休眠搜索-在布尔查询中处理null

Question

Is there a best practice for handling optional sub-queries? So say my search service has

query = builder.bool().must(createQuery(field1, term1)).must(createQuery(field2, term2)).createQuery();

createQuery(field, term) {
     if(term != null) {
          return builder.keyword().onField(field).matching(term).createQuery();
     }
     return null;
}

With the default QueryBuilder if I use a query like this and the term is null, the resulting query is "+term1 +null" or something along those lines, which causes a null pointer exception when the query is executed against the index. Is there a recommended way to avoid this issue? I was thinking about a custom QueryBuilder but I'm not sure how to tell the fulltext session to use my implementation rather than it's default. The only other way I can think of is something like

query;
query1 = createQuery(field1, term1);
query2 = createQuery(field2, term2);

if(query1 != null && query2 != null) {
    query = builder.bool().must(query1).must(query2).createQuery();
} else if(query1 != null && query2 == null) {
    query = query1;
} else if(query1 == null && query2 != null) {
    query = query2;
}

createQuery(field, term) {
     if(term != null) {
          return builder.keyword().onField(field).matching(term).createQuery();
     }
     return null;
}

But this gets really messy really fast if there are more than a handful of sub-queries.

Answer 1

what about this

    org.json.JSONObject json = new org.json.JSONObject();
    json.put(field1, term1);
    json.put(field2, term2);
    ...


    bool = builder.bool();
    for (Iterator keys = json.keys(); keys.hasNext();) {
        String field = (String) keys.next();
        String term = (String) json.get(field);
        q = createQuery(field, term);
        if (q != null) {
            bool.must(q);
        }
    }
    query = bool.createQuery();

if you have duplicate fields with different terms you must use this :

    org.json.JSONObject json = new org.json.JSONObject();
    json.append(field1, term1);
    json.append(field2, term2);
    ...


    bool = builder.bool();
    for (Iterator keys = json.keys(); keys.hasNext();) {
        String field = (String) keys.next();
        JSONArray terms = (JSONArray) json.get(field);
        for (int i = 0; i < terms.length(); i++) {
            String term = (String) terms.get(i);
            q = createQuery(field, term);
            if (q != null) {
                bool.must(q);
            }
        }
    }
    query = bool.createQuery();

Answer 2

What you might do is introducing a method whose sole purpose would be to add a "must" in a null-safe way. Ie do something like this:

BooleanJunction junction = builder.bool();
must(junction, createQuery(field1, term1));
must(junction, createQuery(field2, term2));
query = junction.createQuery();

void must(BooleanJunction junction, Query query) {
    if (query != null) {
        junction.must(query);
    }
}

Query createQuery(String field, Object term) {
     if(term != null) {
          return builder.keyword().onField(field).matching(term).createQuery();
     }
     return null;
}

This would take out the "fluidity" of the BooleanJunction API, but since it's at the top-level only, I guess it's not so bad.