Question

Hazelcast-我有一个Java.Map和String字段需要查询。我正在尝试使用ValueExtractor来获取Map的值和Strings。有人有一些有关如何执行此操作的示例吗？

编辑：也许是一个类似的问题，但我需要一些示例：hazelcast - is there a way to iterate over a map keys and/or values to query

    public class Client{
       Company company;
       Map<String, String> programs = new HashMap<String, String>();
       String name;

       //some other code here
    }

    // in my search class
    public List<Client> search(Map<DirProperty, String> criteria) {
        ArrayList<Client> users = new ArrayList<Client>();

        if (cachedClients != null) {
        try {
            SqlPredicate predicate = getCachePredicate(criteria);
            log.debug(String.format("Searching forms in cache: %s", criteria.toString()));
            Collection<Client> clientCollection = cachedClients.values(predicate);

            clients = new ArrayList<Client>(clientCollection);

        } catch (Exception e) {
            log.error("Search failed: " + criteria.toString(), e);
        }   
    }
    return users;
}

private SqlPredicate getCachePredicate(Map<DirProperty, String> criteria) throws ParseException {
    String sql = getSqlString(criteria);
    log.debug("Using SQL to search cache: " + sql);
    return new SqlPredicate(sql);
}

private String getSqlString(Map<DirProperty, String> criteria) throws ParseException {
    StringBuilder result = new StringBuilder();

    if (criteria != null && !criteria.isEmpty()) {
        boolean appendAnd = false;
        for (Map.Entry<DirProperty, String> entry : criteria.entrySet()) {
            String key = entry.getKey().getCacheId();
            String value = entry.getValue();

            value = value.replace("'", "''"); // Escape apostrophe

            if (appendAnd) {
                result.append(" AND ");
            }
            // Look for delimiter. Multiple values will be "or"ed together
            if (value.contains("|")) {
                StringTokenizer st = new StringTokenizer(value, "|");
                if (st.countTokens() > 0) {
                    result.append("(");
                    boolean appendOr = false;
                    while (st.hasMoreTokens()) {
                        if (appendOr) {
                            result.append(" OR ");
                        }
                        result.append(getExpression(key, st.nextToken().trim()));
                        appendOr = true;
                    }
                    result.append(")");
                }
            } else if (value.startsWith("!")) {
                value = value.substring(1);
                result.append(getExpression(key, value).replace("=", "!="));

            } else {
                result.append(getExpression(key, value));
            }
            appendAnd = true;
        }
    }

    return result.toString();
}

private String getExpression(String key, String value) throws ParseException {

    String result = null;
    if(key.equals("program")) {
        String op = ">=";
        key = "documentUploadRecords[any].sequenceNumber";
        result = key + " " + op + " '" + value + "'";
     // other if statements here 
     else {
        result = key + " = '" + value + "'";
    }
    return result;
}

运行查询时，这是我收到的错误消息：

java.lang.ClassCastException: java.util.HashMap cannot be cast to java.lang.Comparable
at com.hazelcast.query.impl.predicates.AbstractPredicate.apply(AbstractPredicate.java:62)
at com.hazelcast.map.impl.query.MapQueryEngineImpl.queryTheLocalPartition(MapQueryEngineImpl.java:285)
at com.hazelcast.map.impl.query.MapQueryEngineImpl.querySequential(MapQueryEngineImpl.java:187)
at com.hazelcast.map.impl.query.MapQueryEngineImpl.queryUsingFullTableScan(MapQueryEngineImpl.java:176)
at com.hazelcast.map.impl.query.MapQueryEngineImpl.queryLocalPartitions(MapQueryEngineImpl.java:131)
at com.hazelcast.map.impl.query.QueryOperation.run(QueryOperation.java:51)

Answer 1

Hazelcast代码示例已经有该用例的示例。查看此演示：https://github.com/hazelcast/hazelcast-code-samples/blob/master/distributed-map/custom-attributes/src/main/java/com/test/car/attribute/CarAttributeDemo.java

汽车类包含地图和示例，使用提取器查询这些属性。

用于Java映射和字符串查询的Hazelcast ValueExtractor

1 个答案: