A JSON HelloWorld BPEL process

Introduction

In several previous posts I've discussed various issues encountered when trying to build a HelloWorld JSON BPEL process. Such as;

Differences between JSON and XML and an example of a simple conversion
- http://javaoraclesoa.blogspot.nl/2012/07/webinterface-restjson-vs-middleware.html

Receiving JSON requests in BPEL by using the SocketAdapter
- http://javaoraclesoa.blogspot.nl/2012/12/receiving-json-requests-in-oracle-bpel.html

A reusable solution for transforming from JSON to XML and back again in order to avoid a mapping layer.
- http://javaoraclesoa.blogspot.nl/2012/12/a-reusable-solution-for-conversion.html

In this post I'm expanding on the above posts and putting the things I've created together to provide a working example of how BPEL and Json can interoperate with each other in a reusable way. In this example I'll show how JSON can be received in BPEL, can be transformed to XML and be edited in BPEL (using XSLT). The result is then transformed back to JSON and returned to the requester.

Implementation

Receiving Json

A JSON message is received by using the SocketAdapter. As mentioned in a previous post, the request and response can be parsed by using XSLT functions. This however is difficult and not safe. For example, the inbound request contains HTTP headers. These headers tell things about the HTTP body. I would have to use XPath functions in order to create an HTTP interpreter. This did not seem the way to go (as concluded before) so I've used a different approach. I've a custom Java class which used Apache HttpComponents (http://hc.apache.org/) to provide the HTTP implementation and parsing of the incoming request. The code can be downloaded at the end of this post.

Editing JSON in BPEL

I've used my previously created Webservice to convert Json to XML and back to Json as described on; http://javaoraclesoa.blogspot.nl/2012/12/a-reusable-solution-for-conversion.html. This way I could do XSLT transformations on XML describing JSON messages and later go back to JSON again when sending the reply.

The result

First I've tested my service by using SOAP UI. The result can be seen below;

Next I looked up my BPEL process in the Fusion Middleware Console

 

This way you can exactly see what has happened to the JSON code. First it is received. Then it is translated to XML. Next XSLT is used to transform the resulting XML. This resulting XML is transformed back to JSON and the result is replied to the caller.

I've also tried opening the service in a webbrowser with the expected result (a normal GET HTTP request doesn't contain a body);

Performance

Sometimes stories are told about poor performance of BPEL and the large overhead incurred by using SOAP and XML. Since I was curious about this (claims should of course be tested!) I've done a small measure on my HelloWorldJSONBPEL service;

As can be seen in the screenshot above, 68ms is the average response time under high load. This was however not an optimized process on development audit logging running on a server in a virtual machine on my desktop. This performance does not surprise or worry me, I can however imagine that a plain Java servlet receiving/replying JSON is faster. I've not created such a servlet to test this. In plain Java however you won't be able to use some of the advanced monitoring tools of the SOA Suite.

Conclusion

Reusable interoperability between JSON and XML is possible. It requires however some work and figuring out. Also if you want to use different endpoints on the same port, some routing is required based on the status line in the HttpRequest. Security is also an issue. If you want to secure the SocketAdapter port you can implement HTTP classes which support authentication mechanisms or you can use for example a service bus to provide this functionality. It requires some tweaking though.

Something I'm not happy about is the sending of the HTTP response. I'm still manually providing HTTP header lines. This should not be needed when working with the Apache HttpComponents.

An expectation is that the 12c release of the SOA Suite which will be released somewhere half 2013 will contain better JSON support. Also see http://technology.amis.nl/wp-content/uploads/2012/11/AMIS-Whitepaper-OOW-2012.pdf. This would render custom implementations obsolete if the implementation provided in that release is sufficient.

You can download the complete sample project here; https://dl.dropbox.com/u/6693935/blog/JsonExample.zip

Receiving JSON requests in Oracle BPEL by using the SocketAdapter

Some frameworks prefer the use of JSON, such as webinterface frameworks, GIS frameworks or mobile app frameworks. In order to integrate and provide for example service orchestration, Oracle SOA Suite can be used. Oracle SOA Suite however does not have a JSONAdapter in the current release.

