Hector + Cassandra:获取列族列表

Question

我正在尝试获取我正在使用的当前键空间中的所有列族，因为我想消除错误：

InvalidRequestException(why:[column family] already exists in keyspace)

我的逻辑是获取当前键空间中的所有列族&检查返回的列表中是否出现特定的列族。所以，我试着：

KeyspaceDefinition keyspaceDef = HFactory.createKeyspaceDefinition("test");

..。

List<ColumnFamilyDefinition> lsCf = keyspaceDef.getCfDefs();

似乎在创建

List<ColumnFamilyDefinition> lsCf = keyspaceDef.getCfDefs();

我执行了一个System.out.println(keyspaceDef.getCfDefs())，它返回了

[]

一个空的列表--这是我所期望的。我不明白的是为什么List<ColumnFamilyDefinition> lsCf = keyspaceDef.getCfDefs();是不正确的。Eclipse不同意这一行的"List“部分。除此之外，看起来他的代码是正确的。有没有人能告诉我为什么这条线是错的，或者我的方法是不是错了？

下面是完整的代码片段：

package org.cassandra.examples;

import me.prettyprint.cassandra.model.BasicColumnFamilyDefinition;
import me.prettyprint.cassandra.service.CassandraHostConfigurator;
import me.prettyprint.cassandra.service.ThriftCfDef;
import me.prettyprint.cassandra.service.ThriftCluster;
import me.prettyprint.hector.api.Cluster;
import me.prettyprint.hector.api.Keyspace;
import me.prettyprint.hector.api.exceptions.HectorException;
import me.prettyprint.hector.api.factory.HFactory;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;

import me.prettyprint.cassandra.serializers.StringSerializer;
import me.prettyprint.cassandra.service.*;
import me.prettyprint.cassandra.model.BasicColumnDefinition;
import me.prettyprint.cassandra.model.BasicColumnFamilyDefinition;
import me.prettyprint.cassandra.model.thrift.ThriftConverter;

import org.apache.cassandra.db.ColumnFamily;
import org.apache.cassandra.thrift.Cassandra;
import me.prettyprint.cassandra.service.ThriftKsDef;
import me.prettyprint.hector.api.*;
import me.prettyprint.hector.api.beans.HColumn;
import me.prettyprint.hector.api.beans.HSuperColumn;
import me.prettyprint.hector.api.ddl.ColumnFamilyDefinition;
import me.prettyprint.hector.api.ddl.ColumnIndexType;
import me.prettyprint.hector.api.ddl.ComparatorType;
import me.prettyprint.hector.api.ddl.KeyspaceDefinition;
import me.prettyprint.hector.api.factory.HFactory;
import me.prettyprint.hector.api.mutation.Mutator;
import me.prettyprint.cassandra.service.template.ColumnFamilyTemplate;
import me.prettyprint.cassandra.service.template.ColumnFamilyUpdater;
import me.prettyprint.cassandra.service.template.ThriftColumnFamilyTemplate;
import me.prettyprint.hector.api.mutation.Mutator;
import me.prettyprint.hector.api.query.ColumnQuery;
import me.prettyprint.hector.api.query.QueryResult;
import me.prettyprint.hector.api.query.SuperColumnQuery;

public class HectorTest {
    private static String keyspaceName = "test3";
    private static KeyspaceDefinition newKeyspaceDef;
    private static Cluster cluster;
    private static Keyspace ksp;

    public static void main(String[] args) {

        cluster = HFactory.getOrCreateCluster("test cluster", "xxx.xxx.x.xx:9160");
        newKeyspaceDef = HFactory.createKeyspaceDefinition(keyspaceName);
        ColumnFamilyDefinition cfDef = HFactory.createColumnFamilyDefinition("MyKeyspace",                              
                "ColumnFamilyName", 
                ComparatorType.BYTESTYPE);
        List<ColumnFamilyDefinition> lCf = newKeyspaceDef.getCfDefs(); //= new ArrayList<ColumnFamilyDefinition>();
        if((cluster.describeKeyspace(keyspaceName)) == null){
            createSchema();
        }

        ksp = HFactory.createKeyspace(keyspaceName, cluster);
        //Articles art = new Articles(cluster, newKeyspaceDef);
        //cluster.dropColumnFamily(keyspaceName, "Articles");


    }

    public static void createSchema(){
        cluster.addKeyspace(newKeyspaceDef,true);
    }
}

错误：

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    List cannot be resolved to a type

    at org.cassandra.examples.HectorTest.main(HectorTest.java:55)

Answer 1

添加

import java.util.List; 

为了你的进口。在eclipse中，CTRL-SHIFT-O将为您组织导入，并添加任何缺少的内容。