cassandra学习笔记

(一)依赖:cassandra.jar

             libthrift.jar

(二)连接:

    //该方法将返回一个Cassandra.Client实例,该实例包含和server端指定节点会话的API

1.  
2.      public Cassandra.Client getClient()
3.     {
4.         //192.168.0.169为想连接到的某个节点的ip,9160为端口
5.  
6.         TSocket socket = new TSocket("192.168.0.169", 9160);
7.  
8.         TTransport transport_ = socket;
9.  
10.         TBinaryProtocol binaryProtocol = new TBinaryProtocol(transport_,false, false);
11.         Cassandra.Client cassandraClient = newCassandra.Client(binaryProtocol);
12.  
13.         try
14.         {
15.             transport_.open();
16.         }
17.         catch( e)
18.         {
19.             // Should move this to Log4J as well probably…
20.             .err.println("Exception " + e.getMessage());          
21.             e.printStackTrace();
22.         }
23.       
24.         return cassandraClient;
25.      
26.     }
27.  

(三)API

1)该方法向key的指定path插入一个数据，另外想要对key某指定path的数据进行修改也使用这个方法

   代码中的cli是一个Cassandra.Client实例

1.  
2.      public void test_insert()
3.     {
4.         try {
5.              tableName = "Table1";
6.              key = "testkey";
7.              columnFamily = "Standard1";
8.              columnName = "testColumn";
9.              value = "testValue";
10.  
11.             //对数据进行定位
12.              path = columnFamily+":"+columnName;
13.             //向cassandra中插入一条数据
14.             cli.insert(tableName,key,path,value.getBytes(),.currentTimeMillis(),true);
15.         } catch (InvalidRequestException e) {
16.             e.printStackTrace();
17.         } catch (TException e) {
18.             e.printStackTrace();
19.         } catch (UnavailableException e) {
20.             e.printStackTrace();
21.         }
22.     }
23.  

2)该方法试用Cql语句的方式发送请求，有一个问题就是当请求的参数或不正确的时候，方法不会报错，只是返回为空；

   但是在语法出现错误的时候还是会有InvalidRequestException抛出,提示Unresolved compilation problems

   代码中的cli是一个Cassandra.Client实例

1.  
2.    public void test_excuteQuery()
3.     {
4.         try {
5.             cli.executeQuery("set Table1.Standard1['testKey2']['testColumn']=’testValue2′");
6.             CqlResult_t crt = cli.executeQuery("get Table1.Standard1['testKey2']");
7.             List> rs = crt.getResultSet();
8.             //遍历显示所有column_t中的内容
9.             if(rs != null){
10.                 for(int i = 0 ; i < rs.size() ; i++){
11.                     Map map = rs.get(i);
12.                     for( key : map.keySet()){
13.                         .out.println(key+" : "+map.get(key));
14.                     }
15.                 }
16.             }else{
17.                 .out.println("result set is null");
18.             }
19.         } catch (TException e) {
20.             e.printStackTrace();
21.         }
22.     }
23.  

3)根据path信息获取一个column

   path是一个定位信息，standard column family是两层 super column family是三层

   superColumnFamily:superColumn:standardColumn。

1.  
2.    public void test_get_column()
3.     {
4.          tableName = "Table1";
5.          key = "testKey2";
6.          columnFamily = "Standard1";
7.          column = "testColumn";
8.          path = columnFamily+":"+column;
9.         try {
10.             column_t cmt = cli.get_column(tableName, key, path);
11.             //以下两个是等价的
12.             .out.println(cmt.getColumnName());
13.             .out.println(cmt.getFieldValue(1));
14.             //以下两个是等价的
15.             .out.println(new (cmt.getValue(),"UTF-8"));
16.             .out.println(new ((byte[])cmt.getFieldValue(2),"UTF-8"));
17.             //以下两个是等价的
18.             .out.println(cmt.getTimestamp());
19.             .out.println(cmt.getFieldValue(3));
20.           
21.         } catch (InvalidRequestException e) {
22.             e.printStackTrace();
23.         } catch (NotFoundException e) {
24.             e.printStackTrace();
25.         } catch (TException e) {
26.             e.printStackTrace();
27.         } catch ( e) {
28.             e.printStackTrace();
29.         }
30.     }

4)

    //术语解释：每个key都对应一个Row的信息这个Row的信息又按照columnFamliy 分成了很多slice

    //给定table,key和columnFamily的信息，
    //此方法将返回，该key在当前columnFamily的slice中有都少个column元素
    //该例子中key:”testKey2″在columnFamily:”Standard1″中的slice有几个column元素

1.  
2.     public void test_get_column_count()
3.     {
4.          tableName = "Table1";
5.          keyName = "testKey2";
6.          columnFamily = "Standard1";
7.         try {
8.             .out.println(cli.get_column_count(tableName, keyName, columnFamily));
9.         } catch (InvalidRequestException e) {
10.             e.printStackTrace();
11.         } catch (TException e) {
12.             e.printStackTrace();
13.         }
14.     }
15.  

5) //暂不确定

    //根据给定的时间点，取出以后的对应给定key的一组columns
    //但是好像在时间上有延迟,这个不确定

1.  
2.     public void test_get_columns_since()
3.     {
4.          tableName = "Table1";
5.          keyName = "testKey2";
6.          columnFamily = "Standard1";
7.          sinceTime = .currentTimeMillis()-5000*1000;//取当前时间之前120秒以内的
8.         try {
9.             List cmts = cli.get_columns_since(tableName , keyName , columnFamily , sinceTime);
10.             .out.println("cmts size : "+cmts.size());
11.         } catch (InvalidRequestException e) {
12.             e.printStackTrace();
13.         } catch (NotFoundException e) {
14.             e.printStackTrace();
15.         } catch (TException e) {
16.             e.printStackTrace();
17.         } catch ( e) {
18.             e.printStackTrace();
19.         }
20.     }
21.