MyBatis之SqlSessionFactory

本文主要是介绍MyBatis之SqlSessionFactory，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

MyBatis官方文档

MyBatis官方文档
ORM框架

范围和生命周期

SqlSessionFactory 一旦被创建就应该在应用的运行期间一直存在，没有任何理由对它进行清除或重建。使用 SqlSessionFactory 的最佳实践是在应用运行期间不要重复创建多次，多次重建 SqlSessionFactory 被视为一种代码“坏味道（bad smell）”。因此 SqlSessionFactory 的最佳范围是应用范围。有很多方法可以做到，最简单的就是使用单例模式或者静态单例模式。【摘自博文】

源码

package org.apache.ibatis.session;import java.sql.Connection;
/*** Creates an {@link SqlSession} out of a connection or a DataSource* @author Clinton Begin*/
public interface SqlSessionFactory {// 自动提交属性默认为falseSqlSession openSession();// 自定义自动提交属性SqlSession openSession(boolean autoCommit);SqlSession openSession(Connection connection);SqlSession openSession(TransactionIsolationLevel level);SqlSession openSession(ExecutorType execType);SqlSession openSession(ExecutorType execType, boolean autoCommit);SqlSession openSession(ExecutorType execType, TransactionIsolationLevel level);SqlSession openSession(ExecutorType execType, Connection connection);Configuration getConfiguration();}

实战

源码来自美团开源项目Leaf

package com.sankuai.inf.leaf.segment.dao.impl;import com.sankuai.inf.leaf.segment.dao.IDAllocDao;
import com.sankuai.inf.leaf.segment.dao.IDAllocMapper;
import com.sankuai.inf.leaf.segment.model.LeafAlloc;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.apache.ibatis.transaction.TransactionFactory;
import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;import javax.sql.DataSource;
import java.util.List;public class IDAllocDaoImpl implements IDAllocDao {SqlSessionFactory sqlSessionFactory;public IDAllocDaoImpl(DataSource dataSource) {TransactionFactory transactionFactory = new JdbcTransactionFactory();Environment environment = new Environment("development", transactionFactory, dataSource);Configuration configuration = new Configuration(environment);configuration.addMapper(IDAllocMapper.class);sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);}@Overridepublic List<LeafAlloc> getAllLeafAllocs() {// 设置自动提交属性为falseSqlSession sqlSession = sqlSessionFactory.openSession(false);try {// 查询不需要提交事务return sqlSession.selectList("com.sankuai.inf.leaf.segment.dao.IDAllocMapper.getAllLeafAllocs");} finally {// 关闭sqlSessionsqlSession.close();}}@Overridepublic LeafAlloc updateMaxIdAndGetLeafAlloc(String tag) {// 自动提交属性默认为falseSqlSession sqlSession = sqlSessionFactory.openSession();try {sqlSession.update("com.sankuai.inf.leaf.segment.dao.IDAllocMapper.updateMaxId", tag);LeafAlloc result = sqlSession.selectOne("com.sankuai.inf.leaf.segment.dao.IDAllocMapper.getLeafAlloc", tag);// 手动提交事务sqlSession.commit();return result;} finally {// 关闭sqlSessionsqlSession.close();}}@Overridepublic LeafAlloc updateMaxIdByCustomStepAndGetLeafAlloc(LeafAlloc leafAlloc) {SqlSession sqlSession = sqlSessionFactory.openSession();try {sqlSession.update("com.sankuai.inf.leaf.segment.dao.IDAllocMapper.updateMaxIdByCustomStep", leafAlloc);LeafAlloc result = sqlSession.selectOne("com.sankuai.inf.leaf.segment.dao.IDAllocMapper.getLeafAlloc", leafAlloc.getKey());sqlSession.commit();return result;} finally {sqlSession.close();}}@Overridepublic List<String> getAllTags() {SqlSession sqlSession = sqlSessionFactory.openSession(false);try {return sqlSession.selectList("com.sankuai.inf.leaf.segment.dao.IDAllocMapper.getAllTags");} finally {sqlSession.close();}}
}