java如何在spring批处理中使用MongoItemReader的聚合查询

11 月，4 周 Questions & Answers 2701

在setQuery（）中，我必须使用聚合查询而不是基本查询。这可能吗？请建议我怎么做？我的聚合查询已准备就绪，但不确定如何在spring批处理中使用它

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; }

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(); } }

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; }

# 2 楼答案

为了能够在作业中使用聚合，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。下面是该自定义类的一个简单示例：

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);
    }
}

如果你仔细观察，你会发现它是使用Spring框架中的MongoItemReader创建的，你可以在org上看到这个类。springframework。一批项目数据MongoItemReader，有一种方法可以创建一个扩展AbstractPaginatedDaitaItemReader的全新类，如果你看一看“doPageRead”方法，你应该能够看到它只使用MongoTemplate的find操作，因此不可能在其中使用聚合操作

以下是我们的CustomReader如何使用它：

@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;
}

正如您可能注意到的，您还需要一个MongoTemplate实例，下面是它的工作原理：

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

其中，MongoDbFactory是spring framework的一个自动连接对象

希望这足以帮助你

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java如何在spring批处理中使用MongoItemReader的聚合查询

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