Http Binding Ja

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:
```
cd [servicemix_install_dir]\examples\http-binding
```
where 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:

HTTP Binding Example Message Flow Diagram

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 and stockQuote. During initialization, several singletons are instantiated: URLEndpoint and jbi. After initialization, the components in the jbi container are activated.
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 File Binding application. The Java class files are located in the servicemix-1.0.1.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 sees it needs to instantiate a FilePoller.
The container calls the init() method of FilePoller, as well as the init() methods of its parents.
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 the servicemix.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.

PollingComponentSupport.java

  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.

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