Java 如何在cassandra中创建键空间?
我用一个片段来理解cassandra和语法:Java 如何在cassandra中创建键空间?,java,eclipse,cassandra,apache-spark,Java,Eclipse,Cassandra,Apache Spark,我用一个片段来理解cassandra和语法: import com.datastax.driver.core.Cluster; import com.datastax.driver.core.ResultSet; import com.datastax.driver.core.Row; import com.datastax.driver.core.Session; public class App { public static void main(String[] args) {
import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.ResultSet;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;
public class App {
public static void main(String[] args) {
Cluster cluster;
Session session;
// Connect to the cluster and key space "demo"
cluster = Cluster.builder().addContactPoint("127.0.0.1").build();
session = cluster.connect("demo");
// Insert one record into the users table
session.execute("INSERT INTO users (lastname, age, city, email, firstname) VALUES ('Jones', 35, 'Austin', 'bob@example.com', 'Bob')");
// Use select to get the user we just entered
ResultSet results = session.execute("SELECT * FROM users WHERE lastname='Jones'");
for (Row row : results) {
System.out.format("%s %d\n", row.getString("firstname"), row.getInt("age"));
}
// Update the same user with a new age
session.execute("update users set age = 36 where lastname = 'Jones'");
// Select and show the change
results = session.execute("select * from users where lastname='Jones'");
for (Row row : results) {
System.out.format("%s %d\n", row.getString("firstname"), row.getInt("age"));
}
// Delete the user from the users table
session.execute("DELETE FROM users WHERE lastname = 'Jones'");
// Show that the user is gone
results = session.execute("SELECT * FROM users");
for (Row row : results) {
System.out.format("%s %d %s %s %s\n", row.getString("lastname"), row.getInt("age"), row.getString("city"),
row.getString("email"), row.getString("firstname"));
}
// Clean up the connection by closing it
cluster.close();
}
}
执行时,我会遇到以下错误:
log4j:WARN No appenders could be found for logger (com.datastax.driver.core.SystemProperties).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Exception in thread "main" com.datastax.driver.core.exceptions.InvalidQueryException: Keyspace 'demo' does not exist
at com.datastax.driver.core.exceptions.InvalidQueryException.copy(InvalidQueryException.java:35)
at com.datastax.driver.core.DefaultResultSetFuture.extractCauseFromExecutionException(DefaultResultSetFuture.java:289)
at com.datastax.driver.core.Cluster.connect(Cluster.java:287)
at org.sparkexamples.cassandraExample.main.App.main(App.java:17)
Caused by: com.datastax.driver.core.exceptions.InvalidQueryException: Keyspace 'demo' does not exist
at com.datastax.driver.core.Responses$Error.asException(Responses.java:103)
at com.datastax.driver.core.DefaultResultSetFuture.onSet(DefaultResultSetFuture.java:140)
at com.datastax.driver.core.RequestHandler.setFinalResult(RequestHandler.java:293)
at com.datastax.driver.core.RequestHandler.onSet(RequestHandler.java:455)
at com.datastax.driver.core.Connection$Dispatcher.messageReceived(Connection.java:734)
at org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:70)
at org.jboss.netty.handler.timeout.IdleStateAwareChannelUpstreamHandler.handleUpstream(IdleStateAwareChannelUpstreamHandler.java:36)
at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
at org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:791)
at org.jboss.netty.handler.timeout.IdleStateHandler.messageReceived(IdleStateHandler.java:294)
at org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:70)
at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
at org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:791)
at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:296)
at org.jboss.netty.handler.codec.oneone.OneToOneDecoder.handleUpstream(OneToOneDecoder.java:70)
at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
at org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:791)
at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:296)
at org.jboss.netty.handler.codec.frame.FrameDecoder.unfoldAndFireMessageReceived(FrameDecoder.java:462)
at org.jboss.netty.handler.codec.frame.FrameDecoder.callDecode(FrameDecoder.java:443)
at org.jboss.netty.handler.codec.frame.FrameDecoder.messageReceived(FrameDecoder.java:303)
at org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:70)
at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:559)
at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:268)
at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:255)
at org.jboss.netty.channel.socket.nio.NioWorker.read(NioWorker.java:88)
at org.jboss.netty.channel.socket.nio.AbstractNioWorker.process(AbstractNioWorker.java:108)
at org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:318)
at org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:89)
at org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:178)
at org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
at org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
在addiction中,我使用spark(maven/libs)配置了所有内容,但我不知道如何使用java代码创建键空间
提前感谢。您可以使用CQL语句创建密钥空间。有关详细信息,请参阅本文档
从java代码运行
SELECT
或CREATE
语句之间没有区别 您已经有了一个会话
实例。使用它发出create keyspace命令:
session.execute("CREATE KEYSPACE IF NOT EXISTS test WITH replication = {"
+ " 'class': 'SimpleStrategy', "
+ " 'replication_factor': '3' "
+ "};" );
如果键空间已经存在,
如果不存在,部分将防止语句抛出错误。创建键空间\u creation.cql如下:
-->vim keyspace_creation.cql
create keyspace demo WITH REPLICATION = {'class' : 'SimpleStrategy','replication_factor': 3 };
USE ycsb;
create table usertable (
y_id varchar primary key,
field0 varchar,
field1 varchar,
field2 varchar,
field3 varchar,
field4 varchar,
field5 varchar,
field6 varchar,
field7 varchar,
field8 varchar,
field9 varchar);
-->cd$CASSANDRA_HOME/bin
-->/cqlsh
cqlsh> source '~/$CASSANDRA_HOME/bin/keyspace_creation.cql';
当然只需像您使用select
、delete
或任何其他语句一样运行它。我使用了您的建议,但得到了相同的错误cluster=cluster.builder().addContactPoint(“127.0.0.1”).build();会话=cluster.connect(“测试”);执行(“使用复制创建键空间测试”+”={'class':'SimpleStrategy','replication_factor':3};”
您不应该使用cluster.connect(“test”)
,因为键空间还不存在。使用session=cluster.connect()代码>取而代之。