Cassandra Database(3)Hector Scala Class

最新推荐文章于 2024-06-19 15:31:29 发布

原创最新推荐文章于 2024-06-19 15:31:29 发布 · 151 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#scala #数据库 #java

Database 专栏收录该内容

53 篇文章

订阅专栏

本文详细介绍了使用最新 Cassandra 分支 1.2 的自我构建过程，包括创建模式、插入和获取案例类对象的方法。通过 Hector Scala 类实现数据操作，包括定义模式、插入数据和执行查询等步骤。同时，展示了如何使用 Hector 进行范围查询、多获取、分页查询和创建索引等高级查询技巧，并提供了将 Java 集合转换为 Scala 集合的方法。最后，讨论了如何解决在 Scala 中使用 BigDecimal 类型时遇到的类型不匹配问题。

Cassandra Database(3)Hector Scala Class

Actually, I am using the latest cassandra from branch 1.2 and I build it myself.

1. Creating the Schema and Insert/Get
The case class object will be as follow
package com.sillyat.easycassandraserver.models

import org.joda.time.DateTime

case class Product(id: Option[Long], productName: String, create: DateTime, productPrice: BigDecimal, productCode: String, country: String)

The sample of the Schema and Insert/Get

package com.sillycat.easycassandraserver.apps

import me.prettyprint.hector.api.{Keyspace, Cluster}
import me.prettyprint.hector.api.factory.HFactory
import me.prettyprint.cassandra.model.BasicColumnFamilyDefinition
import me.prettyprint.hector.api.ddl.{KeyspaceDefinition, ColumnFamilyDefinition, ComparatorType}
import me.prettyprint.cassandra.service.ThriftCfDef
import java.util.Arrays
import me.prettyprint.hector.api.mutation.Mutator
import me.prettyprint.cassandra.serializers.{LongSerializer, StringSerializer, BigDecimalSerializer}
import com.sillyat.easycassandraserver.models.Product
import org.joda.time.DateTime
import me.prettyprint.hector.api.query.{QueryResult, ColumnQuery}
import me.prettyprint.hector.api.beans.HColumn

object CassandraShemaDataDemoApp extends App{
val clusterName = "TestCluster"
val host = "localhost"
val port = 9160

val keyspaceName = "sillycat"
val columnFamilyName = "products"

val cluster: Cluster = HFactory.getOrCreateCluster("TestCluster", host + ":" + 9160)

//drop the schema
cluster.describeKeyspace(keyspaceName) match {
    case null => println("There is no keyspace yet.")
    case _    => cluster.dropKeyspace(keyspaceName)
}

//define the schema
val columnFamilyProducts: BasicColumnFamilyDefinition = new BasicColumnFamilyDefinition()
columnFamilyProducts.setKeyspaceName(keyspaceName)
columnFamilyProducts.setName(columnFamilyName)

columnFamilyProducts.setKeyValidationClass(ComparatorType.UTF8TYPE.getClassName())
columnFamilyProducts.setComparatorType(ComparatorType.UTF8TYPE)

//columnFamilyProducts.setDefaultValidationClass(ComparatorType.UTF8TYPE.getClassName())
//columnFamilyProducts.setDefaultValidationClass(ComparatorType.DECIMALTYPE.getClassName())
//columnFamilyProducts.setDefaultValidationClass(ComparatorType.ASCIITYPE.getClassName())
//columnFamilyProducts.setDefaultValidationClass(ComparatorType.COMPOSITETYPE.getClassName())

val productsFamily: ColumnFamilyDefinition = new ThriftCfDef(columnFamilyProducts);

val keyspaceDefinition: KeyspaceDefinition =
    HFactory.createKeyspaceDefinition(keyspaceName, "org.apache.cassandra.locator.SimpleStrategy",
      1, Arrays.asList(productsFamily))

cluster.addKeyspace(keyspaceDefinition);

//insert data
val keyspaceOperator: Keyspace = HFactory.createKeyspace(keyspaceName, cluster)

val mutator: Mutator[String] = HFactory.createMutator(keyspaceOperator, StringSerializer.get())

val p1 = Product(Some(1), "IPHONE5", DateTime.now, 499.99, "iphone5", "China")
val p2 = Product(Some(2), "IPHONE4", DateTime.now, 199.99, "iphone4", "US")
val p3 = Product(Some(3), "IPHONE4S", DateTime.now, 299.99, "iphone4s", "TW")

//single insert p1
mutator.insert(
    p1.productCode,
    columnFamilyName,
    HFactory.createColumn("ProductName",
      p1.productName,
      StringSerializer.get(),
      StringSerializer.get()
    )
)

mutator.insert(
    p1.productCode,
    columnFamilyName,
    HFactory.createColumn("Country",
      p1.country,
      StringSerializer.get(),
      StringSerializer.get()
    )
)

mutator.insert(
    p1.productCode,
    columnFamilyName,
    HFactory.createColumn("ProductPrice",
      java.math.BigDecimal.valueOf(p1.productPrice.doubleValue()),
      StringSerializer.get(),
      BigDecimalSerializer.get()
    )
)

