From c004bbdf4f0e824e5ccbaef8f98ca4a3d44d3b49 Mon Sep 17 00:00:00 2001 From: wei <> Date: Fri, 14 Jul 2006 06:46:31 +0000 Subject: Changed SQLMap manual into a prado app. --- .../protected/pages/Manual/InheritanceMapping.page | 150 +++++++++++++++++++++ 1 file changed, 150 insertions(+) create mode 100644 demos/sqlmap-docs/protected/pages/Manual/InheritanceMapping.page (limited to 'demos/sqlmap-docs/protected/pages/Manual/InheritanceMapping.page') diff --git a/demos/sqlmap-docs/protected/pages/Manual/InheritanceMapping.page b/demos/sqlmap-docs/protected/pages/Manual/InheritanceMapping.page new file mode 100644 index 00000000..0458a291 --- /dev/null +++ b/demos/sqlmap-docs/protected/pages/Manual/InheritanceMapping.page @@ -0,0 +1,150 @@ + + +

Inheritance Mapping

+

The SQLMap PHP DataMapper supports the implementation +of object-oriented inheritance (subclassing) in your object model. There are +several developer options for mapping entity classes and subclasses to +database results:

+ +

You can use the most +efficient mapping strategies from a SQL and query performance perspective when +using the inheritance mappings of the DataMapper. To implement an inheritance +mapping, the resultMap must define one or more columns in your query's +resultset that will serve to identify which resultMap should be used to map +each result record to a specific subclass. In many cases, you will use one +column value for the DataMapper to use in identifying the proper resultMap and +subclass. This column is known as a discriminator.

+ +

For example, we have a table defined in a database that contains Document +records. There are five table columns used to store Document IDs, Titles, +Types, PageNumbers, and Cities. Perhaps this table belongs to a legacy +database, and we need to create an application using this table with a domain +model that defines a class hierarchy of different types of Documents. Or +perhaps we are creating a new application and database and just want to +persist the data found in a set of related classes into one table. In either +case, the DataMapper's inheritance mapping feature can help.

+ + +CREATE TABLE Documents ( + Document_ID int NOT NULL , + Document_Title varchar(32) NULL , + Document_Type varchar(32) NULL , + Document_PageNumber int NULL , + Document_City varchar(32) NULL +) + + +

To illustrate this, let's take a look at a few example classes shown below +that have a relationship through inheritance and whose properties can be +persisted into our Documents table. First, we have a base Document class that +has Id and Title properties. Next, we have a Book class that inherits from +Document and contains an additional property called PageNumber. Last, we have +a Newspaper class that also inherits from Document and contains a City +property.

+ + +class Document +{ + public $ID = -1; + public $Title = ''; +} + +class Book extends Document +{ + public $PageNumber = -1; +} + +class Newspaper extends Document +{ + public $City = ''; +} + + +

Now that we have our classes and database table, we can start working on our +mappings. We can create one <select> statement that returns all columns in the +table. To help the DataMapper discriminate between the different Document +records, we're going to indicate that the Document_Type column holds values +that will distinguish one record from another for mapping the results into our +class hierarchy.

+ + + + + + + + + + + + + + + + + + + + + +

The DataMapper compares the data found in the discriminator column to the +different <submap> values using the column value's string equivalence. Based +on this string value, SQLMap DataMapper will use the resultMap named "Book" or +"Newspaper" as defined in the <submap> elements or it will use the +"parent" resultMap "Document" if neither of the submap values satisfy the comparison. +With these resultMaps, we can implement an object-oriented inheritance mapping +to our database table.

+ +

If you want to use custom logic, you can use the typeHandler attribute of the +<discriminator> element to specify a custom type handler for the discriminator +column.

+ + + + + + + + + + + + +

The value of the typeHandler attribute specifies which of our classes +implements the ITypeHandlerCallback interface. This interface furnishes a +getResult method for coding custom logic to read the column result value and +return a value for the DataMapper to use in its comparison to the resultMap's +defined <submap> values.

+ + +class CustomInheritance implements ITypeHandlerCallback +{ + public function getResult($type) + { + if ($type=="Monograph" || $type=="Book") + return "Book"; + else if ($type=="Tabloid" || $type=="Broadsheet" || $type=="Newspaper") + return "Newspaper"; + else + return "Document"; + } + + public function getParameter($object) + { + throw new Exception('unimplemented'); + } + + public function createNewInstance() + { + throw new Exception('unimplemented'); + } +} + + + \ No newline at end of file -- cgit v1.2.3