Using the HTTPAdapter is not an option to provide JSON support. The Oracle HTTPAdapter does not support receiving and sending JSON (only XML). It can however be used to send a HTTP GET request with parameters which is how REST services are often called. See for example; http://shrikworld.blogspot.nl/2011/04/http-adapter-in-soa-11g.html

The SocketAdapter however does not have the XML limitations of the HTTPAdapter. In this post I describe how the SocketAdapter can be used to receive a JSON message from an HTTP Post request.

Implementation

SocketAdapter

To use the  SocketAdapter for this usecase requires some parsing of the HTTP communication which is usually abstracted. It is possible to use XSLT or a custom Java class to parse the request received from the adapter and transform it to XML (http://docs.oracle.com/cd/E21764_01/integration.1111/e10231/adptr_sock.htm#BABHECAG). I decided to try the XSLT option.

I downloaded an example from; http://java.net/projects/oraclesoasuite11g/pages/SocketAdapters

In this example I needed to change the following to get it to work;
- update adf-config.xml with the correct path of the jdeveloper/integration folder
- make sure bpm-infra.jar is in the classpath of the server

Based on the configuration of the SocketAdapter connection factory I tried connecting to port 12110 with telnet.

In the logfile I saw the following;

- Socket Adapter ClientProcessor:run() Error occured in processing client request
- Socket Stylesheet Parsing Error.
Error while trying to parse the stylesheet.
Please ensure that that the stylesheet exists and is configured properly. Please cross check the extension functions. Contact Oracle support if error is not fixable. 

This was as expected since I didn't provide the correct test message.

When I opened in my browser; http://localhost:12110 it did work however. I noticed the input was;

0.9,*/*

I wondered where this came from. I created a custom Java socket listener based on http://docs.oracle.com/javase/tutorial/networking/sockets/readingWriting.html and http://zerioh.tripod.com/ressources/sockets.html and did the request on the listener. The result was;

client>GET / HTTP/1.1
client>Host: localhost:2004
client>User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20100101 Firefox/16.0
client>Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
client>Accept-Language: en-US,en;q=0.5
client>Accept-Encoding: gzip, deflate
client>Connection: keep-alive

The request.xsl from the example was as followed;

<?xml version="1.0" encoding="windows-1252" ?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:ora="http://www.oracle.com/XSL/Transform/java/"
                xmlns:socket="http://www.oracle.com/XSL/Transform/java/oracle.tip.adapter.socket.ProtocolTranslator"
                xmlns="http://xmlns.oracle.com/HelloWorld">
 <!-- Root template -->
 <xsl:template match="//input">
  <!-- Input coming from the browser would look like
  GET /input=sagar; HTTP/1.1.
  dummy variable to read the input= text -->
  <xsl:variable name="variable1"
                select="socket:socketRead('terminated', 'terminatedBy==')"/>
               
  <!-- Read the input string terminated by ;and build the input xml -->
  <HelloWorldProcessRequest>
   <input>
    <xsl:value-of select="socket:socketRead('terminated', 'terminatedBy=;')"/>
   </input>
  </HelloWorldProcessRequest>
 </xsl:template>
</xsl:stylesheet>


The SocketAdapter took the part from the first = sign to the first ; after that. This was confirmed by looking at the log set to trace level.

When trying again with telnet with the input;
input=Maarten;

It worked and I got an instance of my process. I was however not yet able to receive JSON from a HTTP POST request. First I needed an example request;

POST /request HTTP/1.1
Accept: application/jsonrequest
Content-Length: 123
Content-Type: application/jsonrequest
Host: localhost

{"user":"test","var":7,"t":"something","stuff":123}

I needed to extract everything after the first empty line (I'm not sure yet if this is always the case in HTTP messages!) to the end of the message. This way if the JSON message was multiline, it would also work. To do that I needed to understand the XPath function socket:socketRead used in the XSLT transformation used by the SocketAdapter when receiving the message

