深入浅出cassandra 2 第一个可以运行的例子

深入浅出cassandra 2 第一个可以运行的例子

在上一篇文章中，我们成功的建立了一个可以cassandra的实例，同时也让它成功的运行起来，下面的工作就是让我们来简单的操作一下这个号称分布式的号称第二代的数据库系统。

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本文主要关注两个部分，1. 怎么写一个最简单cassandra的sample2. 怎么去分析这个最简单的sample背后隐含的含义

步骤一：
1. 首先我们创建一个工程，然后将cassandra/lib目录下的包，导入到我们的工程中。

2. 非常重要的一点

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编程接口Thrift的配置?使用下面的命令，获取Thrift的压缩包wget -O thrift.tgz?http://gitweb.thrift-rpc.org/?p=thrift.git;a=snapshot;h=HEAD;sf=tgz如果使用Java语言，可以在解压Thrift后，到安装目录下的/lib/java目录，使用ant编译得到libthrift.jar

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注意：编译Java的jar时，需要用到ant，版本需要在1.7.1及以上，不然在编译时提示"not support nested 'typedef' element"的异常

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而且在ant操作时，不能仅仅只拿出lib/java这个文件，须要在整个thrift这个大工程下ant ? ? ??

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步骤二：创建一个类，内容如下：Java代码 ：[c-sharp] view plaincopy

