在使用AWS Neptune数据库时，我们可以使用以下代码示例来设置连接池：

import com.amazonaws.regions.Regions;
import com.amazonaws.services.neptune.AmazonNeptune;
import com.amazonaws.services.neptune.AmazonNeptuneClientBuilder;
import com.amazonaws.services.neptune.model.DBInstanceNotFoundException;

import java.util.Properties;

import org.apache.commons.dbcp2.BasicDataSource;

public class NeptuneConnectionPool {

    private BasicDataSource dataSource;

    public NeptuneConnectionPool(String endpoint, String port, String dbName, String username, String password, Regions region) throws Exception {
        dataSource = new BasicDataSource();

        dataSource.setUsername(username);
        dataSource.setPassword(password);
        dataSource.setUrl("jdbc:aws://" + endpoint + ":" + port + "/" + dbName + "?region=" + region.getName());
        dataSource.setDriverClassName("com.amazon.neptune.driver.GremlinDriver");

        // maximum number of active connections to allocate
        dataSource.setMaxTotal(20);

        // maximum number of connections to allow in the idle state
        dataSource.setMaxIdle(0);

        // minimum number of connections to allow in the idle state
        dataSource.setMinIdle(0);

        // maximum waiting time for an idle connection to become available
        dataSource.setMaxWaitMillis(10000);

        // validate connection before borrowing it from pool
        dataSource.setValidationQuery("SELECT 1");

        // check idle connection periodically
        dataSource.setTimeBetweenEvictionRunsMillis(60000);

        // validate idle connections during idle connection check
        dataSource.setTestWhileIdle(true);
    }

    public AmazonNeptune getConnection() throws DBInstanceNotFoundException {
        AmazonNeptune client = AmazonNeptuneClientBuilder.standard().withCredentials(new DefaultAWSCredentialsProviderChain()).build();
        client.describeDBInstances();
        client.shutdown();
        return client;
    }

    public BasicDataSource getDataSource() {
        return dataSource;
    }

    public void close() {
        try {
            dataSource.close();
        } catch (Exception e) {
        }
    }

}

其中，我们可以设置以下参数：

• dataSource.setMaxTotal(20)：连接池最大连接数
• dataSource.setMaxIdle(0)：最大空闲连接数
• dataSource.setMinIdle(0)：最小空闲连接数
• `dataSource.setMaxWaitMillis(100