I found the following (http://docs.oracle.com/cd/E21764_01/integration.1111/e10231/adptr_sock.htm#BABHECAG);

"By using StyleReader, which is exposed by the NXSD framework, to read and write from the socket stream using the following methods: socketRead(nxsdStyle:String, nxsdStyleAttributes:String):String"

I remembered from the Native Format Builder (which also uses the NXSD framework) some codes I could use in the terminatedBy clause. The resulting XSLT for my usecase was;

<?xml version="1.0" encoding="windows-1252" ?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:ora="http://www.oracle.com/XSL/Transform/java/"
                xmlns:socket="http://www.oracle.com/XSL/Transform/java/oracle.tip.adapter.socket.ProtocolTranslator"
                xmlns="http://xmlns.oracle.com/HelloWorld">
 <!-- Root template -->
 <xsl:template match="//input">
  <!-- Input coming from the browser would look like
  GET /input=sagar; HTTP/1.1.
  dummy variable to read the input= text -->
  <xsl:variable name="variable1"
                select="socket:socketRead('terminated', 'terminatedBy=${eol}${eol}')"/>
              
  <!-- Read the input string terminated by ;and build the input xml -->
  <HelloWorldProcessRequest>
   <input>
    <xsl:value-of select="socket:socketRead('terminated', 'terminatedBy=${eof}')"/>
   </input>
  </HelloWorldProcessRequest>
 </xsl:template>
</xsl:stylesheet>

With this XSLT to parse the request I could obtain the JSON String from a HTTP POST request. This is the first step in creating a BPEL JSON HelloWorld service.

JsonPath

The parsing or querying of a JSON String can be done in several ways such as using the JsonPath (http://code.google.com/p/json-path/). Below is code for an example webservice which can be used.

package ms.testapp.soa.utils;

import com.jayway.jsonpath.JsonPath;

import javax.jws.WebParam;
import javax.jws.WebResult;
import javax.jws.WebService;

@WebService
public class JsonPathUtils {
   
    @WebResult(name = "result")
    public String ExecuteJsonPath(@WebParam(name = "jsonstring") String jsonstring, @WebParam(name = "jsonpath")String jsonpath) {
        String result = JsonPath.read(jsonstring, jsonpath).toString();
        return result;
    }
   
    public JsonPathUtils() {
        super();
    }
/*   
    public static void main(String[] args) {
        JsonPathUtils myPath = new JsonPathUtils();
        System.out.println(myPath.ExecuteJsonPath("{ \"store\": {\n" +
        "    \"book\": [ \n" +
        "      { \"category\": \"reference\",\n" +
        "        \"author\": \"Nigel Rees\",\n" +
        "        \"title\": \"Sayings of the Century\",\n" +
        "        \"price\": 8.95\n" +
        "      },\n" +
        "      { \"category\": \"fiction\",\n" +
        "        \"author\": \"Evelyn Waugh\",\n" +
        "        \"title\": \"Sword of Honour\",\n" +
        "        \"price\": 12.99,\n" +
        "        \"isbn\": \"0-553-21311-3\"\n" +
        "      }\n" +
        "    ],\n" +
        "    \"bicycle\": {\n" +
        "      \"color\": \"red\",\n" +
        "      \"price\": 19.95\n" +
        "    }\n" +
        "  }\n" +
        "}", "$.store.book[1].author"));
    }
*/
}

Conclusion

I haven't finished the HelloWorld BPEL JSON service implementation yet. What I've found however is that it requires some work to get relatively simple functionality.

Not only does it require some work, but to make the code reusuable is also a challenge. You will need routing mechanisms which sounds a lot like where the OSB is really good at.
JSON is often used when performance is important. JSON messages can be smaller then XML messages and a strict message or interface definition (such as for XML XSD/WSDL) is not a requirement. Also the (Java) frameworks required to work with JSON are often relatively easy to implement making quick development possible. When using the above solution, several components are used which cause additional overhead (such as the SocketAdapter and XSLT transformations). This is expensive when considering there can be a relatively light and easy implementation by using the OSB or custom Java code per integration.