MyBatis核心对象之StatementHandler

StatementHandler ResultHandler ParameterHandler Executor

org.apache.ibatis.executor.statement.StatementHandler
org.apache.ibatis.session.ResultHandler
org.apache.ibatis.executor.parameter.ParameterHandler
org.apache.ibatis.executor.Executor

public interface StatementHandler {
    //获取语句
    Statement prepare(Connection connection, Integer transactionTimeout)
        throws SQLException;
    //设置参数
    void parameterize(Statement statement)
        throws SQLException;
    //操作
    void batch(Statement statement)
        throws SQLException;
    //操作
    int update(Statement statement)
        throws SQLException;
    //操作
    <E> List<E> query(Statement statement, ResultHandler resultHandler)
        throws SQLException;
    //操作
    <E> Cursor<E> queryCursor(Statement statement)
        throws SQLException;
    //获取BoundSql
    BoundSql getBoundSql();
    //获取参数处理器
    ParameterHandler getParameterHandler();
}

public class RoutingStatementHandler implements StatementHandler {

    private final StatementHandler delegate;

    //核心，根据ms的语句类型来创建相应的StatementHandler
    public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {

        switch (ms.getStatementType()) {
            case STATEMENT:
                delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
                break;
            case PREPARED:
                delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
                break;
            case CALLABLE:
                delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
                break;
            default:
                throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
        }

    }

    @Override
    public Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException {
        return delegate.prepare(connection, transactionTimeout);
    }

    @Override
    public void parameterize(Statement statement) throws SQLException {
        delegate.parameterize(statement);
    }

    @Override
    public void batch(Statement statement) throws SQLException {
        delegate.batch(statement);
    }

    @Override
    public int update(Statement statement) throws SQLException {
        return delegate.update(statement);
    }

    @Override
    public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
        return delegate.query(statement, resultHandler);
    }

    @Override
    public <E> Cursor<E> queryCursor(Statement statement) throws SQLException {
        return delegate.queryCursor(statement);
    }

    @Override
    public BoundSql getBoundSql() {
        return delegate.getBoundSql();
    }

    @Override
    public ParameterHandler getParameterHandler() {
        return delegate.getParameterHandler();
    }
}

@startuml
interface StatementHandler
class RoutingStatementHandler

StatementHandler <|.. RoutingStatementHandler

abstract class BaseStatementHandler
class PreparedStatementHandler
class CallableStatementHandler
class SimpleStatementHandler

StatementHandler <|.. BaseStatementHandler
BaseStatementHandler <|-- PreparedStatementHandler
BaseStatementHandler <|-- CallableStatementHandler
BaseStatementHandler <|-- SimpleStatementHandler
@enduml