[Original] oop programming ibatis learning notes four-table join query expression

The classes of the two tables are shown in the previous article.<2Table join queries>

Here we will discuss how to use our habits.Inner joinOfSQLStatement to associate our data tables

 

The only difference is that

Book. xml

 

< Resultmap ID = "Get-book-Note" Class = "Com. It. Book" Groupby = "Book. oid" >
< Result Property = "Oid" Column = "Oid" />
< Result Property = "Name" Column = "Name" />
< Result Property = "Notes" Resultmap = "Get-Note"   />
</ Resultmap >

< Resultmap ID = "Get-Note" Class = "NOTE" >
< Result Property = "Sid" Column = "Sid"   />
< Result Property = "Sname" Column = "Sname"   />
</ Resultmap >

<SelectID= "Getproduct"Resultmap= "Get-book-Note">
 <! [CDATA [ 

Select

Book. OID,

Book. Name,

Note. Sid,

Note. sname

From

Book, note where note. book_oid = book. OID

 ]> 
</Select>

 

Notes: 1. SQLAll fields in the statement,All must be inResultmapEmbodied in,Otherwise, the queried fields areNULL;

2.Parent table associated with child table,Add

<Result Property="Notes" Resultmap="Get-Note" />

property Notes attributes and methods to obtain subclasses , the result must be a subclass resultmap id

3. SelectStatementResultmapCorresponds toResultmapName

 

Test statement'Main. Java

 

// Test the association between two tables. Author: meetweb Try {
Book book1 = New Book ();
Book1.setoid (1 );
List <book> books = sqlmapclinet. queryforlist ("getproduct ");
System. Out. println (books. Size ());
For (Iterator = books. iterator (); iterator. hasnext ();){
Book bookk = (book) iterator. Next ();
System. Out. println (bookk. getname ());
List <Note> L = bookk. getnotes ();
System. Out. println (Note) L. Get (0). getsname ());
}
} Catch (Sqlexception e ){
// Todo auto-generated Catch Block
E. printstacktrace ();
}

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