Configure JAX-RS App with an XA-Compliant Resource Manager

6.9.3.1 Configure JAX-RS App with an XA-Compliant Resource Manager

Use the information provided in this section to configure your JAX-RS participant applications when you use an XA-compliant resource manager.

Configure property values for the MicroTx client library.
The following example provides sample values for the properties. Provide the values based on your environment.
```
oracle.tmm.TcsConnPoolSize = 15
oracle.tmm.CallbackUrl = https://bookTicket-app:8081
oracle.tmm.PropagateTraceHeaders = true
oracle.tmm.TransactionTimeout = 60000
oracle.tmm.xa.XaSupport = true
```
Ensure that oracle.tmm.xa.XaSupport is set to true.

For details about each property and other optional properties, see Configure Library Properties.
Include the MicroTx Java library file as a maven dependency in the application's pom.xml file. The following sample code is for the 24.2 release. Provide the correct version, based on the release version that you want to use.
- In Jakarta EE8 environments, such as Helidon 2.x, use the TmmLib file.
```
<dependency>
     <groupId>com.oracle.tmm.jta</groupId>
     <artifactId>TmmLib</artifactId>
     <version>24.2</version>
</dependency>
```
- In Jakarta EE9 environments, such as Helidon 3.x applications, use the TmmLib-jakarta file.
```
<dependency>
     <groupId>com.oracle.tmm.jta</groupId>
     <artifactId>TmmLib-jakarta</artifactId>
     <version>24.2</version>
</dependency>
```
Initialize an XADatasource object.
The MicroTx client library needs to access an XADatasource object. It uses this object to create XAConnection and XAResource objects to connect with a resource manager or database server. The following code describes how you can define the XADatasource object at the beginning of the application code when you create the connection object.
```
class oracle.tmm.jta.TrmConfig
static void initXaDataSource(XADataSource xaDs)
```
For more information about XADataSource, see https://docs.oracle.com/javase/8/docs/api/javax/sql/XADataSource.html.
In the transaction participant function or block, specify the XADatasource object which is used by the MicroTx client library. Provide the credentials and other details to connect to the resource manager.
```
//Example for a participant using an Oracle Database:
OracleXADataSource dataSource = new oracle.jdbc.xa.client.OracleXADataSource();
dataSource.setURL(url); //database connection string
dataSource.setUser(user); //username to access database
dataSource.setPassword(password); //password to access database
TrmConfig.initXaDataSource((XADataSource)dataSource);
```
It is the responsibility of the application developer to ensure that an XA-compliant JDBC driver and required parameters are set up while allocating XADataSource.

The MicroTx client library uses the XADatasource object to create database connections.
In the transaction participant function or block, add the following line of code only once after you have initialized the XADatasource object.
```
oracle.tmm.jta.TrmConfig.initXaDataSource((XADataSource)xaDs);
```
XADatasource is an interface defined in JTA whose implementation is provided by the JDBC driver.

The MicroTx client library uses this object to connect to database to start XA transactions and perform various operations such as prepare, commit, and rollback. The MicroTx library also provides a SQL connection object to the application code to execute DML using dependency injection.
Insert the following line in the code of the participant service so that the application uses the connection passed by the MicroTx client library. The following code in the participant application injects the connection object that is created by the MicroTx client library.
```
@Inject
@TrmSQLConnection 
private Connection connection;
```
Insert the following lines in the code of the participant service so that the service uses the injected connection object whenever the participant service performs a DML operation.
```
Statement stmt1 = connection.createStatement();
stmt1.execute(query);
stmt1.close();
```
Where, connection is the name of the Connection object that you have injected in the previous step.

Insert these lines of code for every DML operation that your participant service performs. Create a new statement object, such as stmt1 or stmt2 for every DML operation, but use the same connection object that is created by the MicroTx client library.

Only for Spring Boot applications that use the JAX-RS API, perform the following tasks after registering the resource endpoint that participates in the XA transaction.

Register the filters and XAResourceCallbacks for prepare, commit, rollback as shown in the following sample code snippet.

@Component
public class JerseyConfig extends ResourceConfig
{
    public JerseyConfig()
    {
        // Register the MicroTx XA resource callback which
        // coordinates with the transaction coordinator
        register(XAResourceCallbacks.class);
        // Register the filters for the MicroTx libraries that 
        // intercept the JAX_RS calls and manage the XA transactions
        register(TrmTransactionResponseFilter.class);
        register(TrmTransactionRequestFilter.class);
        
        // Bind the connection
        ...
    }
}

If you are using a single resource manager with your Spring Boot application, bind the TrmXAConnectionFactory object to an XAConnection. Later, you will use the TrmXAConnectionFactory object, a MicroTx connection factory object, so that MicroTx handles the connection.

@Component
public class JerseyConfig extends ResourceConfig
{
    public JerseyConfig()
    {
        // Register the filters as shown in the previous step
        ....

        register(new AbstractBinder() {
            @Override
            protected void configure() {
            //Bind the TrmXAConnectionFactory object to an XAConnection object
            bindFactory(TrmXAConnectionFactory.class).to(XAConnection.class);
            }
        });
    }
}

Save the changes.

If there are multiple JAX-RS transaction participant services complete these steps for all the participant services.

Parent topic: Configure JAX-RS App as Transaction Participant