Mybatis源码之Statement处理器BaseStatementHandler（二）

/**
* @author Clinton Begin
*/
public abstract class BaseStatementHandler implements StatementHandler {

protected final Configuration configuration;
protected final ObjectFactory objectFactory;
protected final TypeHandlerRegistry typeHandlerRegistry;
protected final ResultSetHandler resultSetHandler;
protected final ParameterHandler parameterHandler;

protected final Executor executor;
protected final MappedStatement mappedStatement;
protected final RowBounds rowBounds;

protected BoundSql boundSql;

protected BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
this.configuration = mappedStatement.getConfiguration();
this.executor = executor;
this.mappedStatement = mappedStatement;
this.rowBounds = rowBounds;

this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
this.objectFactory = configuration.getObjectFactory();

if (boundSql == null) { // issue #435, get the key before calculating the statement
generateKeys(parameterObject);
boundSql = mappedStatement.getBoundSql(parameterObject);
}

this.boundSql = boundSql;

this.parameterHandler = configuration.newParameterHandler(mappedStatement, parameterObject, boundSql);
this.resultSetHandler = configuration.newResultSetHandler(executor, mappedStatement, rowBounds, parameterHandler, resultHandler, boundSql);
}
//获取BoundSql
public BoundSql getBoundSql() {
return boundSql;
}
//获取ParameterHandler
public ParameterHandler getParameterHandler() {
return parameterHandler;
}

//准备语句
public Statement prepare(Connection connection) throws SQLException {
ErrorContext.instance().sql(boundSql.getSql());
Statement statement = null;
try {
//实例化Statement
statement = instantiateStatement(connection);
//设置超时
setStatementTimeout(statement);
//设置读取条数
setFetchSize(statement);
return statement;
} catch (SQLException e) {
closeStatement(statement);
throw e;
} catch (Exception e) {
closeStatement(statement);
throw new ExecutorException("Error preparing statement.  Cause: " + e, e);
}
}
//如何实例化Statement，交给子类去做
protected abstract Statement instantiateStatement(Connection connection) throws SQLException;

//设置超时，实际就是调用Statement.setQueryTimeout
protected void setStatementTimeout(Statement stmt) throws SQLException {
Integer timeout = mappedStatement.getTimeout();
Integer defaultTimeout = configuration.getDefaultStatementTimeout();
if (timeout != null) {
stmt.setQueryTimeout(timeout);
} else if (defaultTimeout != null) {
stmt.setQueryTimeout(defaultTimeout);
}
}
//设置读取条数，其实就是调用Statement.setFetchSize
protected void setFetchSize(Statement stmt) throws SQLException {
Integer fetchSize = mappedStatement.getFetchSize();
if (fetchSize != null) {
stmt.setFetchSize(fetchSize);
}
}
//关闭Statement
protected void closeStatement(Statement statement) {
try {
if (statement != null) {
statement.close();
}
} catch (SQLException e) {
//ignore
}
}

protected void generateKeys(Object parameter) {
KeyGenerator keyGenerator = mappedStatement.getKeyGenerator();
ErrorContext.instance().store();
keyGenerator.processBefore(executor, mappedStatement, null, parameter);
ErrorContext.instance().recall();
}

}