我使用hibernate+springboot，db是mysql，两天后就有了从150到250的大量连接。这是我的bean，它与实体和db交互。我想我会处理所有的异常并关闭所有的连接

package com.root.lvrmmonitor.utils;

import com.root.lvrmmonitor.entities.*;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class DBManager {

    public List<Item> getItemsList() {

        try (Session session = HibernateUtil.getSessionFactory().openSession()) {
            return session.createQuery("from Item", Item.class).list();
        }
    }

    public DropTarget saveDropTarget(DropTarget dropTarget) {

        try (Session session = HibernateUtil.getSessionFactory().openSession()) {
            Transaction tx = session.beginTransaction();
            session.save(dropTarget);
            tx.commit();
        }

        return dropTarget;
    }

    public void deleteDropTarget(DropTarget dropTarget) {
        try (Session session = HibernateUtil.getSessionFactory().openSession()) {
            Transaction tx = session.beginTransaction();
            session.delete(dropTarget);
            tx.commit();
        }
    }

    public void saveSuccess(Success success) {

        try (Session session = HibernateUtil.getSessionFactory().openSession()) {
            Transaction tx = session.beginTransaction();
            session.save(success);
            tx.commit();
        }
    }
}