MyBatis openSession(), close(), and commit() usage explanation

1: What exactly does openSession do in the MyBatis tool class?

Mybatis Tool Class

 1     private static final String RESOURCE = "mybatis-config.xml"; 2     private static SqlSessionFactory sqlSessionFactory = null; 3     private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>(); 4  5  6  7  8     //关闭sqlsession 9     public static void closeSession(){10         SqlSession session = (SqlSession) threadLocal.get(); // 211         threadLocal.set(null);12         if (session !=null){13             session.close();14         }15     }16 17     public static SqlSession getSessionTwo() {18         //读取配置文件19         try {20             InputStream stream = Resources.getResourceAsStream(RESOURCE);21             sqlSessionFactory = new SqlSessionFactoryBuilder().build(stream);22 23             return sqlSessionFactory.openSession();   //返回openSession24         } catch (IOException e) {25             e.printStackTrace();26         }27 28         return null;29     }

First click openSession to find a way to use sqlsessionFactory

 1 package org.apache.ibatis.session; 2  3 import java.sql.Connection; 4  5 public interface SqlSessionFactory { 6     SqlSession openSession(); 7  8     SqlSession openSession(boolean var1); 9 10     SqlSession openSession(Connection var1);

Then look at the implementation class of this method DefaultSqlSessionFactory

Here mainly returns a method of his own class openSessionFroDataSource() (data source) and assigns autoCommit to false

Then enter this method

 private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
        Transaction tx = null;

        DefaultSqlSession var8;try {
            Environment environment = this.configuration.getEnvironment();
            TransactionFactory transactionFactory = this.getTransactionFactoryFromEnvironment(environment);
            tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
            Executor executor = this.configuration.newExecutor(tx, execType);
            var8 = new DefaultSqlSession(this.configuration, executor, autoCommit);
        } catch (Exception var12) {this.closeTransaction(tx);throw ExceptionFactory.wrapException("Error opening session.  Cause: " + var12, var12);
        } finally {
            ErrorContext.instance().reset();
        }return var8;
    }

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可以看到他这个方法主要是初始化一些configure.xml的配置信息和DefaultSqlSession

configure.xml的配置信息和DefaultSqlSession

2: Why does the bottom layer of sqlSession.close() in the MyBatis tool class roll back the transaction?

First enter close() to find its implementation class DefaultsqlSession

The close method in DefaultsqlSession

 

##In addition, as for why close will roll back the transaction before it is submitted, and it will close the transaction after it is submitted

It mainly depends on the implementation class BaseExecutor of Executor

session.close(); 底层为什么可以回滚事务？？？？？<br>DefaultsqlSession里的close方法<br>

session.commit(); Why can the transaction be submitted? Its implementation is basically the same as the implementation of close(). The main reason is

 public void close() {try {this.executor.close(this.isCommitOrRollbackRequired(false));this.dirty = false;
        } finally {
            ErrorContext.instance().reset();
        }

    }

The parameter is true or false. Submit, then close

session

    
 进入Executor接口  查看他的实现类BaseExecutor 找到close()方法<br>

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