我这样做是为了连接cassandra.But我的代码返回错误..这是我的代码
public class CassandraConnection {
public static void main(String[] args) {
String serverIp = "166.78.10.41";
String keyspace = "gamma";
CassandraConnection connection;
Cluster cluster = Cluster.builder()
.addContactPoints(serverIp)
.build();
Session session = cluster.connect(keyspace);
String cqlStatement = "SELECT * FROM TestCF";
for (Row row : session.execute(cqlStatement)) {
System.out.println(row.toString());
}
}
}
这是错误日志..
无法在项目CassandraConnection上执行目标:无法解析项目com.mycompany的依赖项:CassandraConnection:jar:1.0-SNAPSHOT:无法解析以下工件:org.specs2:scalaz-effect_2.11.0-SNAPSHOT:jar :7.0.1-SNAPSHOT,org.scalaz:scalaz-effect_2.9.3:jar:7.1.0-SNAPSHOT:找不到工件org.specs2:scalaz-effect_2.11.0-SNAPSHOT:jar:7.0.1-SNAPSHOT - &gt ; [帮助1]
要查看错误的完整堆栈跟踪,请使用-e开关重新运行Maven。 使用-X开关重新运行Maven以启用完整的调试日志记录。
有关错误和可能的解决方案的更多信息,请阅读以下文章:[帮助1] http://cwiki.apache.org/confluence/display/MAVEN/DependencyResolutionException
答案 0 :(得分:129)
您对此事做过任何研究吗?
您需要一种与cassandra通信的方式,最好的选择是使用高级API。你有很多选择,但是当我们从高层看时,有两种选择。
从datastax的github repo下载并构建驱动程序 OR 使用maven并添加以下依赖项:
<dependency>
<groupId>com.datastax.cassandra</groupId>
<artifactId>cassandra-driver-core</artifactId>
<version>2.1.3</version>
</dependency>
<dependency>
<groupId>com.datastax.cassandra</groupId>
<artifactId>cassandra-driver-mapping</artifactId>
<version>2.1.2</version>
</dependency>
挑选maven是一个好主意,因为它将为你管理所有依赖项,但如果你不使用maven,至少你将学习如何管理jar和读取堆栈跟踪。
driver's documentation很顺利。如果您遇到困难,请阅读该文档,其中包含大量示例。
我将在整个示例中使用以下两个变量。
String serverIP = "127.0.0.1";
String keyspace = "system";
Cluster cluster = Cluster.builder()
.addContactPoints(serverIP)
.build();
Session session = cluster.connect(keyspace);
// you are now connected to the cluster, congrats!
<强>读取强>
String cqlStatement = "SELECT * FROM local";
for (Row row : session.execute(cqlStatement)) {
System.out.println(row.toString());
}
创建/更新/删除强>
// for all three it works the same way (as a note the 'system' keyspace cant
// be modified by users so below im using a keyspace name 'exampkeyspace' and
// a table (or columnfamily) called users
String cqlStatementC = "INSERT INTO exampkeyspace.users (username, password) " +
"VALUES ('Serenity', 'fa3dfQefx')";
String cqlStatementU = "UPDATE exampkeyspace.users " +
"SET password = 'zzaEcvAf32hla'," +
"WHERE username = 'Serenity';";
String cqlStatementD = "DELETE FROM exampkeyspace.users " +
"WHERE username = 'Serenity';";
session.execute(cqlStatementC); // interchangeable, put any of the statements u wish.
创建Keyspace
String cqlStatement = "CREATE KEYSPACE exampkeyspace WITH " +
"replication = {'class':'SimpleStrategy','replication_factor':1}";
session.execute(cqlStatement);
创建ColumnFamily(又名表)
// based on the above keyspace, we would change the cluster and session as follows:
Cluster cluster = Cluster.builder()
.addContactPoints(serverIP)
.build();
Session session = cluster.connect("exampkeyspace");
String cqlStatement = "CREATE TABLE users (" +
" username varchar PRIMARY KEY," +
" password varchar " +
");";
session.execute(cqlStatement);
答案 1 :(得分:0)
要通过Java程序与cassandra连接,您需要向该程序添加一些基本依赖项。将以下依赖项添加到程序中。 Maven依赖项列表:
<dependency>
<groupId>com.datastax.cassandra</groupId>
<artifactId>cassandra-driver-core</artifactId>
<version>3.6.0</version>
</dependency>
<dependency>
<groupId>com.datastax.cassandra</groupId>
<artifactId>cassandra-driver-mapping</artifactId>
<version>3.6.0</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.25</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>21.0</version>
</dependency>
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.20.Final</version>
</dependency>
<dependency>
<groupId>com.codahale.metrics</groupId>
<artifactId>metrics-core</artifactId>
<version>3.0.2</version>
</dependency>
简单的Java程序,用于将cassandra连接到键空间并检索表的值
import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;
public class Test {
public static void main(String[] args) {
String serverIp = "127.0.0.1";
String keyspace = "test";
Cluster cluster = Cluster.builder()
.addContactPoints(serverIp)
.build();
Session session = cluster.connect(keyspace);
String cqlStatement = "SELECT * FROM emp";
for (Row row : session.execute(cqlStatement)) {
System.out.println(row.toString());
}
session.close();
}
}
该程序的Git Hub Repo作为maven项目:GitURL