginRepository>
</pluginRepositories>
<repositories>
    <repository>
        <id>wso2-nexus</id>
        <name>WSO2 internal Repository</name>
        <url>http://maven.wso2.org/nexus/content/groups/wso2-public/</url>
        <releases>
            <enabled>true</enabled>
            <updatePolicy>daily</updatePolicy>
            <checksumPolicy>ignore</checksumPolicy>
        </releases>
    </repository>
    <repository>
        <id>wso2.releases</id>
        <name>WSO2 internal Repository</name>
        <url>http://maven.wso2.org/nexus/content/repositories/releases/</url>
        <releases>
            <enabled>true</enabled>
            <updatePolicy>daily</updatePolicy>
            <checksumPolicy>ignore</checksumPolicy>
        </releases>
    </repository>
    <repository>
        <id>wso2.snapshots</id>
        <name>Apache Snapshot Repository</name>
        <url>http://maven.wso2.org/nexus/content/repositories/snapshots/</url>
        <snapshots>
            <enabled>true</enabled>
            <updatePolicy>daily</updatePolicy>
        </snapshots>
        <releases>
            <enabled>false</enabled>
        </releases>
    </repository>
</repositories>

Building the connector

Navigate to the org.wso2.carbon.esb.connector.test/ directory using your CLI, and execute the following command to build the connector you created above: maven clean install

Now that you understand the basic structure of a connector, you can start writing your own connector, which can either be a soap-based connector, REST-based connector or a JAVA API-based connector. For more information on how you can write your own connector based on the API you have decided to use, see Connector Types.

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