Question

需求如何变更，我必须在setQuery（）中使用基本查询的聚合查询。这甚至可能吗？请建议我该怎么做？我的聚合查询已准备好但不确定如何在春季批次中使用它

public ItemReader<ProfileCollection> searchMongoItemReader() throws Exception, UnexpectedInputException, ParseException, NonTransientResourceException {

        MongoItemReader<MyCollection> mongoItemReader = new MongoItemReader<>();
        mongoItemReader.setTemplate(myMongoTemplate);
        mongoItemReader.setCollection(myMongoCollection);

        mongoItemReader.setQuery(" Some Simple Query - Basic");

        mongoItemReader.setTargetType(MyCollection.class);
        Map<String, Sort.Direction> sort = new HashMap<>();
        sort.put("field4", Sort.Direction.ASC);
        mongoItemReader.setSort(sort);
        return mongoItemReader;

    }

Answer 1

扩展MongoItemReader并为方法doPageRead（）提供您自己的实现。这样，您将获得全面的分页支持，并且阅读文档将成为步骤的一部分。

public class CustomMongoItemReader<T, O> extends MongoItemReader<T> {
private MongoTemplate template;
private Class<? extends T> inputType;
private Class<O> outputType
private MatchOperation match;
private ProjectionOperation projection;
private String collection;

@Override
protected Iterator<T> doPageRead() {
    Pageable page = PageRequest.of(page, pageSize) //page and page size are coming from the class that MongoItemReader extends
    Aggregation agg = newAggregation(match, projection, skip(page.getPageNumber() * page.getPageSize()), limit(page.getPageSize()));
    return (Iterator<T>) template.aggregate(agg, collection, outputType).iterator();

}
}

其他getter和setters等方法。只需查看MongoItemReader here的源代码即可。我还从中删除了对查询的支持。您也可以使用相同的方法，只需从MongoItemReader复制粘贴即可。与排序相同。

在有读者的课程中，您将执行以下操作：

public MongoItemReader<T> reader() {
    CustomMongoItemReader reader = new CustomMongoItemReader();
    reader.setTemplate(mongoTemplate);
    reader.setName("abc");
    reader.setTargetType(input.class);
    reader.setOutputType(output.class);
    reader.setCollection(myMongoCollection);
    reader.setMatch(Aggregation.match(new Criteria()....)));
    reader.setProjection(Aggregation.project("..","..");
    return reader;
}

Answer 2

要能够在工作中使用聚合，并利用spring batch的所有功能，您必须创建一个自定义ItemReader。扩展AbstractPaginatedDateItemReader，我们可以使用可分页操作中的所有元素。这是该自定义类的简单示例：

public class CustomAggreagationPaginatedItemReader<T> extends AbstractPaginatedDataItemReader<T> implements InitializingBean {

    private static final Pattern PLACEHOLDER = Pattern.compile("\\?(\\d+)");
    private MongoOperations template;
    private Class<? extends T> type;
    private Sort sort;
    private String collection;

    public CustomAggreagationPaginatedItemReader() {
        super();
        setName(ClassUtils.getShortName(CustomAggreagationPaginatedItemReader.class));
    }

    public void setTemplate(MongoOperations template) {
        this.template = template;
    }

    public void setTargetType(Class<? extends T> type) {
        this.type = type;
    }

    public void setSort(Map<String, Sort.Direction> sorts) {
        this.sort = convertToSort(sorts);
    }

    public void setCollection(String collection) {
        this.collection = collection;
    }

    @Override
    @SuppressWarnings("unchecked")
    protected Iterator<T> doPageRead() {
        Pageable pageRequest = new PageRequest(page, pageSize, sort);

        BasicDBObject cursor = new BasicDBObject();
        cursor.append("batchSize", 100);

        SkipOperation skipOperation = skip(Long.valueOf(pageRequest.getPageNumber()) * Long.valueOf(pageRequest.getPageSize()));

        Aggregation aggregation = newAggregation(
                //Include here all your aggreationOperations,
                skipOperation,
                limit(pageRequest.getPageSize())
            ).withOptions(newAggregationOptions().cursor(cursor).build());

        return (Iterator<T>) template.aggregate(aggregation, collection, type).iterator();
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        Assert.state(template != null, "An implementation of MongoOperations is required.");
        Assert.state(type != null, "A type to convert the input into is required.");
        Assert.state(collection != null, "A collection is required.");
    }

    private String replacePlaceholders(String input, List<Object> values) {
        Matcher matcher = PLACEHOLDER.matcher(input);
        String result = input;

        while (matcher.find()) {
            String group = matcher.group();
            int index = Integer.parseInt(matcher.group(1));
            result = result.replace(group, getParameterWithIndex(values, index));
        }

        return result;
    }

    private String getParameterWithIndex(List<Object> values, int index) {
        return JSON.serialize(values.get(index));
    }

    private Sort convertToSort(Map<String, Sort.Direction> sorts) {
        List<Sort.Order> sortValues = new ArrayList<Sort.Order>();

        for (Map.Entry<String, Sort.Direction> curSort : sorts.entrySet()) {
            sortValues.add(new Sort.Order(curSort.getValue(), curSort.getKey()));
        }

        return new Sort(sortValues);
    }
}

如果您仔细观察，可以看到它是使用Spring框架的MongoItemReader创建的，可以在org.springframework.batch.item.data.MongoItemReader上看到该类，这是创建扩展新类的方法AbstractPaginatedDataItemReader，如果您查看“ doPageRead”方法，应该可以看到它仅使用MongoTemplate的find操作，因此无法在其中使用Aggregate操作。

这是我们想要如何使用它的CustomReader的方法：

@Bean
public ItemReader<YourDataClass> reader(MongoTemplate mongoTemplate) {
    CustomAggreagationPaginatedItemReader<YourDataClass> customAggreagationPaginatedItemReader = new CustomAggreagationPaginatedItemReader<>();

    Map<String, Direction> sort = new HashMap<String, Direction>();
    sort.put("id", Direction.ASC);

    customAggreagationPaginatedItemReader.setTemplate(mongoTemplate);
    customAggreagationPaginatedItemReader.setCollection("collectionName");
    customAggreagationPaginatedItemReader.setTargetType(YourDataClass.class);
    customAggreagationPaginatedItemReader.setSort(sort);

    return customAggreagationPaginatedItemReader;
}

您可能会注意到，您还需要一个MongoTemplate实例，这也是它的样子：

@Bean
public MongoTemplate mongoTemplate(MongoDbFactory mongoDbFactory) {
    return new MongoTemplate(mongoDbFactory);
}

其中MongoDbFactory是spring框架自动连接的对象。

希望足以为您提供帮助。

如何在Spring批处理中使用MongoItemReader进行聚合查询

2 个答案: