博客

01.openSession到底做了什么

1.1 SqlSessionFactory 接口的方法，得找接口的实现类

1.2DefaultSqlSessionFactory implements SqlSessionFactory

进而找到了DefaultSqlSessionFactory 的openSession（）,openSession方法的原型如下：

public SqlSession openSession() {
    return this.openSessionFromDataSource(this.configuration.getDefaultExecutorType(), (TransactionIsolationLevel)null, false);
}

1.3openSessionFromDataSource方法原型如下：

private


SqlSession openSessionFromDataSource(ExecutorTypeexecType, TransactionIsolationLevel level,


boolean


autoCommit){

Transaction tx =


null


;

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

    return var8;
}

1.4DefaultSqlSession方法原型如下

public DefaultSqlSession(Configuration configuration, Executor executor) {
    this.configuration = configuration;
    this.executor = executor;
    this.dirty = false;
}

02.insert和delete底层到底是什么？

Session.insert(“xxx”)

public int insert(String statement) {
    return this.insert(statement, (Object)null);//调度2个参数的insert
}

public int insert(String statement, Object parameter) {
    return this.update(statement, parameter);//底层调用update
}

03.为什么session.commit（）引起事务的提交？

session.commit（）；

最终调度到事务的commit

this.transaction.commit（）；

04.session.close（）为什么可以回滚事务

1.从session.insert（）开始

public int insert(String statement, Objectparameter) {

return this.update(statement, parameter);

}

—>update

publicint update(String statement, Object parameter) {

this.dirty = true;//注意这里将dirty设置成真，内存数据和DB数据库数据不一致

MappedStatement e = this.configuration.getMappedStatement(statement);

}

session.close()

this.executor.close(this.isCommitOrRollbackRequired(false));

——>isCommitOrRollbackRequired

privateboolean isCommitOrRollbackRequired(boolean force) {

return this.dirty || force;  //这里得到的是true

}

——>Executor的close（）

public void close(boolean forceRollback) {

this.rollback(forceRollback);//true

}

——>rollback

public void rollback(boolean required)throws SQLException {

if(required) {

this.transaction.rollback();

}

}