Package io.odysz.semantic

Class DASemantics

java.lang.Object
io.odysz.semantic.DASemantics
Direct Known Subclasses:
DBSynmantics
public class DASemantics extends Object

The default table semantics plugin used by semantic-DA.

The DASemantext use this to manage semantics configuration for resolving data semantics.

DASemantics is basically a semantics handler, DASemantics.SemanticHandler 's container, with subclass handlers handling different semantics (processing values).

What's DASemantics for?

Well, the word semantics is a computer science term. The author don't want to redefine this word, but here is some explanation what semantic-DA with semantic-transact is trying to support.

In a typical relational database based application, the main operation of data is CRUD. And the most often such data operation can be abstracted to some operation pattern, and they are always organized as a database transaction/batch operation described in SQL.

Take "book-author" relation for example, the author's ID is also the parent referenced by book's author FK. If trying to delete an author in DB, there are 2 typical policies can be applied by the application. The first is delete all books by the author accordingly; the second is warning and denying the operation if some books are referencing the author. Both of this must/can been organized into a transact/batch operation, with the second transact as check-then-delete.

In this case, you will find the FK relationship can be handled in a generalized operation, through parameterizing some variables like table name, child referencing column name and parent ID.

Take the DASemantics.smtype.parentChildrenOnDel for example, it's automatically support "deleting all children when deleting parent" semantics. What the user (application developer) need to do is configure a semantics item then delete the parent directly.

Now you (a developer) will definitely understand what's the "parentChildrenOnDel" for. Semantic-DA abstract and hide these patterns, wrapped them automatically into a transaction. That's what semantic- DA want to do.

How to Use

To use this function:

1. Configure the "semantics.xml". See example in test/resources/semantics.xml.
2. Set the configured semantics as context of Statement. See example in io.odysz.semantic.DASemantextTest. Then use Statement's subclass's commit() method to generate SQLs

Is this Enough?

The 9 or 10 types of semantics defined in DASemantics.smtype is enough for some enterprise projects. It depends on how abstract the semantics we want to support. But it seems enough for us, at least now.

Another consideration is that semantic-DA never take supporting all semantics logic as it's goal. It's only trying to release burden of daily repeated tasks. Fortunately, such tasks' logic is simple, and the burden is heavy. Let semantic-* handle these simple logic, that's semantic-* designed for. If the semantics is complex, use anything you are familiar with. But in this case semantic-* are still useful to do this tasks, if users are familiar with the lower level API.

Before doing that, check the semantics-cheapflow workflow engine first, which is based on semantics-*, and can handle typical - not very cheap if by our define - logics all necessary for enterprise applications. It's a good example illustrating that if the semantics is designed carefully, those semantics supported by this pattern is enough.

But it do needs the application developers follow some design conventions. If you need you own semantics implementation, implement the interface ISemantext, or simply initialize Transcxt with null semantics, which will disable semantic supporting. In that way, it's working as a structured sql composing API.

Documents
Author:
odys-z@github.com

  • Field Details

    • ERR_CHK

      public static final String ERR_CHK
      error code key word
      See Also:

    • verbose

      public boolean verbose

    • basicTsx

      protected io.odysz.transact.sql.Transcxt basicTsx
      Static transact context for DB accessing without semantics support.
      Used to generate auto ID.

    • handlers

      protected ArrayList<DASemantics.SemanticHandler> handlers

    • tabl

      public final String tabl

  • Constructor Details

    • DASemantics

      public DASemantics(io.odysz.transact.sql.Transcxt basicTx, String tabl, String recId, boolean... verbose)
      Note: basicTx is already created per the connection, i. e. connect id is known.
      Parameters:
      basicTx -
      tabl -
      recId -
      verbose -

  • Method Details

    • replaceMeta

      public static io.odysz.semantics.meta.TableMeta replaceMeta(String tbl, io.odysz.semantics.meta.TableMeta m, String... connId) throws io.odysz.transact.x.TransException, SQLException
      Deprecated.
      since 2.0.0, to have a meta be the type of SemanticTableMeta, configure the class name in semantics.xml/t[id=metas], instead of calling this method.
      Use this to replace metas from DB for semantics extension.
      Parameters:
      tbl -
      m -
      connId -
      Returns:
      replaced meta
      Throws:
      io.odysz.transact.x.TransException
      SQLException
      Since:
      1.4.25

    • addHandler

      public DASemantics addHandler(DASemantics.SemanticHandler h)

    • addHandler

      public void addHandler(DASemantics.smtype semantic, String tabl, String recId, String[] args) throws Exception
      Throws:
      Exception

    • handler

      public DASemantics.SemanticHandler handler(DASemantics.smtype sm)

    • createSMap

      public DATranscxt.SemanticsMap createSMap(String conn)

    • parseHandler

      public DASemantics.SemanticHandler parseHandler(io.odysz.transact.sql.Transcxt trb, String tabl, DASemantics.smtype semantic, String recId, String[] args) throws Exception
      Throws:
      Exception

    • has

      public boolean has(DASemantics.smtype sm)

    • onInsert

      public void onInsert(io.odysz.semantics.ISemantext semantx, io.odysz.transact.sql.Insert statemt, ArrayList<Object[]> row, Map<String,Integer> cols, io.odysz.semantics.IUser usr) throws io.odysz.transact.x.TransException
      Throws:
      io.odysz.transact.x.TransException

    • onUpdate

      public void onUpdate(io.odysz.semantics.ISemantext semantx, io.odysz.transact.sql.Update satemt, ArrayList<Object[]> row, Map<String,Integer> cols, io.odysz.semantics.IUser usr) throws io.odysz.transact.x.TransException
      Throws:
      io.odysz.transact.x.TransException

    • onDelete

      public void onDelete(io.odysz.semantics.ISemantext semantx, io.odysz.transact.sql.Delete stmt, io.odysz.transact.sql.parts.condition.Condit whereCondt, io.odysz.semantics.IUser usr) throws io.odysz.transact.x.TransException
      Throws:
      io.odysz.transact.x.TransException

    • onPost

      public void onPost(io.odysz.semantics.ISemantext sx, io.odysz.transact.sql.Statement<? extends io.odysz.transact.sql.Statement<?>> stmt, ArrayList<Object[]> row, Map<String,Integer> cols, io.odysz.semantics.IUser usr, ArrayList<String> sqlBuf) throws SemanticException
      Throws:
      SemanticException

    • requiredNv

      public static Object[] requiredNv(String n, io.odysz.transact.sql.parts.AbsPart v, Map<String,Integer> cols, ArrayList<Object[]> row, String target, io.odysz.semantics.IUser usr)
      Force to set or extend a nv pair into row
      Parameters:
      n - forced field
      v - forced value
      cols -
      row - row to be expanded
      target - for the table
      usr - operator
      Returns:
      the extended or forced value's nv pair

    • clone

      public DASemantics clone()
      Shallow copy, with new list of handlers, with each elements referring to the original one.
      Overrides:
      clone in class Object