Java™ Platform
Standard Ed. 7

Interface SyncResolver

With the information retrieved from the methods getStatus and getConflictValue, the application may make a determination as to which value should be persisted in the data source. The application then calls the SyncResolver method setResolvedValue, which sets the value to be persisted in the RowSet object and also in the data source.

     resolver.setResolvedValue("DEPT", 8390426);
In the preceding line of code, the column name designates the column in the RowSet object that is to be set with the given value. The column number can also be used to designate the column.

An application calls the method setResolvedValue after it has resolved all of the conflicts in the current conflict row and repeats this process for each conflict row in the SyncResolver object.

Navigating a SyncResolver Object

Because a SyncResolver object is a RowSet object, an application can use all of the RowSet methods for moving the cursor to navigate a SyncResolver object. For example, an application can use the RowSet method next to get to each row and then call the SyncResolver method getStatus to see if the row contains a conflict. In a row with one or more conflicts, the application can iterate through the columns to find any non-null values, which will be the values from the data source that are in conflict.

To make it easier to navigate a SyncResolver object, especially when there are large numbers of rows with no conflicts, the SyncResolver interface defines the methods nextConflict and previousConflict, which move only to rows that contain at least one conflict value. Then an application can call the SyncResolver method getConflictValue, supplying it with the column number, to get the conflict value itself. The code fragment in the next section gives an example.

Code Example

The following code fragment demonstrates how a disconnected RowSet object crs might attempt to synchronize itself with the underlying data source and then resolve the conflicts. In the try block, crs calls the method acceptChanges, passing it the Connection object con. If there are no conflicts, the changes in crs are simply written to the data source. However, if there is a conflict, the method acceptChanges throws a SyncProviderException object, and the catch block takes effect. In this example, which illustrates one of the many ways a SyncResolver object can be used, the SyncResolver method nextConflict is used in a while loop. The loop will end when nextConflict returns false, which will occur when there are no more conflict rows in the SyncResolver object resolver. In This particular code fragment, resolver looks for rows that have update conflicts (rows with the status SyncResolver.UPDATE_ROW_CONFLICT), and the rest of this code fragment executes only for rows where conflicts occurred because crs was attempting an update.

After the cursor for resolver has moved to the next conflict row that has an update conflict, the method getRow indicates the number of the current row, and the cursor for the CachedRowSet object crs is moved to the comparable row in crs. By iterating through the columns of that row in both resolver and crs, the conflicting values can be retrieved and compared to decide which one should be persisted. In this code fragment, the value in crs is the one set as the resolved value, which means that it will be used to overwrite the conflict value in the data source.

     try {


     } catch (SyncProviderException spe) {

         SyncResolver resolver = spe.getSyncResolver();

         Object crsValue;  // value in the RowSet object
         Object resolverValue:  // value in the SyncResolver object
         Object resolvedValue:  // value to be persisted

         while(resolver.nextConflict())  {
             if(resolver.getStatus() == SyncResolver.UPDATE_ROW_CONFLICT)  {
                 int row = resolver.getRow();

                 int colCount = crs.getMetaData().getColumnCount();
                 for(int j = 1; j <= colCount; j++) {
                     if (resolver.getConflictValue(j) != null)  {
                         crsValue = crs.getObject(j);
                         resolverValue = resolver.getConflictValue(j);
                         . . .
                         // compare crsValue and resolverValue to determine
                         // which should be the resolved value (the value to persist)
                         resolvedValue = crsValue;

                         resolver.setResolvedValue(j, resolvedValue);
Java™ Platform
Standard Ed. 7

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