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| |
| <document> |
| <properties> |
| <title>Apache Synapse - Sample 8</title> |
| </properties> |
| <body> |
| <section name="Sample 8: Introduction to Static and Dynamic Registry Resources, and Using XSLT Transformations"> |
| <div class="xmlConf"><definitions xmlns="http://ws.apache.org/ns/synapse"> |
| |
| <!-- the SimpleURLRegistry allows access to a URL based registry (e.g. file:/// or http://) --> |
| <registry provider="org.apache.synapse.registry.url.SimpleURLRegistry"> |
| <!-- the root property of the simple URL registry helps resolve a resource URL as root + key --> |
| <parameter name="root">file:repository/conf/sample/resources/</parameter> |
| <!-- all resources loaded from the URL registry would be cached for this number of milli seconds --> |
| <parameter name="cachableDuration">15000</parameter> |
| </registry> |
| |
| <!-- define the request processing XSLT resource as a static URL source --> |
| <localEntry key="xslt-key-req" src="file:repository/conf/sample/resources/transform/transform.xslt"/> |
| |
| <sequence name="main"> |
| <in> |
| <!-- transform the custom quote request into a standard quote requst expected by the service --> |
| <xslt key="xslt-key-req"/> |
| </in> |
| <out> |
| <!-- transform the standard response back into the custom format the client expects --> |
| <!-- the key is looked up in the remote registry and loaded as a 'dynamic' registry resource --> |
| <xslt key="transform/transform_back.xslt"/> |
| </out> |
| <send/> |
| </sequence> |
| |
| </definitions></div> |
| <subsection name="Objective"> |
| <p> |
| Demonstrating the usage of the XSLT mediator for transforming message content |
| and using local registry and remote registry for storing configuration |
| metadata. |
| </p> |
| </subsection> |
| <subsection name="Pre-requisites"> |
| <p> |
| <ul> |
| <li> |
| Deploy the SimpleStockQuoteService in the sample Axis2 server and start Axis2 |
| </li> |
| <li> |
| Start Synapse using the configuration numbered 8 (repository/conf/sample/synapse_sample_8.xml) |
| <div class="command"> |
| Unix/Linux: sh synapse.sh -sample 8<br/> |
| Windows: synapse.bat -sample 8 |
| </div> |
| </li> |
| </ul> |
| </p> |
| </subsection> |
| <subsection name="Executing the Client"> |
| <p> |
| This example uses the XSLT mediator to perform transformations, and the xslt |
| transformations are specified as registry resources. The first resource |
| 'xslt-key-req' is specified as a 'local' registry entry. Local entries do not |
| place the resource on the registry, but simply make it available to the local |
| configuration. If a local entry is defined with a key that already exists in |
| the remote registry, the local entry will get higher precedence over the remote |
| resource. |
| </p> |
| <p> |
| In this example you will notice the new 'registry' definition. Synapse comes |
| with a simple URL based registry implementation (SimpleURLRegistry). During |
| initialization of the registry, the SimpleURLRegistry expects to find a property |
| named 'root', which specifies a prefix for the registry keys used later. |
| When the SimpleURLRegistry is used, this root is prefixed to the entry keys to |
| form the complete URL of the resource being looked up. The registry caches a |
| resource once requested, and stores it internally for a specified duration. |
| Once this period expires, it will reload the meta information about the resource |
| and reloads its cached copy if necessary, the next time the resource is requested. |
| </p> |
| <p> |
| Hence the second XSLT resource key 'transform/transform_back.xslt' concatenated |
| with the 'root' of the SimpleURLRegistry 'file:repository/conf/sample/resources/' |
| forms the complete URL of the resource as |
| 'file:repository/conf/sample/resources/transform/transform_back.xslt' and caches |
| its value for a period of 15000 ms. |
| </p> |
| <p> |
| Execute the custom quote client as follows and analyze the the Synapse debug |
| log output. |
| </p> |
| <div class="command">ant stockquote -Daddurl=http://localhost:9000/services/SimpleStockQuoteService -Dtrpurl=http://localhost:8280/ -Dmode=customquote</div> |
| <p> |
| The incoming message is transformed into a standard stock quote request by the |
| XSLT mediator. The XSLT mediator uses Xalan-J to perform the transformations. |
| It is possible to configure the underlying transformation engine using properties |
| when necessary. The response from the SimpleStockQuoteService is converted back |
| into the custom format as expected by the client during the out message processing. |
| </p> |
| <p> |
| During the response processing you could see the SimpleURLRegistry fetching the |
| resource as shown by the log message below. |
| </p> |
| <div class="consoleOutput">[HttpClientWorker-1] DEBUG SimpleURLRegistry ==> Repository fetch of resource with key : transform/transform_back.xslt</div> |
| <p> |
| If you run the client again immediately (i.e within 15 seconds of the first |
| request) you will not see the resource being reloaded by the registry as the |
| cached value would be still valid. |
| </p> |
| <p> |
| However if you leave the system idle for 15 seconds or more and then retry the |
| same request, you will now notice that the registry notices the cached resource |
| has expired and will reload the meta information about the resource to check if |
| the resource has changed and will require a fresh fetch from the source URL. |
| If the meta data / version number indicates that a reload of the cached resource |
| is not necessary (i.e. unless the resource itself actually changed) the updated |
| meta information is used and the cache lease extended as appropriate. |
| </p> |
| <div class="consoleOutput">[HttpClientWorker-1] DEBUG AbstractRegistry - Cached object has expired for key : transform/transform_back.xslt |
| [HttpClientWorker-1] DEBUG SimpleURLRegistry - Perform RegistryEntry lookup for key : transform/transform_back.xslt |
| [HttpClientWorker-1] DEBUG AbstractRegistry - Expired version number is same as current version in registry |
| [HttpClientWorker-1] DEBUG AbstractRegistry - Renew cache lease for another 15s</div> |
| <p> |
| Thus the SimpleURLRegistry allows resource to be cached, and updates are detected |
| so that the configuration changes could be reloaded without restarting the |
| Synapse instance. |
| </p> |
| </subsection> |
| </section> |
| <p><a href="../samples.html">Back to Catalog</a></p> |
| </body> |
| </document> |
