Question

我正在使用Java Hector API从Cassandra数据库中检索数据，如下所示：

public static void retrieveData() {
    try {
        //Create a cluster object from your existing Cassandra cluster
        Cluster cluster = HFactory.getOrCreateCluster("Test Cluster", "localhost:9160");

        //Create a keyspace object from the existing keyspace we created using CLI
        Keyspace keyspace = HFactory.createKeyspace("TestDB", cluster);

        SliceQuery<String, String, String> sliceQuery = HFactory.createSliceQuery(keyspace, stringSerializer, stringSerializer, stringSerializer);
        sliceQuery.setColumnFamily("ClientHeaders").setKey("1234");
        sliceQuery.setRange("", "", false, 10);
        sliceQuery.setColumnNames("ip_address","uuid");
        QueryResult<ColumnSlice<String, String>> result = sliceQuery.execute();                 
        System.out.println("\nInserted data is as follows:\n" + result.get());   
    } catch (Exception ex) {
        System.out.println("Error encountered while retrieving data!!");
        ex.printStackTrace() ;
    }

所以我按照以下顺序查询检索到的值：

ColumnSlice（[HColumn（IP地址= 203.110.85.171）， HColumn（UUID = a3363400-abfd-0130-e2cf-07b5c765964c）]）

但是我想在一些字符串变量（string ip = ip_address等）中提取结果并使用。但我不明白该怎么做？请帮忙。感谢。

Answer 1

基于Hector的JavaDoc（QueryResult，ColumnSlice和HColumn），您应该可以这样做：

ColumnSlice columnSlice = result.get();
HColumn<String, String> column = columnSlice.getColumnByName("ip_address");
System.out.println("The value of ip_address is " + column.getValue());

或者

for (HColumn<String, String> column : result.get().getColumns()) {
    System.out.println("The value of " + column.getName() + " is " + column.getValue());
}

Answer 2

尝试这样做：

 if (result != null && result.get() != null) {
            List<HColumn<String, String>> resultCols = result.get().getColumns();
            for (HColumn<String, String> col : resultCols)
            {
               System.out.println(col.getValue());
            }

从Hector QueryResult对象获取字符串

2 个答案: