Writing Advanced Applications - Java Wrapper

Each generated Java Wrapper class inherits methods from the EntireX Java ACI.

This section describes what can be performed with the methods inherited from the class RPCService.

Natural Logon or Changing the Library Name
Customizing the Generated Java Classes
Using RPC Compression
Using Conversational RPC
Using Natural Security
Using SSL/TLS
Support of DVIPA

Natural Logon or Changing the Library Name

The library name sent with the RPC request to the EntireX RPC or the Natural RPC Server is specified in the Software AG IDL file (see library-definition under Software AG IDL Grammar). When the RPC is executed, this library name can be overwritten.

To overwrite the library, a C Wrapper client must

Call the setLibraryName method of the generated Java Wrapper class with the new library name as a parameter.

To force the library to be considered by Natural RPC Server

Call the setNaturalLogon method of the generated Java Wrapper class with the parameter set to True.

Warning:
Natural and EntireX RPC servers behave differently regarding the library name.

See Natural Logon or Changing the Library Name.

Customizing the Generated Java Classes

You can extend the generated Java Wrapper Class of the client. By default, the generated client class is a subclass of com.softwareag.entirex.aci.RPCService. The customization component allows you to specify a class used as the superclass of the generated client class. This user-defined class (customization class) must be a subclass of com.softwareag.entirex.aci.RPCService.

When a customization class is specified, the calls to the user-exit methods onEnter, onLeave, onException and onRetry are generated.

To generate a customized Java Wrapper client

Implement your customization class. If you use a package for your customization class, specify package and class in the following step. Place the source for the customization class in the package folder, using the folder of the IDL file as package-root. The customization class needs a default constructor and one additional constructor with 4 arguments. See the example below.
Specify the name of your customization class in the EntireX Workbench, under Tools, Options, Java. This name is stored in the entirex.properties file (which is in your home directory) using the key entirex.wrapper.custom.class.
Generate the wrapper client classes

To use the customized Java Wrapper client

Add (public) arbitrary methods and fields to your customization class. These methods and fields are inherited by the generated client class. Add your own processing instructions to these methods.

To perform all Broker-related processing in the generated Java Wrapper client

Overwrite the constructors of RPCService. You can instantiate wrapper classes without specifying a Broker object and server address as a parameter. Use the method setbroker() to set or change the reference to the Broker object, and the method setServerAddress() to set or change the server address.
Use the four user exit methods onEnter, onLeave, onException and onRetry. These methods have default implementations in RPCService and can be overwritten in your customization class. These exits are called at the beginning and the end of each generated method of the Java Wrapper class and when a broker exception is thrown. See RPCService.

Example of a Customization Class

package ExamplePackage;

import com.softwareag.entirex.aci.Broker;
import com.softwareag.entirex.aci.BrokerException;
import com.softwareag.entirex.aci.RPCService;

public class ExampleCustomization extends RPCService {
   public ExampleCustomization ()
   {
      super();
   }
   public ExampleCustomization (Broker broker, String serverAddr, String
libName, boolean compress)
   {
      super(broker, serverAddr, libName, compress);
   }
   protected void onEnter(String progname) throws BrokerException {
      // insert your implementation here.
   }

   protected void onLeave(String progname, int sendLen, int receiveLen) throws
BrokerException {
      // insert your implementation here.
   }

   protected void onException(String progname, BrokerException exception) throws
BrokerException {
      // insert your implementation here.
   }

   protected boolean onRetry(String progname, BrokerException exception) throws
BrokerException {
      // insert your implementation here.
      return false;
   }
}

Using RPC Compression

EntireX and Natural RPC support a feature called RPC compression to reduce network traffic. The default for compression is on. See RPC Compression.

To switch compression on and off

Use the setCompression method of the class RPCService.

To check the current compression setting

Use the getCompression method of the class RPCService.

Using Conversational RPC

It is assumed that you are familiar with the concepts of conversational and non-conversational RPC. See Conversational RPC.

To enable conversational RPC

Create a Conversation object and set this with setConversation on the wrapper object.
Different wrapper objects can participate in the same conversation if they use the same instance of a conversation object.

To abort a conversational RPC communication

Abort an RPC conversation by calling the closeConversation method

To close and commit a conversational RPC communication

Commit the RPC conversation by calling the closeConversationCommit method.

Warning:
Natural RPC Servers and EntireX RPC Servers behave differently when ending an RPC conversation.

See Conversational RPC.

