loopback-connector-soap

The SOAP connector enables LoopBack applications to interact with SOAP-based web services described using WSDL.

Installation

In your application root directory, enter:

$ npm install loopback-connector-soap --save

This will install the module from npm and add it as a dependency to the application's  package.json file.

Overview

There are two ways to use the SOAP connector:

• Use the LoopBack CLI lb soap command to automatically create a set of models based on a SOAP service WSDL file. Often, this will be the easiest way to connect to a SOAP web service, but may not be suitable for all applications. For more information, see SOAP generator.
• Write the code manually, calling the loopback-connector-soap and data source APIs directly. This is the approach illustrated here.

While both approaches use the loopback-connector-soap data source connector, they appear quite different.

SOAP data source properties

The following table describes the SOAP data source properties you can set in datasources.json.

operations property

The operations property value is a JSON object that has a property (key) for each method being defined for the model. The corresponding value is an object with the following properties:

| Property | Type | Description | |---|---|---| | service | String | WSDL service name | | port | String | WSDL port name | | operation | String | WSDL operation name |

Here is an example operations property for the periodic table service:

operations: {
  // The key is the method name
  periodicTable: {
    service: 'periodictable', // The WSDL service name
    port: 'periodictableSoap', // The WSDL port name
    operation: 'GetAtomicNumber' // The WSDL operation name
  }
}

IMPORTANT: When using the CLI data source generator, you must supply the "stringified JSON" value for this property. For example:

{"getAtomicWeight":{"service":"periodictable","port":"periodictableSoap","operation":"GetAtomicWeight"},"getAtomicNumber":{"service":"periodictable","port":"periodictableSoap","operation":"GetAtomicNumber"}}

To generate the stringified value, you can use the following code (for example):

var operations = {
  "operations": {
    "getAtomicWeight": {
      "service": "periodictable",
      "port": "periodictableSoap",
      "operation": "GetAtomicWeight"
    },
    "getAtomicNumber": {
      "service": "periodictable",
      "port": "periodictableSoap",
      "operation": "GetAtomicNumber"
    }
  }
};

var stringifiedOps = JSON.stringify (operations);
console.log(stringifiedOps);

security property

The security property value is a JSON object with a scheme property. The other properties of the object depend on the value of scheme. For example:

security: {
    scheme: 'WS',
    username: 'test',
    password: 'testpass',
    passwordType: 'PasswordDigest'
}

1 currently unsupported, use "wsdl_headers": { "Authorization": "Basic …" }, instead, details: issue #92.

Creating a model from a SOAP data source

Instead of defining a data source with datasources.json, you can define a data source in code; for example:

ds.once('connected', function () {

  // Create the model
  var PeriodictableService = ds.createModel('PeriodictableService', {});

  // External PeriodTable WebService operation exposed as REST APIs through LoopBack
  PeriodictableService.atomicnumber = function (elementName, cb) {
    PeriodictableService.GetAtomicNumber({ElementName: elementName || 'Copper'}, function (err, response) {
      var result = response;
      cb(err, result);
    });
  };
...
}

Extending a model to wrap and mediate SOAP operations

You can extend a LoopBack model to wrap or mediate SOAP operations and define new methods. The following example simplifies the GetAtomicNumber operation:

periodictableperiodictableSoap.GetAtomicNumber = function(GetAtomicNumber, callback) {
    periodictableperiodictableSoap.GetAtomicNumber(GetAtomicNumber, function (err, response) {
      var result = response;
      callback(err, result);
    });
}

Creating a model from a SOAP data source

The SOAP connector loads WSDL documents asynchronously. As a result, the data source won't be ready to create models until it's connected. The recommended way is to use an event handler for the 'connected' event; for example as shown below.

Once you define the model, you can extend it to wrap or mediate SOAP operations and define new methods. The example below shows adding a LoopBack remote method for the SOAP service's GetAtomicNumber operation.

...
ds.once('connected', function () {

  // Create the model
  var PeriodictableService = ds.createModel('PeriodictableService', {});

  // External PeriodTable WebService operation exposed as REST APIs through LoopBack
  PeriodictableService.atomicnumber = function (elementName, cb) {
    PeriodictableService.GetAtomicNumber({ElementName: elementName || 'Copper'}, function (err, response) {
      var result = response;
      cb(err, result);
    });
  };

  // Map to REST/HTTP
  loopback.remoteMethod(
      PeriodictableService.atomicnumber, {
        accepts: [
          {arg: 'elementName', type: 'string', required: true,
            http: {source: 'query'}}
        ],
        returns: {arg: 'result', type: 'object', root: true},
        http: {verb: 'get', path: '/GetAtomicNumber'}
      }
  );
})
...

Example

For a complete example using the LoopBack SOAP connector in LoopBack 4, see SOAP calculator tutorial.