Mybatis工作原理分析

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
public SqlSession openSession() {
  return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, false);
}
private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
  Transaction tx = null;
  try {
    final Environment environment = configuration.getEnvironment();
    final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
    tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
    final Executor executor = configuration.newExecutor(tx, execType);
    return new DefaultSqlSession(configuration, executor, autoCommit);
  } catch (Exception e) {
    closeTransaction(tx); // may have fetched a connection so lets call close()
    throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
  } finally {
    ErrorContext.instance().reset();
  }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
public int insert(String statement, Object parameter) {
  return update(statement, parameter);
}
public int update(String statement, Object parameter) {
  try {
    dirty = true;
    MappedStatement ms = configuration.getMappedStatement(statement);
    return executor.update(ms, wrapCollection(parameter));
  } catch (Exception e) {
    throw ExceptionFactory.wrapException("Error updating database.  Cause: " + e, e);
  } finally {
    ErrorContext.instance().reset();
  }
}

1
2
3
4
5
6
7
8
public int update(MappedStatement ms, Object parameter) throws SQLException {
  ErrorContext.instance().resource(ms.getResource()).activity("executing an update").object(ms.getId());
  if (closed) {
    throw new ExecutorException("Executor was closed.");
  }
  clearLocalCache();
  return doUpdate(ms, parameter);
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
public int doUpdate(MappedStatement ms, Object parameter) throws SQLException {
  Statement stmt = null;
  try {
    Configuration configuration = ms.getConfiguration();
    // 创建StatementHandler对象，从而创建Statement对象
    StatementHandler handler = configuration.newStatementHandler(this, ms, parameter, RowBounds.DEFAULT, null, null);
    // 将sql语句和参数绑定并生成SQL指令
    stmt = prepareStatement(handler, ms.getStatementLog());
    return handler.update(stmt);
  } finally {
    closeStatement(stmt);
  }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
public void commit() {
    this.commit(false);
}
public void commit(boolean force) {
  try {
      // 是否提交（判断是提交还是回滚）
      this.executor.commit(this.isCommitOrRollbackRequired(force));
      this.dirty = false;
  } catch (Exception var6) {
      throw ExceptionFactory.wrapException("Error committing transaction.  Cause: " + var6, var6);
  } finally {
      ErrorContext.instance().reset();
  }
}
//关闭自动提交且dirty=false（表示执行sql过程中无异常）
private boolean isCommitOrRollbackRequired(boolean force) {
    return !this.autoCommit && this.dirty || force;
}

//BaseExecutor的commit方法
public void commit(boolean required) throws SQLException {
  this.delegate.commit(required);
  this.tcm.commit();
}
//提交事物，清理本地缓存和刷新statement到数据库持久化存储
public void commit(boolean required) throws SQLException {
  if (this.closed) {
      throw new ExecutorException("Cannot commit, transaction is already closed");
  } else {
      this.clearLocalCache();
      this.flushStatements();
      if (required) {
          this.transaction.commit();
      }
  }
}
//最后调用JDBCTransaction的commit方法：
public void commit() throws SQLException {
  if (this.connection != null && !this.connection.getAutoCommit()) {
      if (log.isDebugEnabled()) {
          log.debug("Committing JDBC Connection [" + this.connection + "]");
      }
      // 提交连接
      this.connection.commit();
  }
}