Utility X, Sorter Processing

Another feature in zero system is that it provide the object io.horizon.uca.qr.Sorter to store sorting message in querying or searching operations. This class contains following useful apis:

• <T> JsonObject toJson(Function<Boolean,T> function)
• Sorter add(String field, Boolean asc)
• Sorter clear()

1. Introduction

For example, in some situations you’ll write the code logical in SQL such as:

SELECT S_NAME, S_CODE FROM SEC_USER WHERE I_AGE > 33 ORDER BY S_NAME DESC, S_EMAIL ASC

Here the segment from S_NAME means the sorting operations. Sorting operations contain two elements that you should know:

• mode: ASC/DESC, the sorting mode that for each field.
• priority: In the segment the priority of sorting fields should be in sequence, above SQL statement, S_NAME has high priority.

Zero system utility provide normalized method to process sorter as folllowing:

• static Sorter toSorter(String field, boolean asc)
• static Sorter toSorter(String field, int mode)

There are some flags that you should know, for boolean parameter asc, it’s very clear that no comments also make you understand this api, but for the int parameter mode, you should know:

• ASC mode: asc = true or mode > 0 ( exclude 0 )
• DESC mode: asc = false or mode <= 0 ( include 0 )

2. Source Code

This chapter codes also came from real projects.

    @Address(Addr.TOPICS_SUBSCRIBE)
    public void subscribe(final Message<Envelop> message) {
        final JsonObject pager = Ux.getBody(message);
        final JsonObject filter = new JsonObject().put("userId", Extractor.getUserId(message));
        this.subscribe.query(TargetType.TOPIC, filter, MongoReadOpts.toFull(
                Ux.toPager(pager), 
                Ux.toSorter("subscribeTime", false) // Here order by subscribeTime DESC mode.
        )).setHandler(Ux.toHandler(message));
    }

3. Summary

From above demo you’ll see MongoReadOpts class appeared, it’s mongo db only, we’ll introduce the Mongo usage in zero system in forward tutorials. Here you should know that following code impact the sorting operations:

Ux.toSorter("subscribeTime", false)