//get p1
val bigdecimalColumnQuery: ColumnQuery[String, String, java.math.BigDecimal] = HFactory.createColumnQuery(keyspaceOperator,
    StringSerializer.get(),
    StringSerializer.get(),
    BigDecimalSerializer.get())
bigdecimalColumnQuery.setColumnFamily(columnFamilyName).setKey(p1.productCode).setName("ProductPrice")
val result1: QueryResult[HColumn[String, java.math.BigDecimal]] = bigdecimalColumnQuery.execute()

val stringColumnQuery: ColumnQuery[String, String, String] = HFactory.createColumnQuery(keyspaceOperator,
    StringSerializer.get(),
    StringSerializer.get(),
    StringSerializer.get())
stringColumnQuery.setColumnFamily(columnFamilyName).setKey(p1.productCode).setName("ProductName")
val result2: QueryResult[HColumn[String, String]] = stringColumnQuery.execute()

stringColumnQuery.setColumnFamily(columnFamilyName).setKey(p1.productCode).setName("Country")
val result3: QueryResult[HColumn[String, String]] = stringColumnQuery.execute()

println("Read HColumn from cassandra: " + result1.get())
println("Read HColumn from cassandra: " + result2.get())
println("Read HColumn from cassandra: " + result3.get())
println("Verify on CLI with: get products['iphone5']; ")

//multiple insert p2,p3
//p2
mutator.addInsertion(
    p2.productCode,
    columnFamilyName,
    HFactory.createColumn("ProductName",
      p2.productName,
      StringSerializer.get(),
      StringSerializer.get()
    )
)

mutator.addInsertion(
    p2.productCode,
    columnFamilyName,
    HFactory.createColumn("Country",
      p2.country,
      StringSerializer.get(),
      StringSerializer.get()
    )
)

mutator.addInsertion(
    p2.productCode,
    columnFamilyName,
    HFactory.createColumn("ProductPrice",
      java.math.BigDecimal.valueOf(p2.productPrice.doubleValue()),
      StringSerializer.get(),
      BigDecimalSerializer.get()
    )
)

//p3
mutator.addInsertion(
    p3.productCode,
    columnFamilyName,
    HFactory.createColumn("ProductName",
      p3.productName,
      StringSerializer.get(),
      StringSerializer.get()
    )
)

mutator.addInsertion(
    p3.productCode,
    columnFamilyName,
    HFactory.createColumn("Country",
      p3.country,
      StringSerializer.get(),
      StringSerializer.get()
    )
)

mutator.addInsertion(
    p3.productCode,
    columnFamilyName,
    HFactory.createColumn("ProductPrice",
      java.math.BigDecimal.valueOf(p3.productPrice.doubleValue()),
      StringSerializer.get(),
      BigDecimalSerializer.get()
    )
)

mutator.execute()

bigdecimalColumnQuery.setColumnFamily(columnFamilyName).setKey(p2.productCode).setName("ProductPrice")
val result4: QueryResult[HColumn[String, java.math.BigDecimal]] = bigdecimalColumnQuery.execute()

println("Read HColumn from cassandra: " + result4.get())
println("Verify on CLI with: get products['iphone4s']; ")

cluster.getConnectionManager.shutdown()
}

The most important part is to remember hector is coming from Java, so, sometimes we need to use
java.math.BigDecimal instead of BigDecimal in scala world.

2. The Querys
package com.sillycat.easycassandraserver.apps

import me.prettyprint.hector.api.{Keyspace, Cluster}
import me.prettyprint.hector.api.factory.HFactory
import me.prettyprint.hector.api.query.{MultigetSliceQuery, QueryResult, RangeSlicesQuery}
import com.sillyat.easycassandraserver.models.Product
import scala.Product
import org.joda.time.DateTime
import me.prettyprint.hector.api.beans.{Row, Rows, OrderedRows}
import me.prettyprint.cassandra.serializers.{BigDecimalSerializer, StringSerializer}
import scala.collection.JavaConversions._

object CassandraQueryDemoApp extends App{
val clusterName = "TestCluster"
val host = "localhost"
val port = 9160

val keyspaceName = "sillycat"
val columnFamilyName = "products"

val cluster: Cluster = HFactory.getOrCreateCluster("TestCluster", host + ":" + 9160)

val p1 = Product(Some(1), "IPHONE5", DateTime.now, 499.99, "iphone5", "China")
val p2 = Product(Some(2), "IPHONE4", DateTime.now, 199.99, "iphone4", "US")
val p3 = Product(Some(3), "IPHONE4S", DateTime.now, 299.99, "iphone4s", "TW")

val keyspaceOperator: Keyspace = HFactory.createKeyspace(keyspaceName, cluster)

