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Pre-Processing/Post-Processing Services with Mashups

Pre-processing and post-processing for services commonly involves tasks such as decoding encrypted data, encrypting data, decompressing or compressing data, filtering data or data scrubbing. You can handle these types of requirements with a mashup that uses scripting to invoke pre- or post-processing code.

Tip: it is a good practice to design pre- or post-processing code as its own service that can be invoked by many mashups.

Pre-processing Mashup

To implement pre-processing you must:

  1. Write the logic to handle pre-processing as a Java class or use Java libraries, as needed.

  2. Add the custom Java classes to the classpath for the EMML Reference Runtime Engine. Copy them to the web-apps-home/emml/WEB-INF/classes folder or add them in a JAR to the web-apps-home/emml/WEB-INF/lib folder.

  3. Restart the EMML Engine.

  4. Create a mashup script with the following components:

    1. <input> variables, as needed, to receive the data to be pre-processed and an <output> variable for the result. For example:

      ... 
<operation name="getreviews"> 
  <input name="userId" type="string" default="someone@myOrg.com" /> 
  <input name="accessId" type="string" 
    default="xOtPy9Sy7JCI3Y8aNqEkZBxmkPQw/ZH8"/> 
  <output name="result" type="string"/>

    2. Add a <script> statement to call the pre-processing logic.

      This example uses JavaScript scripting and shows an encryption class that decrypts the accessId input parameter. To call the pre-processing logic in JavaScript, you must use fully qualified class names starting with the Packages keyword.

      ... 
  <output name="result" type="string" inputvariables="$accessId" 
    outputvariable="$accessId"/> 
  <script type="text/javascript"> 
    <![CDATA[ 
      var encrypter = new 
        Packages.com.myOrg.services.Encrypter("My Pass Phrase!") 
      accessId = encrypter.decrypt(accessId); 
    ]]> 
  </script>

    3. Invoke the service with the pre-processed data. For example: 

      ... 
  </script> 
  <directinvoke 
    endpoint="http://ecs.amazonaws.com/onca/xml?Service=AWSECommerceService" 
    method="GET" 
    AWSAccessKeyId="$accessId" 
    Version="2009-01-15" 
    Operation="ListSearch" 
    ListType="WishList" 
    Email="some.body@my.company.com" 
    outputvariable="$result"/>

Post-processing Mashup

At its simplest, any mashup that invokes a service and performs an action using the result is providing service post-processing. To implement post-processing logic that is directly provided by mashup script statements, you must:

  1. Write the logic to handle the post-processing as a Java class or use Java libraries, as needed.

  2. Add the custom Java classes to the classpath for the EMML Reference Runtime Engine. Copy them to the web-apps-home/emml/WEB-INF/classes folder or add them in a JAR to the web-apps-home/emml/WEB-INF/lib folder.

  3. Restart the EMML Engine.

  4. Create a mashup script with the following components:

    1. <variable>s , as needed, to receive the results from the service or other data to be post-processed and an <output> variable for the result. For example:

      ... 
<operation name="encryptResult"> 
  <variable name="svcResult" type="document"/> 
  <output name="result" type="string"/>

    2. Invoke the service. For example: 

      ... 
  <output name="result" type="string"/> 
  <directinvoke 
    endpoint="http://ecs.amazonaws.com/onca/xml?Service=AWSECommerceService" 
    method="GET" 
    AWSAccessKeyId="xOtPy9Sy7JCI3Y8aNqEkZBxmkPQw/ZH8" 
    Version="2009-01-15" 
    Operation="ListSearch" 
    ListType="WishList" 
    Email="some.body@my.company.com" 
    outputvariable="$svcResult"/> 
  <filter /> 
  <constructor outputvariable="$svcResult"> 
    <ns:mylist>{$svcResult/ns:ListSearchResponse/ns:Lists/ns:List}</ns:mylist> 
  </constructor>

  5. Add a <script> statement to call the post-processing logic.

    This example uses JavaScript scripting. It shows an encryption class that encrypts the filtered and constructed results from the service. To call the post-processing logic in JavaScript, you must use fully qualified class names starting with the Packages keyword.

    ... 
  </constructor> 
  <script type="text/javascript" inputvariables="$svcResult" 
    outputvariable="$result"> 
    <![CDATA[ 
      var encrypter = new 
        Packages.com.myOrg.services.Encrypter("My Pass Phrase!") 
      result = encrypter.encrypt(svcResult); 
    ]]> 
  </script> 
...