1. package?com.taobao.zhujiadun.basic;??
2. import?org.apache.cassandra.thrift.Cassandra;??
3. import?org.apache.cassandra.thrift.Column;??
4. import?org.apache.cassandra.thrift.ColumnPath;??
5. import?org.apache.cassandra.thrift.ConsistencyLevel;??
6. import?org.apache.cassandra.thrift.InvalidRequestException;??
7. import?org.apache.cassandra.thrift.NotFoundException;??
8. import?org.apache.cassandra.thrift.TimedOutException;??
9. import?org.apache.cassandra.thrift.UnavailableException;??
10. import?org.apache.thrift.TException;??
11. import?org.apache.thrift.protocol.TBinaryProtocol;??
12. import?org.apache.thrift.transport.TSocket;??
13. import?org.apache.thrift.transport.TTransport;??
14. import?org.apache.thrift.transport.TTransportException;??
15. ?public?class?SampleOne?{????
16. ?????static?Cassandra.Client?cassandraClient;????
17. ?????static?TTransport?socket;??
18. ?????
19. ?????
20. ?????private?static?void?init()?throws?TTransportException?{????
21. //?????????String?server?=?"192.168.1.129";????
22. ?????????String?server?=?"localhost";??
23. ?????????int?port?=?9160;????
24. ?????
25. ?????????/*?首先指定cassandra?server的地址?*/????
26. ?????????socket?=?new?TSocket(server,?port);????
27. ?????????System.out.println("?connected?to?"?+?server?+?":"?+?port?+?".");????
28. ?????
29. ?????
30. ?????????/*?指定通信协议为二进制流协议?*/????
31. ?????????TBinaryProtocol?binaryProtocol?=?new?TBinaryProtocol(socket,?false,?false);????
32. ?????????cassandraClient?=?new?Cassandra.Client(binaryProtocol);????
33. ?????
34. ?????
35. ?????????/*?建立通信连接?*/????
36. ?????????socket.open();????
37. ?????}????
38. ?????
39. ?????
40. ?????public?static?void?main(String[]?args)?throws?TException,?TimedOutException,?InvalidRequestException,?UnavailableException,?NotFoundException?{????
41. ?????????/*?初始化连接?*/????
42. ?????????init();????
43. ?????
44. ?????
45. ?????????/*?选择需要操作的Keyspaces，?可以理解成数据库的表?*/????
46. ?????????String?keyspace=?"Keyspace1";????
47. ?????????String?row?=?"employee";????
48. ?????
49. ?????????/*?创建一个Table?Name?*/????
50. ?????????String?tableName?=?"Standard2";??
51. ???????????
52. ?????????/*?插入一条记录?*/??
53. ?????????insertOrUpdate(keyspace,tableName,row,"name","happy?birthday!",System.currentTimeMillis());??
54. ?????????/*?删除一条记录?*/??
55. ?????????//delete(keyspace,tableName,row,"name",System.currentTimeMillis());??
56. ?????????/*?获取一条记录?(由于插入和删除是同一条记录,有可能会检索不到哦!请大家主意!*/??
57. ?????????Column?column?=?getByColumn(keyspace,tableName,row,"name",?System.currentTimeMillis());??
58. ?????????System.out.println("read?row?"?+?row);????
59. ?????????System.out.println("column?name?"?+?":"?+?new?String(column.name));????
60. ?????????System.out.println("column?value"?+?":"?+?new?String(column.value));????
61. ?????????System.out.println("column?timestamp"?+?":"?+?(column.timestamp));????
62. ???????????
63. ?????????close();??
64. ?????}??
65. ???????
66. ?????/**?
67. ??????*?插入记录?
68. ??????*/??
69. ?????public?static?void?insertOrUpdate(String?tableSpace,String?tableName,?String?rowParam,String?ColumnName,String?ColumnValue,long?timeStamp)????
70. ????????throws?TException,?TimedOutException,?InvalidRequestException,?UnavailableException,?NotFoundException{??
71. ?????????/*?选择需要操作的Keyspaces，?存放数据表所在的空间位置?*/????
72. ?????????String?keyspace=?tableSpace;??
73. ?????????/*?数据所在的行标?*/??
74. ?????????String?row?=?rowParam;????
75. ?????
76. ?????????/*?创建一个column?path?*/????
77. ?????????ColumnPath?col?=?new?ColumnPath(tableName);????
78. ?????????col.setColumn(ColumnName.getBytes());???
79. ???????????
80. ?????????/*?执行插入操作，指定keysapce,?row,?col,?和数据内容，?后面两个参数一个是timestamp，?另外一个是consistency_level??
81. ??????????*?timestamp是用来做数据一致性保证的，?而consistency_level是用来控制数据分布的策略，前者的理论依据是bigtable,?后者的理论依据是dynamo??
82. ??????????*/????
83. ????????cassandraClient.insert(keyspace,?row,?col,"i?don't?know".getBytes(),?System.currentTimeMillis(),?ConsistencyLevel.ONE);??
84. ?????}??
85. ???????
86. ?????/**?
87. ??????*?删除记录?
88. ??????*/??
89. ?????public?static?void?delete(String?tableSpace,String?tableName,?String?rowParam,String?ColumnName,long?timeStamp)???
90. ????????throws?TException,?TimedOutException,?InvalidRequestException,?UnavailableException,?NotFoundException{??
91. ?????????/*?选择需要操作的Keyspaces，?存放数据表所在的空间位置?*/????
92. ?????????String?keyspace=?tableSpace;??
93. ?????????/*?数据所在的行标?*/??
94. ?????????String?row?=?rowParam;????
95. ?????
96. ?????????/*?创建一个column?path?*/????
97. ?????????ColumnPath?col?=?new?ColumnPath(tableName);????
98. ?????????col.setColumn(ColumnName.getBytes());???
99. ???????????
100. ?????????/*?执行删除操作，指定keysapce,?row,?col，?后面两个参数一个是timestamp，?另外一个是consistency_level??
101. ??????????*?timestamp是用来做数据一致性保证的，?而consistency_level是用来控制数据分布的策略，前者的理论依据是bigtable,?后者的理论依据是dynamo??
102. ??????????*/????
103. ????????cassandraClient.remove(keyspace,?row,?col,?System.currentTimeMillis(),?ConsistencyLevel.ONE);??
104. ?????}??
105. ???????
106. ?????/**?
107. ??????*?获取数据?
108. ??????*/??
109. ?????public?static?Column?getByColumn(String?tableSpace,String?tableName,?String?rowParam,String?ColumnName,long?timeStamp)???
110. ????throws?TException,?TimedOutException,?InvalidRequestException,?UnavailableException,?NotFoundException{??
111. ??????/*?选择需要操作的Keyspaces，?存放数据表所在的空间位置?*/????
112. ??????String?keyspace=?tableSpace;???
113. ??????/*?数据所在的行标?*/??
114. ??????String?row?=?rowParam;????
115. ??????/*?创建一个column?path?*/????
116. ??????ColumnPath?col?=?new?ColumnPath(tableName);????
117. ??????col.setColumn(ColumnName.getBytes());???
118. ????????
119. ??????/*?执行查询操作，指定keysapce,?row,?col，?timestamp??
120. ???????*?timestamp是用来做数据一致性保证的，?而consistency_level是用来控制数据分布的策略，前者的理论依据是bigtable,?后者的理论依据是dynamo??
121. ???????*/????
122. ??????Column?column?=?cassandraClient.get(keyspace,?row,?col,?ConsistencyLevel.ONE).column;????
123. ??????return?column;??
124. ?????}??
125. ???????
126. ???????
127. ?????/**?
128. ??????*?关闭当前的远程访问连接?
129. ??????*/??
130. ?????public?static?void?close()?{??
131. ?????????socket.close();??
132. ????}??
133. ?}????

