SqlMapClientImpl拥有SqlMapExecutorDelegate,ThreadLocal两个对象。还有getLocalSqlMapSession(),openSession()和insert(),update,delete(),queryForObject()几个方法。代码:
public SqlMapExecutorDelegate delegate; protected ThreadLocal localSqlMapSession = new ThreadLocal(); public SqlMapSession openSession() { SqlMapSessionImpl sqlMapSession = new SqlMapSessionImpl(this); sqlMapSession.open(); return sqlMapSession; } public SqlMapSession openSession(Connection conn) { try { SqlMapSessionImpl sqlMapSession = new SqlMapSessionImpl(this); sqlMapSession.open(); sqlMapSession.setUserConnection(conn); return sqlMapSession; } catch (SQLException e) { throw new SqlMapException("Error setting user provided connection. Cause: " + e, e); } } protected SqlMapSessionImpl getLocalSqlMapSession() { SqlMapSessionImpl sqlMapSession = (SqlMapSessionImpl) localSqlMapSession.get(); if (sqlMapSession == null || sqlMapSession.isClosed()) { sqlMapSession = new SqlMapSessionImpl(this); localSqlMapSession.set(sqlMapSession); } return sqlMapSession; } public Object insert(String id, Object param) throws SQLException { return getLocalSqlMapSession().insert(id, param); } public int update(String id, Object param) throws SQLException { return getLocalSqlMapSession().update(id, param); } public int delete(String id, Object param) throws SQLException { return getLocalSqlMapSession().delete(id, param); } public Object queryForObject(String id, Object paramObject) throws SQLException { return getLocalSqlMapSession().queryForObject(id, paramObject); }
不难看出SqlMapClientImpl拥有多个SqlMapSessionImpl(它们隶属于不同线程,通过localSqlMapSession 来管理)。
而其中的insert(),update(),delete(),queryForObject()将委托给SqlMapSessionImpl。
那在看看SqlMapSessionImpl部分代码:
protected SqlMapExecutorDelegate delegate; protected SessionScope sessionScope; public SqlMapSessionImpl(SqlMapClientImpl client) { this.delegate = client.getDelegate(); this.sessionScope = this.delegate.beginSessionScope(); this.sessionScope.setSqlMapClient(client); this.sessionScope.setSqlMapExecutor(client); this.sessionScope.setSqlMapTxMgr(client); this.closed = false; } public Object insert(String id, Object param) throws SQLException { return delegate.insert(sessionScope, id, param); } public int update(String id, Object param) throws SQLException { return delegate.update(sessionScope, id, param); } public int delete(String id, Object param) throws SQLException { return delegate.delete(sessionScope, id, param); } public Object queryForObject(String id, Object paramObject) throws SQLException { return delegate.queryForObject(sessionScope, id, paramObject); }
首先是构造函数,它将初始化一些信息,注意this.delegate = client.getDelegate();说明SqlMapClientImpl,SqlMapSessionImpl所使用的是同一个SqlMapExecutorDelegate。
而它的insert(),update,delete(),queryForObject()这几个方法将委托给SqlMapExecutorDelegate。
看看SqlMapExecutorDelegate代码(只是部分代码,没有贴全):
protected SqlExecutor sqlExecutor; public int update(SessionScope sessionScope, String id, Object param) throws SQLException { int rows = 0; MappedStatement ms = getMappedStatement(id); Transaction trans = getTransaction(sessionScope); boolean autoStart = trans == null; try { trans = autoStartTransaction(sessionScope, autoStart, trans); StatementScope statementScope = beginStatementScope(sessionScope, ms); try { rows = ms.executeUpdate(statementScope, trans, param); } finally { endStatementScope(statementScope); } autoCommitTransaction(sessionScope, autoStart); } finally { autoEndTransaction(sessionScope, autoStart); } return rows; }
SqlMapExecutorDelegate将做些事务控制,从代码rows = ms.executeUpdate(statementScope, trans, param);可以看出之后将具体操作委托给MappedStatement。
继续跟下去,看下MappedStatement的相关代码:
public int executeUpdate(StatementScope statementScope, Transaction trans, Object parameterObject) throws SQLException { ErrorContext errorContext = statementScope.getErrorContext(); errorContext.setActivity("preparing the mapped statement for execution"); errorContext.setObjectId(this.getId()); errorContext.setResource(this.getResource()); statementScope.getSession().setCommitRequired(true); try { parameterObject = validateParameter(parameterObject); Sql sql = getSql(); errorContext.setMoreInfo("Check the parameter map."); ParameterMap parameterMap = sql.getParameterMap(statementScope, parameterObject); errorContext.setMoreInfo("Check the result map."); ResultMap resultMap = sql.getResultMap(statementScope, parameterObject); statementScope.setResultMap(resultMap); statementScope.setParameterMap(parameterMap); int rows = 0; errorContext.setMoreInfo("Check the parameter map."); Object[] parameters = parameterMap.getParameterObjectValues(statementScope, parameterObject); errorContext.setMoreInfo("Check the SQL statement."); String sqlString = sql.getSql(statementScope, parameterObject); errorContext.setActivity("executing mapped statement"); errorContext.setMoreInfo("Check the statement or the result map."); rows = sqlExecuteUpdate(statementScope, trans.getConnection(), sqlString, parameters);// important errorContext.setMoreInfo("Check the output parameters."); if (parameterObject != null) { postProcessParameterObject(statementScope, parameterObject, parameters); } errorContext.reset(); sql.cleanup(statementScope); notifyListeners(); return rows; } catch (SQLException e) { errorContext.setCause(e); throw new NestedSQLException(errorContext.toString(), e.getSQLState(), e.getErrorCode(), e); } catch (Exception e) { errorContext.setCause(e); throw new NestedSQLException(errorContext.toString(), e); } } protected int sqlExecuteUpdate(StatementScope statementScope, Connection conn, String sqlString, Object[] parameters) throws SQLException { if (statementScope.getSession().isInBatch()) { getSqlExecutor().addBatch(statementScope, conn, sqlString, parameters); return 0; } else { return getSqlExecutor().executeUpdate(statementScope, conn, sqlString, parameters); } } public SqlExecutor getSqlExecutor() { return sqlMapClient.getSqlExecutor(); }
哦,executeUpdate(StatementScope statementScope, Transaction trans, Object parameterObject)中的
rows = sqlExecuteUpdate(statementScope, trans.getConnection(), sqlString, parameters);将调用
sqlExecuteUpdate(StatementScope statementScope, Connection conn, String sqlString, Object[] parameters),
而sqlExecuteUpdate(StatementScope statementScope, Connection conn, String sqlString, Object[] parameters)
将调用SqlExecutor的executeUpdate来进行具体操作。而这个SqlExecutor是来自SqlMapExecutorDelegate的。
所以我们在做ibatis分页的时候可以通过反射向SqlMapExecutorDelegate强制注入自定义的SqlExecutor来达到分页效果。