Simple to say, programmer can use the same JNDI interface to query the following

• lookup resources provided by application server, such as data source
• search LDAP entries
• lookup DNS records

Brief introduction is here.

The code

Resources of the application server are placed under "java:comp/env" prefix. Assume that a data source is on

java:/comp/env/jdbc/db1

To get that data source

javax.naming.Context initialContext = new javax.naming.InitialContext();
javax.naming.Context subContext = (javax.naming.Context) initialContext.lookup("java:comp/env");
DataSource dataSource = (DataSource) subContext.lookup("jdbc/db1");

Or you may get the instance directly by providing the full path

javax.naming.Context initialContext = new javax.naming.InitialContext();
DataSource dataSource = (DataSource) initialContext.lookup("java:comp/env/jdbc/db1");

Spring boot integration

Just add a line into application.properties

spring.datasource.jndi-name=java:/comp/env/jdbc/db1

The related bean is created by org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration

@Configuration(proxyBeanMethods = false)
@AutoConfigureBefore({ XADataSourceAutoConfiguration.class, DataSourceAutoConfiguration.class })
@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
@ConditionalOnProperty(prefix = "spring.datasource", name = "jndi-name")
@EnableConfigurationProperties(DataSourceProperties.class)
public class JndiDataSourceAutoConfiguration {

    @Bean(destroyMethod = "")
    @ConditionalOnMissingBean
    public DataSource dataSource(DataSourceProperties properties, ApplicationContext context) {
        JndiDataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
        DataSource dataSource = dataSourceLookup.getDataSource(properties.getJndiName());
        excludeMBeanIfNecessary(dataSource, "dataSource", context);
        return dataSource;
    }

    private void excludeMBeanIfNecessary(Object candidate, String beanName, ApplicationContext context) {
        for (MBeanExporter mbeanExporter : context.getBeansOfType(MBeanExporter.class).values()) {
            if (JmxUtils.isMBean(candidate.getClass())) {
                mbeanExporter.addExcludedBean(beanName);
            }
        }
    }

}