Package org.alfresco.ibatis

Class RollupResultHandler

java.lang.Object

org.alfresco.ibatis.RollupResultHandler

All Implemented Interfaces:

org.apache.ibatis.session.ResultHandler

public class RollupResultHandler
extends Object
implements org.apache.ibatis.session.ResultHandler

A ResultHandler that collapses multiple rows based on a set of properties.

This class is derived from earlier RollupRowHandler used to workaround the groupBy and nested ResultMap behaviour in iBatis (2.3.4.726) IBATIS-503.

The set of properties given act as a unique key. When the unique key changes, the collection values from the nested ResultMap are coalesced and the given ResultHandler is called. It is possible to embed several instances of this handler for deeply-nested ResultMap declarations.

Use this instance as a regular ResultHandler, but with one big exception: call processLastResults() after executing the SQL statement. Remove the groupBy attribute from the iBatis ResultMap declaration.

Example iBatis 2.x (TODO migrate example to MyBatis 3.x):

    <resultMap id="result_AuditQueryAllValues"
               extends="alfresco.audit.result_AuditQueryNoValues"
               class="AuditQueryResult">
        <result property="auditValues" resultMap="alfresco.propval.result_PropertyIdSearchRow"/>
    </resultMap>
 
 

Example usage:

        RowHandler rowHandler = new RowHandler()
        {
            public void handleRow(Object valueObject)
            {
                // DO SOMETHING
            }
        };
        RollupRowHandler rollupRowHandler = new RollupRowHandler(
                new String[] {"auditEntryId"},
                "auditValues",
                rowHandler,
                maxResults);
        
        if (maxResults > 0)
        {
            // Calculate the maximum results required
            int sqlMaxResults = (maxResults > 0 ? ((maxResults+1) * 20) : Integer.MAX_VALUE);
            
            List rows = template.queryForList(SELECT_ENTRIES_WITH_VALUES, params, 0, sqlMaxResults);
            for (AuditQueryResult row : rows)
            {
                rollupRowHandler.handleRow(row);
            }
            // Don't process last result:
            //    rollupRowHandler.processLastResults();
            //    The last result may be incomplete
        }
        else
        {
            template.queryWithRowHandler(SELECT_ENTRIES_WITH_VALUES, params, rollupRowHandler);
            rollupRowHandler.processLastResults();
        }
 

This class is not thread-safe; use a new instance for each use.

Since:

4.0

Author:

Derek Hulley, janv

Constructor Summary

Constructors

Constructor	Description
RollupResultHandler(org.apache.ibatis.session.Configuration configuration, String[] keyProperties, String collectionProperty, org.apache.ibatis.session.ResultHandler resultHandler)
RollupResultHandler(org.apache.ibatis.session.Configuration configuration, String[] keyProperties, String collectionProperty, org.apache.ibatis.session.ResultHandler resultHandler, int maxResults)

Method Summary

Modifier and Type	Method	Description
void	handleResult(org.apache.ibatis.session.ResultContext context)
void	processLastResults()	Client code must call this method once the query returns so that the final results can be passed to the inner RowHandler.

Methods inherited from class java.lang.Object

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

Constructor Details

RollupResultHandler

public RollupResultHandler(org.apache.ibatis.session.Configuration configuration,
 String[] keyProperties,
 String collectionProperty,
 org.apache.ibatis.session.ResultHandler resultHandler)

Parameters:

keyProperties - the properties that make up the unique key

collectionProperty - the property mapped using a nested ResultMap

resultHandler - the result handler that will receive the rolled-up results

RollupResultHandler

public RollupResultHandler(org.apache.ibatis.session.Configuration configuration,
 String[] keyProperties,
 String collectionProperty,
 org.apache.ibatis.session.ResultHandler resultHandler,
 int maxResults)

Parameters:

keyProperties - the properties that make up the unique key

collectionProperty - the property mapped using a nested ResultMap

resultHandler - the result handler that will receive the rolled-up results

maxResults - the maximum number of results to retrieve (-1 for no limit). Make sure that the query result limit is large enough to produce this at least this number of results

Method Details

handleResult

public void handleResult(org.apache.ibatis.session.ResultContext context)

Specified by:

handleResult in interface org.apache.ibatis.session.ResultHandler

processLastResults

public void processLastResults()

Client code must call this method once the query returns so that the final results can be passed to the inner RowHandler. If a query is limited by size, then it is possible that the unprocessed results represent an incomplete final object; in this case it would be best to ignore the last results. If the query is complete (i.e. all results are returned) then this method should be called.

If you want X results and each result is made up of N rows (on average), then set the query limit to:
L = X * (N+1)
and don't call this method.