//range query
val bigDecimalRangeSlicesQuery: RangeSlicesQuery[String, String, java.math.BigDecimal] =
    HFactory.createRangeSlicesQuery(keyspaceOperator, StringSerializer.get(), StringSerializer.get(), BigDecimalSerializer.get())
bigDecimalRangeSlicesQuery.setColumnFamily(columnFamilyName)
bigDecimalRangeSlicesQuery.setKeys(p2.productCode, p2.productCode)
bigDecimalRangeSlicesQuery.setColumnNames("ProductPrice")

val result1: QueryResult[OrderedRows[String, String, java.math.BigDecimal]] = bigDecimalRangeSlicesQuery.execute()
val orderedRows1: OrderedRows[String, String, java.math.BigDecimal]= result1.get()

orderedRows1.toList.foreach( row => println("result1: " + row.getColumnSlice))

val stringRangeSlicesQuery: RangeSlicesQuery[String, String, String] =
    HFactory.createRangeSlicesQuery(keyspaceOperator, StringSerializer.get(), StringSerializer.get(), StringSerializer.get())
stringRangeSlicesQuery.setColumnFamily(columnFamilyName)
stringRangeSlicesQuery.setKeys(p2.productCode, p2.productCode)
stringRangeSlicesQuery.setColumnNames("ProductName", "Country")

val result2: QueryResult[OrderedRows[String, String, String]] = stringRangeSlicesQuery.execute()
val orderedRows2: OrderedRows[String, String, String]= result2.get()

orderedRows2.toList.foreach( row => println("result2: " + row.getColumnSlice))

// createIndexedSlicesQuery   time between some date
// indexedSlicesQuery.addEqualsExpression("birthdate", 1975L);
// indexedSlicesQuery.addGtExpression("birthmonth", 6L);
// indexedSlicesQuery.addLtExpression("birthmonth", 8L);
// indexedSlicesQuery.setColumnNames("birthdate","birthmonth");
// indexedSlicesQuery.setColumnFamily("Indexed1");
// indexedSlicesQuery.setStartKey("");

//multiget
val multigetSliceQuery: MultigetSliceQuery[String, String, String] =
    HFactory.createMultigetSliceQuery(keyspaceOperator, StringSerializer.get(), StringSerializer.get(), StringSerializer.get())
multigetSliceQuery.setColumnFamily(columnFamilyName)
multigetSliceQuery.setKeys(p1.productCode, p2.productCode, p3.productCode)

multigetSliceQuery.setRange(null, null, false, 3) //number 3 is the number of the columns

println(multigetSliceQuery)
val result3: QueryResult[Rows[String, String, String]] = multigetSliceQuery.execute()
val orderedRows3: Rows[String, String, String] = result3.get()

orderedRows3.toList.foreach(row => println("result3: " + row.getColumnSlice))

//pagenation
val pagenationSliceQuery: RangeSlicesQuery[String, String, String] =
    HFactory.createRangeSlicesQuery(keyspaceOperator, StringSerializer.get(), StringSerializer.get(), StringSerializer.get())
pagenationSliceQuery.setColumnFamily(columnFamilyName)
pagenationSliceQuery.setRange("", "", false, 3)
pagenationSliceQuery.setRowCount(3)
val result4: QueryResult[OrderedRows[String, String, String]] = pagenationSliceQuery.execute()
val orderedRows4: OrderedRows[String, String, String] = result4.get()

orderedRows4.toList.foreach(row => println("result4: " + row.getColumnSlice))

val lastRow: Row[String,String,String] = orderedRows4.peekLast()
pagenationSliceQuery.setKeys(lastRow.getKey(), "")
val orderedRows5 = pagenationSliceQuery.execute().get()

orderedRows5.toList.foreach(row => println("result5: " + row.getColumnSlice))
}

How to translate java collections to scala
import scala.collection.JavaConversions._

Tips:
1. Error Message:
type mismatch;
found   : me.prettyprint.cassandra.serializers.BigDecimalSerializer
required: me.prettyprint.hector.api.Serializer[Number]
Note: java.math.BigDecimal <: Number (and me.prettyprint.cassandra.serializers.BigDecimalSerializer <: me.prettyprint.cassandra.serializers.AbstractSerializer[java.math.BigDecimal]), but Java-defined trait Serializer is invariant in type T.
You may wish to investigate a wildcard type such as `_ <: Number`. (SLS 3.2.10)
    p1.productPrice, StringSerializer.get(),BigDecimalSerializer.get()))
^
Solution:
mutator.insert(
    p1.productCode,
    columnFamilyName,
    HFactory.createColumn("ProductPrice",
      java.math.BigDecimal.valueOf(p1.productPrice.doubleValue()),
      StringSerializer.get(),
      BigDecimalSerializer.get()
    )
)

val bigdecimalColumnQuery: ColumnQuery[String, String, java.math.BigDecimal] = HFactory.createColumnQuery(keyspaceOperator,
    StringSerializer.get(),
    StringSerializer.get(),
    BigDecimalSerializer.get())
bigdecimalColumnQuery.setColumnFamily(columnFamilyName).setKey(p1.productCode).setName("ProductPrice")
val result1: QueryResult[HColumn[String, java.math.BigDecimal]] = bigdecimalColumnQuery.execute()

References:
http://fbc.pionier.net.pl/pro/clepsydra/storage/clepsydra-nosql-driver/xref/pl/psnc/synat/a9/nosqldriver/cassandra/CassandraDataMutator.html