說明

前面二看到了 sqlSession最終是找到MapperStatement然後委托給Executer執行的 Executer到底做了什麽

接口定義

public interface Executor {
    ResultHandler NO_RESULT_HANDLER = null;

    int update(MappedStatement var1, Object var2) throws SQLException;

    <E> List<E> query(MappedStatement var1, Object var2, RowBounds var3, ResultHandler var4, CacheKey var5, BoundSql var6) throws
 
 SQLException;

    <E> List<E> query(MappedStatement var1, Object var2, RowBounds var3, ResultHandler var4) throws SQLException;

    <E> Cursor<E> queryCursor(MappedStatement var1, Object var2, RowBounds var3) throws SQLException;

    List<BatchResult> flushStatements() throws
 
 SQLException;

    void commit(boolean var1) throws SQLException;

    void rollback(boolean var1) throws SQLException;

    CacheKey createCacheKey(MappedStatement var1, Object var2, RowBounds var3, BoundSql var4);

    boolean isCached(MappedStatement var1, CacheKey var2);

    void clearLocalCache();

    
 
void deferLoad(MappedStatement var1, MetaObject var2, String var3, CacheKey var4, Class<?> var5);

    Transaction getTransaction();

    void close(boolean var1);

    boolean isClosed();

    void setExecutorWrapper(Executor var1);
}

類圖

Executor各個實現

ClosedExecutor

org.apache.ibatis.executor.loader.ResultLoaderMap 中的一個內部靜態類

 private static final class ClosedExecutor extends BaseExecutor {
        public ClosedExecutor() {
            super((Configuration)null, (Transaction)null);
        }

        public boolean isClosed() {
            return true;
        }

        protected int doUpdate(MappedStatement ms, Object parameter) throws SQLException {
            throw new UnsupportedOperationException("Not supported.");
        }

        protected List<BatchResult> doFlushStatements(boolean isRollback) throws SQLException {
            throw new UnsupportedOperationException("Not supported.");
        }

        protected <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
            throw new UnsupportedOperationException("Not supported.");
        }

        protected <E> Cursor<E> doQueryCursor(MappedStatement ms, Object parameter, RowBounds rowBounds, BoundSql boundSql) throws SQLException {
            throw new UnsupportedOperationException("Not supported.");
        }
    }

沒有具體實現 我們不會用到

SimpleExecutor

每執行一次update或select，就開啟一個Statement對象，用完立刻關閉Statement對象。（可以是Statement或PrepareStatement對象）

public class SimpleExecutor extends BaseExecutor {
    public int doUpdate(MappedStatement ms, Object parameter) throws SQLException {
        Statement stmt = null;

        int var6;
        try {
            //獲得configuration
            Configuration configuration = ms.getConfiguration();
            //根據configuration獲得對應的StatementHandler 後面講
            StatementHandler handler = configuration.newStatementHandler(this, ms, parameter, RowBounds.DEFAULT, (ResultHandler) null, (BoundSql) null);
            stmt = this.prepareStatement(handler, ms.getStatementLog());
            var6 = handler.update(stmt);
        } finally {
            //釋放Statement
            this.closeStatement(stmt);
        }

        return var6;
    }
    private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
        Connection connection = this.getConnection(statementLog);
        Statement stmt = handler.prepare(connection, this.transaction.getTimeout());
        handler.parameterize(stmt);
        return stmt;
    }
}

可以看到finally會關閉Statement

mybatis源碼閱讀-執行器Executor(四)