Configure Spring REST App with Multiple XA-Compliant Resource Managers

6.10.3.2 Configure Spring REST App with Multiple XA-Compliant Resource Managers

Use the information provided in this section to configure your Spring REST participant applications when you use multiple XA-compliant resource managers.

Your application can connect to multiple XA-compliant resource managers. Additionally, your application can connect to a single non-XA resource.

Include only one of the following MicroTx library files as a maven dependency in the Spring Boot 3.x 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. Spring Boot 3.x applications work with Java 17.
- For JDBC applications, use the microtx-spring-boot-starter file.
```
<dependency>
     <groupId>com.oracle.microtx</groupId>
     <artifactId>microtx-spring-boot-starter</artifactId>
     <version>24.2</version>
</dependency>
```
- For Java Apps that use Hibernate as JPA provider, use the microtx-spring-boot-starter-hibernate library file.
```
<dependency>
     <groupId>com.oracle.microtx</groupId>
     <artifactId>microtx-spring-boot-starter-hibernate</artifactId>
     <version>24.2</version>
</dependency>
```
- For Java Apps that use EclipseLink as JPA provider, use the microtx-spring-boot-starter-eclipselink library file.
```
<dependency>
     <groupId>com.oracle.microtx</groupId>
     <artifactId>microtx-spring-boot-starter-eclipselink</artifactId>
     <version>24.2</version>
</dependency>
```
Import the com.oracle.microtx.common.MicroTxConfig package.
```
import com.oracle.microtx.common.MicroTxConfig;
```
Create a DataSourceInfo object for each resource manager. Ensure that you provide the data source names and resource manager IDs that you have the specified in the your application's YAML file.
Sample Command
```
DataSourceInfo departmentDataSourceInfo = new DataSourceInfo("ORCL1-8976-9776-9873");
departmentDataSourceInfo.setDataSourceName(departmentDataSource);

DataSourceInfo creditDataSourceInfo = new DataSourceInfo("ORCL2-2134-5668-8672");
creditDataSourceInfo.setDataSourceName(creditDataSource);
```
Where,
- departmentDataSource and creditDataSource are names of the XA data source that you have provided in your application's YAML file.
- ORCL1-8976-9776-9873 and ORCL2-2134-5668-8672 are the resource manager IDs that you have provided respectively for departmentDataSource and creditDataSource in your application's YAML file.
Later, you will use the @Inject annotation to ensure that your application uses these data sources.
Enter only one of the following MicroTx client library properties for each DataSourceInfo object that you have created. The following example provides property value for the creditDataSource object. Similarly, you can provide property values for other resource managers. If you don't provide any value, by default the resource is considered to be XA-compliant.
- For XA-compliant resources, enter:
```
creditDataSource.setXaSupport();
```
- For Oracle RAC database, enter:
```
creditDataSource.setRAC(true);
```
- For non-XA resources that use LLR optimization, enter:
```
creditDataSource.setLLRSupport();
```
- For non-XA resources that use LRC optimization, enter:
```
creditDataSource.setLRCSupport();
```
Initialize an XADatasource object. If you are using multiple resource managers with your application, initialize the XADatasource object in the following way for every XA-compliant resource manager.
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.MicroTxConfig
static void initXaDataSource(XADataSource dataSource, DataSourceInfo creditDataSource)
```
Where, creditDataSource is the DataSourceInfo object that you have previously created.

Repeat this step for every resource manager.

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
```
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.

Repeat this step for every resource manager.
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.MicroTxConfig.initXaDataSource(dataSource, creditDataSource)
```
Where, creditDataSource is the DataSourceInfo object that you have previously created.

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.

Repeat this step for every resource manager.

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.

If you are using multiple resource managers with your application, inject a connection object in the following way for every XA-compliant resource manager.

The following example describes how you can add two connections, one for each XA-compliant resource manager. When you inject the connection, call microTxSqlConnection followed by the name of your data source.

//Initialize the application context
private ApplicationContext applicationContext;
//Connection for XA-compliant resource manager 1
private Connection connection;
//Connection for XA-compliant resource manager 2
private Connection creditConnection;

@Autowired
    public AccountService(ApplicationContext applicationContext) {
        this.applicationContext = applicationContext;
        try {
            // Inject the connections for XA-compliant resource manager 1.
            // Specify the name of the data source associated with XA-compliant resource manager 1.            
            connection =  (Connection) applicationContext.getBean("microTxSqlConnection", "departmentDataSource");
            // Inject the connections for XA-compliant resource manager 2.
            // Specify the name of the data source associated with XA-compliant resource manager 2. 
            creditConnection =  (Connection) applicationContext.getBean("microTxSqlConnection","creditDataSource");
        } catch (ClassCastException ex) {
            LOG.info(ex.getMessage());
        }
   }

Where, creditDataSource is the value that you have provided for the dataSourceName string in the DataSourceInfo class of the oracle.tmm.jta.common.DataSourceInfo package.

Repeat this step for every resource manager.

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 = creditConnection.createStatement();
stmt1.execute(query);
stmt1.close();
```
Where, creditConnection 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 creditConnection object that is created by the MicroTx client library.

Repeat this step for every resource manager.
Save the changes.

If there are multiple Spring REST transaction participant services complete these steps for all the participant services.

Source code of a sample Spring REST transaction participant application which uses the MicroTx library and XA transaction protocol is available in the department-spring-multiplerm folder which is located in the microtx-samples GitHub repository. You can use this as a reference while integrating the MicroTx libraries with your application.

Parent topic: Configure Spring REST App as Transaction Participant