Overview of the ServiceMix 2.x HTTP Binding Example
The following procedure describes how to run the HTTP Binding example and provides details regarding what it does. For information on the business use case, please refer to: Use Case for HTTP Binding.
The HTTP Binding example illustrates:
- use of declarative programming
- how to perform HTTP binding in ServiceMix
The source code for the HTTP Binding example is located in the ServiceMix installation directory under the examples\http-binding
directory in the servicemix.xml
file. It is recommended that you refer to the source code while reading this document.
This example shows how to use the HTTP bindings to handle a simple HTTP post. One component acts as the HTTP server thahttp://docs.codehaus.org/display/SM/Http+Binding+Ja
Viewt listens on http://localhost:8912 while another invokes a remote service implemented as a URLEndpoint. A simple HTTP client is provided so that a simple post can be set to the server.
Running the HTTP Binding Example
- From a command shell, go to the HTTP Binding example directory:
where
cd [servicemix_install_dir]\examples\http-binding
servicemix_install_dir
is the directory in which ServiceMix was installed. - Then type:
[servicemix_install_dir]\bin\servicemix servicemix.xml
- To start sending and receiving of messages from the HTTP server, send an initial message. To do this, compile and run a simple HTTP client. The client is built and run from source code using Ant. Execute Ant from the HTTP Binding directory:
servicemix_install_dir\examples\http-binding
. To run the HTTP client type:
ant
Ant will compile and run the simple HTTP client, HttpClient, which performs a simple post on the HTTP Server into the ServiceMix container before returning the results to the console.
Stopping the HTTP Binding Example
To terminate the HTTP Binding example, type "CTRL-C" in the command shell in which it is running and answer "y" to the "Terminate batch job (y/n)?" question.
How it Works
The diagram below illustrates the flow of messages through the HTTP Binding components:
Messages flow through the components as follows:
- HttpClient, a java standalone program connects to http://localhost:8912
through URLConnection class. It then sends the file "request.xml" to this port.
- httpReceiver, an http server, being a listenser on http://localhost:8912
receives the message.
- It then sends the message to stockQuote as specified in its destinationService property, via NMR.
- stockQuote sends in into another service, soapEndpoint for processing.
- soapEndpoint sends the response to stockQuote.
- stockQuote send the response to httpReceiver via NMR.
- httpReceiver sends the response to http://localhost:8912
.
- HttpClient reads the response.
- The response is printed on the console.
Typical output looks like the following:
Output of servicemix servicemix.xml
Loading ServiceMix from file: C:\exist\servicemix\servicemix-2.0.2\examples\http -binding\servicemix.xml 17:34:34.768 EVENT Starting Jetty/4.2.20RC0 17:34:34.848 EVENT Started ServletHttpContext[/] 17:34:34.858 EVENT Started SocketListener on 127.0.0.1:8912 17:34:34.858 EVENT Started org.mortbay.jetty.Server@1f06dc3
Output of HttpClient.java
Buildfile: build.xml init: compile: run: [echo] Running example client [java] <?xml version="1.0" encoding="UTF-8"?><soap:Envelope xmlns:soap="htt p://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSch ema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenc="http:/ /schemas.xmlsoap.org/soap/encoding/" soap:encodingStyle="http://schemas.xmlsoap. org/soap/encoding/"><soap:Body><n:getQuoteResponse xmlns:n="urn:xmethods-delayed -quotes"><Result xsi:type="xsd:float">88.8</Result></n:getQuoteResponse></soap:B ody></soap:Envelope>asdf BUILD SUCCESSFUL Total time: 6 seconds
Details
The following table provides more details about the function of each component and bean in the servicemix.xml file.
