Details

    • Type: Improvement Improvement
    • Status: Resolved
    • Priority: Major Major
    • Resolution: Fixed
    • Affects Version/s: 3.2
    • Fix Version/s: 3.2
    • Labels:
      None

      Description

      The thesis is to eliminate the Connector-specfic JavaBean which is currently the heart of the MDB/Connector model. The @ActivationConfigProperty is just a reflection of that Connector JavaBean.

      There are several disadvantages to the JavaBean approach and current Connector style:

      • Metadata is loosely typed in the bean code
      • Only class-level metadata is allowed, not method-level
      • Requiring an interface can limit API expressiveness

      For those that aren't intimately familiar with the Connector and MDB relationship, see the blog post EJB.next Connector and Bean API for explanation and this github project, MDB Improvements: Telnet Connector for an actual functioning connector.

      The core proposal

      The short version of the proposal is as follows:

      • Allow the ResourceAdapter to obtain the bean class through the ActivationSpec
      • Allow the ResourceAdapter to obtain a no-interface view of the bean

      This can be done with text and no new API classes or signatures are required. The contract would be simple.

      • The Connector Provider can request the MDB implementation class (ejb class) via the ActivationSpec
      • If the ActivationSpec has an 'ejbClass' property the MDB Container would be required to:
        • set a reference to the ejb class of the MDB when creating the ActivationSpec instance
        • return a no-interface view of the MDB from the MessageEndpointFactory.createEndpoint method

      Of course the "no-interface" view would still implement MessageEndpoint and the message listener interface.

      Optional no-interface MDB contract

      Instead of requiring Connectors to supply a regular interface such as 'public interface Foo' as the <messagelistener-type>, allow the Connector to supply a an annotation such as public @interface Foo as the message listener interface. The MDB use that on the bean class.

      Modernized MDB Examples

      Some of the possibilities this would open up:

      @MessageDriven
      @EmailAccountInfo(address = "dblevins@apache.org")
      public class EmailBean {
      
          @PostConstruct
          public void init() {
          }
      
          @Deliver @Header("Subject: {subject}")
          public void receiveEmail(@HeaderParam("subject") String subject, @Body String body) {
              // do your thing!
          }
      }
      

      EmailAccountInfo, Header, Deliver, HeaderParam, and Body are all annotations supplied by the Connector demonstrating the "JAX-RS" like APIs that could be written and standardly used via custom connector. The APIs themselves could of course become standard, but that would not be necessary – the connector itself could be run in any compliant server.

      Another example of an MDB that accepts commands issued in a telnet console:

      package org.developer.application;
      
      import com.superconnectors.telnet.api.Command;
      import com.superconnectors.telnet.api.Option;
      import com.superconnectors.telnet.api.TelnetListener;
      
      import javax.ejb.ActivationConfigProperty;
      import javax.ejb.MessageDriven;
      import java.text.SimpleDateFormat;
      import java.util.Date;
      import java.util.Map;
      import java.util.Properties;
      import java.util.regex.Pattern;
      
      @MessageDriven
      @TelnetListener
      public class MyMdb {
      
          private final Properties properties = new Properties();
      
          @Command("get")
          public String doGet(@Option("key") String key) {
              return properties.getProperty(key);
          }
      
          @Command("set")
          public String doSet(@Option("key") String key, @Option("value") String value) {
      
              final Object old = properties.setProperty(key, value);
              final StringBuilder sb = new StringBuilder();
              sb.append("set ").append(key).append(" to ").append(value);
              sb.append("\n");
              if (old != null) {
                  sb.append("old value: ").append(old);
                  sb.append("\n");
              }
              return sb.toString();
          }
      
          @Command("list")
          public String doList(@Option("pattern") Pattern pattern) {
      
              if (pattern == null) pattern = Pattern.compile(".*");
              final StringBuilder sb = new StringBuilder();
              for (Map.Entry<Object, Object> entry : properties.entrySet()) {
                  final String key = entry.getKey().toString();
                  if (pattern.matcher(key).matches()) {
                      sb.append(key).append(" = ").append(entry.getValue()).append("\n");
                  }
              }
              return sb.toString();
          }
      }
      

        Issue Links

          Activity

          Hide
          marina vatkina added a comment -

          We are discussing the options...

          Show
          marina vatkina added a comment - We are discussing the options...
          Show
          marina vatkina added a comment - See http://java.net/projects/javaee-spec/lists/jsr342-experts/archive/2013-03/message/2
          Hide
          rherschke added a comment -

          For me the inbound ra spec and mdb binding should be reworked soon. Davids proposals as mentioned in the beginning of this issue is a huge step forward to get JCA on the mainstream again.

          I understand, that these changes will have a large impact and thatswhy I can go with Bill's compromise for now. The getEndpointClass() is at least a good idea to let the RA's developer parse the metadata by itself and do the right thing.

          Also an empty Message Listener Interface to tag those classes is fine for EE 7.

          Nonetheless, I definetely prefere to see the whole improvement package in EE 8 besides some changes for outbound connectors too (e.g. get rid of those "GenericManagedConnection/Factory" classes by having some declarative "ManagedConnection" annotations for the real connection impls).

          So +1 for Bill's compromise, but also +100 for the next steps in David's proposals.

          (as well as +999 for a complete JCA rework allthough this is the wrong place to vote for that)

          Regards,
          Robert

          Show
          rherschke added a comment - For me the inbound ra spec and mdb binding should be reworked soon. Davids proposals as mentioned in the beginning of this issue is a huge step forward to get JCA on the mainstream again. I understand, that these changes will have a large impact and thatswhy I can go with Bill's compromise for now. The getEndpointClass() is at least a good idea to let the RA's developer parse the metadata by itself and do the right thing. Also an empty Message Listener Interface to tag those classes is fine for EE 7. Nonetheless, I definetely prefere to see the whole improvement package in EE 8 besides some changes for outbound connectors too (e.g. get rid of those "GenericManagedConnection/Factory" classes by having some declarative "ManagedConnection" annotations for the real connection impls). So +1 for Bill's compromise, but also +100 for the next steps in David's proposals. (as well as +999 for a complete JCA rework allthough this is the wrong place to vote for that) Regards, Robert
          Hide
          marina vatkina added a comment -

          And the simplified version with a marker message-listener interface is in!

          David, please create another issue for using annotations directly and mark it for the future version.

          Show
          marina vatkina added a comment - And the simplified version with a marker message-listener interface is in! David, please create another issue for using annotations directly and mark it for the future version.
          Hide
          Nigel Deakin added a comment -

          I have logged EJB_SPEC-126 which proposes removal of the requirement to implement a no-method marker interface.

          Show
          Nigel Deakin added a comment - I have logged EJB_SPEC-126 which proposes removal of the requirement to implement a no-method marker interface.

            People

            • Assignee:
              marina vatkina
              Reporter:
              dblevins
            • Votes:
              25 Vote for this issue
              Watchers:
              16 Start watching this issue

              Dates

              • Created:
                Updated:
                Resolved: