MongoItemReaderBuilder shouldn't be throwing an error related to the limit in query when pageSize is provided

[kexsteve]

spring-batch/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/data/builder/MongoItemReaderBuilder.java

Line 290 in 8e8f9c8

Assert.state(this.query.getLimit() != 0, "PageSize in Query object was ignored.");

For example:

new MongoItemReaderBuilder<Document>()
            .collection("test")
            .template(mongoTemplate)
            .targetType(Document.class)
            .query(Query.query(Criteria.where("active").is(false))
            .sorts(ImmutableMap.of("_id", Sort.Direction.ASC))
            .pageSize(100)
            .build();

The line throw an error in MongoItemReaderBuilder:
Assert.state(this.query.getLimit() != 0, "PageSize in Query object was ignored.")

This has been just a warning in MongoItemReader:
log.warn("PageSize in Query object was ignored. Please set it by MongoItemReader.setPageSize().");

[fmbenhassine]

I do confirm, this is indeed inconsistent with the MongoItemReader. However, the issue is in the reader, before being in the builder. When I set a query limit without a page size, I have the warning:

@Test
public void testMongoItemReaderWithQueryLimit() throws Exception {
	MongoItemReader<String> mongoItemReader = new MongoItemReader<>();
	mongoItemReader.setName("mongoReader");
	mongoItemReader.setCollection("test");
	mongoItemReader.setTemplate(template);
	mongoItemReader.setTargetType(String.class);
	mongoItemReader.setQuery(Query.query(Criteria.where("active").is(false)).limit(1000));
	mongoItemReader.setSort(new HashMap<String, Sort.Direction>() {{ put("_id", Sort.Direction.ASC); }});
	mongoItemReader.afterPropertiesSet();

	Assertions.assertNotNull(mongoItemReader);
}

This test passes, and I see the following warning:

[main] WARN org.springframework.batch.item.data.MongoItemReader - PageSize in Query object was ignored. Please set it by MongoItemReader.setPageSize()

However, even if I set the page size as mentioned in the warning, I still see the same warning..

@Test
public void testMongoItemReaderWithQueryLimit() throws Exception {
	MongoItemReader<String> mongoItemReader = new MongoItemReader<>();
	mongoItemReader.setName("mongoReader");
	mongoItemReader.setCollection("test");
	mongoItemReader.setTemplate(template);
	mongoItemReader.setTargetType(String.class);
	mongoItemReader.setQuery(Query.query(Criteria.where("active").is(false)).limit(1000));
	mongoItemReader.setSort(new HashMap<String, Sort.Direction>() {{ put("_id", Sort.Direction.ASC); }});
	mongoItemReader.setPageSize(100);
	mongoItemReader.afterPropertiesSet();

	Assertions.assertNotNull(mongoItemReader);
}

This is because the condition on the query here is incorrect as it does not involve the page size. (and btw, the message PageSize in Query object was ignored is incorrect as well, there is no PageSize parameter in the Query type).

In hindsight, this warning is not needed IMO, because the page size defaults to 10, and could be set by the user to a non-zero value. So in the end, regardless of the query limit, the page size is set. I think we need to fix the reader first, otherwise we would make the builder consistent with an incorrect reader.

[parikshitdutta]

Hi @benas can you please take a look at my PR #3691 for resolving this issue? or please assign it to the respective group to review.

Thank you.

[fmbenhassine]

@parikshitdutta Thank you for the PR! I will take a look.

[parikshitdutta]

thanks @benas, pleasure is mine! looking forward to take some more issues across open spring framework issues, while we fight covid!

[parikshitdutta]

Hi @benas, if you envision any change for this PR that can help, please let me know.

Thank you.

[fmbenhassine]

Resolved with 56fbc27 and backported to 4.2.x.