net.as_development.asdk.db_service.impl

Class NextToken

java.lang.Object

net.as_development.asdk.db_service.impl.NextToken

public class NextToken
extends Object

Handle all around paging and next token (if such token can be implemented using offset and page size values). Queries can have to much results. At least paging can help. But then following queries has to use offset and limit ... and has to know where last result page was finished and new one has to begin. The BD layer knows the paradigm of the next-token serialized as a string. It's up to the code to know which information are coded into such next token ... the code using the DB layer transport such token to the client and back. How an instance of this class has to be used:

  
   public String queryRows(Row             aMeta     ,
                           String          sNextToken,
                           List< Row >     lResults  ,
                           IDBBackendQuery iQuery    )
       throws Exception
   {
       ....

       // parse the given token and retrieve its information
       // as e.g. offset and page size
       NextToken4Offset aNextToken = new NextToken4Offset   (sNextToken);
       int              nOffset    = aNextToken.getOffset   ();
       int              nPageSize  = aNextToken.getPageSize ();
       
       // use such informations to start new query.
       Results aResult = impl_doQuery (..., nOffset, nPageSize);
       
       // 'max results' must count ALL possible results of a query
       // independent how many items was used from that results set ! 
       int nMaxResults = aResult.getCount ();

       // pass max count of results to the token instance and
       // let it calculate the next possible token ...
       // The return value of those call will be the next sNextToken
       // passed to this query method then.
       // If method return an empty string no further results exists and
       // no further query makes sense.
       return aNextToken.stepNext (nMaxResults);
   }
  
  

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_OFFSET
static int	DEFAULT_PAGESIZE
static String	NO_NEXT_TOKEN
static String	PROP_OFFSET
static String	PROP_PAGESIZE
static String	SEPARATOR

Constructor Summary

Constructors

Constructor and Description
NextToken()
NextToken(String sToken)

Method Summary

Modifier and Type	Method and Description
String	asString()
String	finish()
int	getOffset()
int	getPageSize()
void	parse(String sToken) parse the given token and fill this instance.
void	setOffset(int nOffset) set the new offset for the next token to be generated by using this instance.
void	setPageSize(int nSize) set the new page size for the next token to be generated by using this instance.
String	stepNext()
String	stepNext(int nMaxResults)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_OFFSET

public static final int DEFAULT_OFFSET

See Also:

Constant Field Values

DEFAULT_PAGESIZE

public static int DEFAULT_PAGESIZE

PROP_OFFSET

public static final String PROP_OFFSET

See Also:

Constant Field Values

PROP_PAGESIZE

public static final String PROP_PAGESIZE

See Also:

Constant Field Values

SEPARATOR

public static final String SEPARATOR

See Also:

Constant Field Values

NO_NEXT_TOKEN

public static final String NO_NEXT_TOKEN

See Also:

Constant Field Values

Constructor Detail

NextToken

public NextToken()

NextToken

public NextToken(String sToken)
          throws Exception

Throws:

Exception

Method Detail

parse

public void parse(String sToken)
           throws Exception

parse the given token and fill this instance.

Parameters:

sToken - [IN] the last token to be parsed here. Can be empty or null.

Throws:

Exception

stepNext

public String stepNext(int nMaxResults)
                throws Exception

Throws:

Exception

stepNext

public String stepNext()
                throws Exception

Throws:

Exception

finish

public String finish()
              throws Exception

Throws:

Exception

asString

public String asString()
                throws Exception

Throws:

Exception

getOffset

public int getOffset()
              throws Exception

Returns:

the offset from the last parsed token. Has to return 0 as default if last token was empty.

Throws:

Exception

setOffset

public void setOffset(int nOffset)
               throws Exception

set the new offset for the next token to be generated by using this instance.

Parameters:

nOffset - [IN] the new offset. Has to be >= 0.

Throws:

Exception

getPageSize

public int getPageSize()
                throws Exception

Returns:

the page size from the last parsed token. Has to return a default $gt; 0 if last token was empty.

Throws:

Exception

setPageSize

public void setPageSize(int nSize)
                 throws Exception

set the new page size for the next token to be generated by using this instance.

Parameters:

nSize - [IN] the new page size. Has to be $gt;= 1.

Throws:

Exception