我用 hector 插入数据并用 JDBC 取回数据。
除了索引列之外,数据没有任何意义,我知道这是因为 cassandra 将数据存储为字节,然后在读取时转换它(客户端转换它)
有谁知道如何在 JDBC for cassandra 中执行此操作?
我的代码:
public static void main(String[] args) throws SQLException
{
Connection con = null;
String _KS = "StringMsg";
String _CFDef = "Tweets";
try
{
Class.forName("org.apache.cassandra.cql.jdbc.CassandraDriver");
con = DriverManager.getConnection("jdbc:cassandra://localhost:9160/" + _KS);
String query = "SELECT username, email, msg, id FROM " + _CFDef + " WHERE 'username'='LTodorov'";
Statement stmt = con.createStatement();
ResultSet result = stmt.executeQuery(query);
System.out.println("hi");
int i=0;
while (result.next())
{
System.out.println(result.getString("id"));
System.out.println(result.getString("username"));
System.out.println(result.getString("msg"));
System.out.println(result.getString("email"));
System.out.print("count:" + i + "\n\n");i++;
}
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}
catch (SQLException e) {
e.printStackTrace();
}
finally
{
if (con != null)
{
try
{
con.close();
}
catch (SQLException e)
{
e.printStackTrace();
}
con = null;
}
}
}
结果:
hi
java.nio.HeapByteBuffer[pos=237 lim=258 cap=798]
LTodorov
java.nio.HeapByteBuffer[pos=184 lim=209 cap=798]
java.nio.HeapByteBuffer[pos=144 lim=155 cap=798]
count:0
命令行结果:
GET Tweets Where username=LTodorov;
-------------------
RowKey: LTodorov1330045080096
=> (column=email, value=6c5f6c74404162762e6267, timestamp=1330045080214000)
=> (column=id, value=4c546f646f726f7631333330303435303830303936, timestamp=13300
45080098000)
=> (column=msg, value=54686973206973206d616b696e67206d652073616466616365, timest
amp=1330045080210000)
=> (column=username, value=LTodorov, timestamp=1330045080217000)
带有“假设推文验证器为 utf8”的 Cli 结果;
RowKey: LTodorov1330045080096
=> (column=email, value=l_ld@Abv.bg, timestamp=1330045080214000)
=> (column=id, value=LTodorov1330045080096, timestamp=1330045080098000)
=> (column=msg, value=This is making me sadface, timestamp=1330045080210000)
=> (column=username, value=LTodorov, timestamp=1330045080217000)
列族定义:
CREATE COLUMN FAMILY Tweets
WITH comparator = UTF8Type
AND key_validation_class=UTF8Type
AND column_metadata = [
{column_name: id, validation_class: UTF8Type}
{column_name: email, validation_class: UTF8Type}
{column_name: msg, validation_class: UTF8Type}
{column_name: user, validation_class: UTF8Type}
任何 cassandra 大师有任何指示吗?我正在取回数据,但它应该在 java 中进行转换,还是应该由 JDBC api 完成工作,还是 cassandra 的事情?(我认为这不能由 cassandra 解决)