Using Natural Security

A Natural RPC Server may run under Natural Security to protect RPC requests. See Natural Security under Common Features of Wrappers and RPC-based Components.

To authenticate a Java Wrapper client against Natural Security

Specify a user ID and password in the logon method of class Broker.

If different user IDs and/or passwords are used for EntireX Security and Natural Security, use the methods setRPCUserId or setRPCPassword to set the user IDs and/or passwords for Natural Security.

To force a Java Wrapper client to log on to a specific Natural library

Call the setLibraryName method of the generated wrapper objects with the new library name as a parameter.
Call the setNaturalLogon method of the generated wrapper objects with the parameter set to true.

Example:

Assume that library is a wrapper object that is generated from an IDL library. This object extends com.softwareag.entirex.aci.RPCService. For this object, call the methods as shown:

library.setRPCUserId("testuser");
library.setRPCPassword("password");
library.setLibraryName("NATLIB");  // this is necessary only if the Natural Library
                                   // name is different from the library name in the IDL.
library.setNaturalLogon(true);

The order of the four methods is arbitrary.

Using SSL/TLS

RPC client applications can use Secure Sockets Layer/Transport Layer Security (SSL/TLS) as the transport medium. The term "SSL" in this section refers to both SSL and TLS. RPC-based clients are always SSL clients. The SSL server can be either the EntireX Broker, Broker SSL Agent, or Direct RPC in webMethods Integration Server (IS inbound). For an introduction see SSL/TLS and Certificates in the Security documentation.

To use SSL

To operate with SSL, certificates need to be provided and maintained. Depending on the platform, Software AG provides default certificates, but we strongly recommend that you create your own. See Default Certificates Delivered with EntireX under SSL/TLS and Certificates with EntireX in the Security documentation.
Specify Broker ID and SSL parameters.

SSL transport will be chosen if the Broker ID starts with the string ssl://. Example of a typical URL-style Broker ID:
```
Broker broker = new Broker("ssl://yourbroker:10000?trust_store=castore","userID");
```
If no port number is specified, port 1958 is used as default.

If the SSL client checks the validity of the SSL server only, this is known as one-way SSL. The mandatory trust_store parameter specifies the file name of a keystore that must contain the list of trusted certificate authorities for the certificate of the SSL server. By default a check is made that the certificate of the SSL server is issued for the hostname specified in the Broker ID. The common name of the subject entry in the server's certificate is checked against the hostname. If they do not match, the connection will be refused. You can disable this check with SSL parameter verify_server=no.

If the SSL server additionally checks the identity of the SSL client, this is known as two-way SSL. In this case the SSL server requests a client certificate (the parameter verify_client=yes is defined in the configuration of the SSL server). Two additional SSL parameters must be specified on the SSL client side: key_store and key_passwd. This keystore must contain the private key of the SSL client. The password that protects the private key is specified with key_passwd.

The ampersand (&) character cannot appear in the password.

SSL parameters are separated by ampersand (&). See also SSL/TLS Parameters for EntireX Clients and Servers.

Example of one-way SSL:
```
Broker broker = new Broker("ssl://yourbroker:10000?trust_store=castore?verify_server=no","userID");
```
Example of two-way SSL:
```
Broker broker = new Broker("ssl://yourbroker:10000?trust_store=castore&key_store=keystore&key_passwd=pwd","userID");
```
Make sure the SSL server to which the RPC component connects is prepared for SSL connections as well. The SSL server can be EntireX Broker, Broker SSL Agent, or Direct RPC in webMethods Integration Server (IS inbound). See:
- Running Broker with SSL/TLS Transport under z/OS | UNIX | Windows | z/VSE
- Settting up and Administering the EntireX Broker SSL Agent under UNIX | Windows
- Support for SSL/TLS in the EntireX Adapter documentation (for Direct RPC)

Support of DVIPA

A TCP/IP connection established between stub and broker is not exclusively assigned to a particular thread. With multi-threaded applications, two or more threads may use the same connection. On the other hand, if a connection is busy, another new one is created to exchange data.

In order to access the same z/OS broker instance in a DVIPA-controlled environment, an affinity between application thread and TCP/IP connection is needed to always use the same connection within an application thread. Therefore, an environment variable is evaluated to control the handling of TCP/IP connections.

If broker ID contains the parameter "poolsize=0" (e.g. ETB001?poolsize=0), an affinity between threads and TCP/IP connections is established. All requests to one particular broker will use the same TCP/IP connection.

See also Support of Clustering in a High Availability Scenario under z/OS | UNIX | Windows.