Java Database Connectivity (JDBC)

I have an existing spring Boot 2.6.2 microservice that we want to add a call to a new data source. This is being Deployed to Openliberty 23.0.0.10 with Java 8. I created a new DAO:

public class iSeriesDatabaseDao {
      @Autowired
      private JdbcTemplate jdbcTemplate;
      public String getPhoneNumber(String number)
                                   throws SSOServiceException {
               try {
                      String sqlString = String.join(" ",
                           "SELECT phone AS SPECIALITY, (wrkph1 CONCAT wrkph2 CONCAT wrkph3) AS PHONE FROM PRVMAS where PROVNO = '%s'");
                      String getPhone = String.format(sqlString,number);
                      return String.valueOf(jdbcTemplate.queryForList(getPhone));
                  } catch (Exception e) {
                        throw new SSOServiceException("Error in the query the 
                  configuration table: " + e.getMessage());
                 }
             }

I have updated my server.xml file for my website apkbeb to account for the new JDBC driver and data source connection.

             <jdbcDriver id="DB2iSeries">
                            <library name="DB2iToolboxLib">
                                          <fileset dir="${wlp.user.dir}/shared/resources" includes="jt400.jar" />
                            </library>
             </jdbcDriver>
<dataSource jdbcDriverRef="DB2iSeries" jndiName="jdbc/iSeriesDataSource">
   <properties serverName="${env.DB_ISERIES_URL}" password="${env.DB_ISERIES_PWD}" user="${env.DB_USERID}" />
</dataSource>

I also updated my application.properties file too.

spring.datasource.jndi-name=jdbc/PostgresSQLDataSource
spring.datasource.jndi-name-iSeries=jdbc/iSeriesDataSource

I am getting the following error message when I test my code.

[ERROR   ] Connection error:
SSL error: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[ERROR   ] Failed to create a ConnectionPoolDataSource from PostgreSQL JDBC Driver 42.1.4 for user_xxx at jdbc:postgresql://Dev.xxx.com:3306/xxx?prepareThreshold=5&preparedStatementCacheQueries=256&preparedStatementCacheSizeMiB=5&databaseMetadataCacheFields=65536&databaseMetadataCacheFieldsMiB=5&defaultRowFetchSize=0&binaryTransfer=true&readOnly=false&binaryTransferEnable=&binaryTransferDisable=&unknownLength=2147483647&logUnclosedConnections=false&disableColumnSanitiser=false&ssl=true&tcpKeepAlive=false&loginTimeout=0&connectTimeout=10&socketTimeout=0&cancelSignalTimeout=10&receiveBufferSize=-1&sendBufferSize=-1&ApplicationName=PostgreSQL JDBC Driver&useSpnego=false&gsslib=auto&sspiServiceClass=POSTGRES&allowEncodingChanges=false&targetServerType=any&loadBalanceHosts=false&hostRecheckSeconds=10&preferQueryMode=extended&autosave=never&reWriteBatchedInserts=false: org.postgresql.util.PSQLException: SSL error: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
             at org.postgresql.ssl.MakeSSL.convert(MakeSSL.java:67)
             at org.postgresql.core.v3.ConnectionFactoryImpl.enableSSL(ConnectionFactoryImpl.java:359)
             at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:148)
             at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
             at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:194)
             at org.postgresql.Driver.makeConnection(Driver.java:450)

This references the PostgreSQL database which is an existing connection, not my new connection. The PostgreSQL connection is working fine. What additional changes are needed to set up the new iSeries connection?