Component or Bean ID |
Description |
---|---|
jbi |
jbi is the "id" of the JBI container and provides the basic infrastructure services for the following components: |
httpReceiver |
This component is an http server that is set to listen at http://localhost/8912![]() . It forwards the message it receives from this url to stockQuote as specified in its property destinationService. |
stockQuote |
This is a SaajBinding component that invokes an endpoint service called soapEndpoint. It is implemented by the SaajBinding class which converts an inbound JBI message into a SAAJ (Soap With Attachments for Java) request-response and outputs the response back into httpReceiver. This provides a message centric way of invoking SOAP services inside providers such as Apache Axis |
soapEndpoint |
A URLEndpoint object contains a URL, which is used to make connections to the remote party. A standalone client can pass a URLEndpoint object to the SOAPConnection method call to send a message. |
Useful Code Hints
This section describes the start-up sequence and how the ServiceMix container interacts with the HTTP Binding application. The Java class files are located in the servicemix-2.0.2.jar file in the ServiceMix installation directory. To look at the Java source code, unjar and decompile the .class files or download the source code. Please note: the downloadable source code is slightly different than the compiled binary code.
Viewing the Java source code is recommended for understanding the information in this section.
filePoller Details
- The ServiceMix container reads the
servicemix.xml
file and instantiates the components specified through SpringJBIContainer. - SpringJBIContainer registers the components and the activationSpecs in its afterPropertiesSet method. In this case, httpReceiver and stockQuote are registered as activationSpecs.
- SpringJBIContainer uses ActivationSpec class as the container for the component specific properties such as routing information.
- The container determines that FilePoller is an MBean and, therefore, calls the start() method of FilePoller, which it inherits from its parent PollingComponentSupport.
- The start() method will: (See: PollingComponentSupport.java code fragment below)
A. Create a timerTask.
B. Schedule the timerTask at a fixed rate. The start() method uses the "timer" (created in the init method) to schedule the timerTask at a fixed rate: timer.scheduleAtFixedRate(timerTask, firstTime, period). Recall "period" is a property of FilePoller. It was assigned the value of 1000ms by dependency injection from theservicemix.xml
file.
C. timer will call the run() method of the timerTask periodically. timerTask's run method() is defined inline. This run() method will get the workManager object (see below for details).
D. The workManager will call "scheduleWork(PollingComponentSupport.this)". Note: it passes in PollingComponent support, which by virtue of its inheritance hierarchy, is of type "Work", which is a "Runnable" object.
E. "workManager.scheduleWork(Work)" will get a Thread, passing in a Runnable object, i.e. PollingComponentSupport, and call its run() method.
F. PollingComponent's run() method calls poll(), which is implemented in FilePoller.
G. From this point on the call sequence can be followed in FilePoller...
H. The start() method of PollingComponentSupport, will eventually call super.start(), which propagates up to call the start() method of BaseLifeCycle, which sets the component state to "RUNNING."
Eventually, one of the threads that is polling (see step G) for a file in the inbox
directory will see a one. It will use workManager's thread pool to get a thread for processing the file. Processing the file consists of streaming it from inbox
, creating a normalized message, and sending the message to the NMR.
timerTask = new TimerTask() { public void run() { try { getWorkManager().scheduleWork(PollingComponentSupport.this); } catch (Throwable e) { log.error("Failed to schedule work: " + e, e); } } }; if (firstTime != null) { timer.scheduleAtFixedRate(timerTask, firstTime, period); } else { timer.scheduleAtFixedRate(timerTask, delay, period); } } super.start();
workManager Details
workManager is a property of the FilePoller object. This property is defined by a local reference, the "ref" attribute in the servicemix.xml
file. The local reference is a bean which instantiates org.activemq.work.SpringWorkManager.
The SpringWorkManager is a Spring bean. By default when a Spring bean starts, the properties are set, and then the afterPropertiesSet() method is called by the container.
The workManager is used to allocate threads. The FilePoller asks for threads from the workManager for two operations:
- The timerTask uses threads from the thread pool to periodically check the
inbox
directory for files. - The workManager will also allocate a thread to process a file (read, normalize and send to NMR). The workManager calls a scheduleWork() method which is non-blocking. Therefore, if multiple files need to be processed, FilePoller can continue making requests to the workManager to schedule work.
Related Documentation
For more information on the following topics please see: