Here, is a sample..
package org.zero.index.batch.read;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.batch.item.database.AbstractPagingItemReader;
import org.springframework.data.mongodb.core.MongoOperations;
import org.springframework.util.Assert;
public class MongodbPagingItemReader<T> extends AbstractPagingItemReader<T> {
private MongoOperations mongoOperations;
private QueryContext<T> queryContext;
private boolean strict;
private static final Logger LOG = LoggerFactory
.getLogger(MongodbPagingItemReader.class);
@Override
protected void doReadPage() {
if (results == null) {
results = new CopyOnWriteArrayList<T>();
} else {
results.clear();
}
final List<T> result = mongoOperations.find(
queryContext.getQuery().limit(getPageSize()).skip(getPage()),
queryContext.getEntityClassName(), queryContext.getCollectionName());
if ((getPage() == 0) && result.isEmpty()) {
if (strict) {
throw new IllegalStateException(
"No matching documents found (reader is in 'strict' mode)");
}
LOG.warn("No matching documents found");
return;
}
results.addAll(result);
}
@Override
protected void doJumpToPage(final int itemIndex) {
// do nothing
}
/**
* @param mongoOperations
* the mongoOperations to set
*/
public void setMongoOperations(final MongoOperations mongoOperations) {
this.mongoOperations = mongoOperations;
}
/**
* @param queryContext
* the queryContext to set
*/
public void setQueryContext(final QueryContext<T> queryContext) {
this.queryContext = queryContext;
}
/**
* @param strict
*/
public void setStrict(final boolean strict) {
this.strict = strict;
}
@Override
public void afterPropertiesSet() throws Exception {
super.afterPropertiesSet();
Assert.notNull(mongoOperations, "mongoOperations is null");
Assert.notNull(queryContext, "queryContext is null");
}
}