为了比较好的理解这些名词解释,我们先看看cassandra的数据模型:?

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Cassandra 的数据模型的基本概念：?
keyspace:?
用于存放 ColumnFamily 的容器，相当于关系数据库中的 Schema 或 database,?
ColumnFamily :?
用于存放 Column 的容器，类似关系数据库中的 table 的概念。?

SuperColumn ：?
它是一个特列殊的 Column, 它的 Value 值可以包函多个 Column?

[c-sharp]

{???//?这是一个SuperColumn??

????name:?"李明杰",??

???//?包含一系列的Columns??

???value:?{??

????street:?{name:?"street",?value:?"1234?x?street",?timestamp:?123456789},??

????city:?{name:?"city",?value:?"san?francisco",?timestamp:?123456789},??

????zip:?{name:?"zip",?value:?"94107",?timestamp:?123456789},??

???}??

}??Columns：?
Cassandra 的最基本单位。由 name , value , timestamp 组成?[c-sharp]

{??//?这是一个column??

??name:?"李明杰",??

??value:?"mydream.limj@gmali.com",??

??timestamp:?123456789??

}???cassandra的数据模型主要就是由上述几种模型构建而成的,很简单吧,的确是这样,最大的好处就是读写数据的API非常简单.?1. 首先我们来说说keyspace是个什么玩意打开storage-conf.xml，找到<Keyspaces>这个xml节点，我们可以看到一段对keyspace的说明， 如下：ColumnFamily在cassandra中概念最接近关系型数据库中的表。而keyspace则是一堆ColumnFamily的集合。如果说ColumnFamily是表，那么我们可以将keyspace称之库

我们来看一段简单的配置。

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Java代码?[c-sharp]

<Keyspaces>??

????<Keyspace?Name="Keyspace1">??

??????<ColumnFamily?CompareWith="BytesType"?Name="Standard1"/>??

??????<ColumnFamily?CompareWith="UTF8Type"?Name="Standard2"/>??

??????<ColumnFamily?CompareWith="TimeUUIDType"?Name="StandardByUUID1"/>??

??????<ColumnFamily?ColumnType="Super"??

????????????????????CompareWith="UTF8Type"??

????????????????????CompareSubcolumnsWith="UTF8Type"??

????????????????????Name="Super1"??

????????????????????Comment="A?column?family?with?supercolumns,?whose?column?and?subcolumn?names?are?UTF8?strings"/>??

????</Keyspace>??

????<Keyspace?Name="ahuaxuan">??

??????<ColumnFamily?CompareWith="BytesType"?Name="test1"/>??

??????<ColumnFamily?CompareWith="UTF8Type"?Name="test2"/>??

??????<ColumnFamily?ColumnType="Super"??

????????????????????CompareWith="UTF8Type"??

????????????????????CompareSubcolumnsWith="UTF8Type"??

????????????????????Name="Super1"??

????????????????????Comment="A?column?family?with?supercolumns,?whose?column?and?subcolumn?names?are?UTF8?strings"/>??

????</Keyspace>??

??</Keyspaces>???

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这段配置表示我们的cassandra中有多个keyspace, 而每个keyspace下又有多个ColumnFamil