使用Java实现IBM Cloudant聚合查询
要使用Java实现IBM Cloudant的聚合查询，首先需要添加以下依赖的Maven坐标：
<dependency>
<groupId>com.ibm.cloud</groupId>
<artifactId>cloudant</artifactId>
<version>10.10.1</version>
</dependency>
然后，可以使用以下示例Java代码来实现各种数据聚合查询：
1. 统计文档总数:
import com.cloudant.client.api.ClientBuilder;
import com.cloudant.client.api.CloudantClient;
public class AggregateQueriesExample {
public static void main(String[] args) {
CloudantClient client = ClientBuilder.account("USERNAME")
.username("USERNAME")
.password("PASSWORD")
.build();
long totalDocuments = client.database("DATABASE_NAME").info().getDocCount();
System.out.println("Total Documents: " + totalDocuments);
}
}
2. 求和聚合查询:
import com.cloudant.client.api.ClientBuilder;
import com.cloudant.client.api.CloudantClient;
import com.cloudant.client.api.Database;
import com.cloudant.client.api.model.FindByIndexOptions;
import com.cloudant.client.org.lightcouch.NoDocumentException;
import com.cloudant.client.org.lightcouch.View;
public class AggregateQueriesExample {
public static void main(String[] args) {
CloudantClient client = ClientBuilder.account("USERNAME")
.username("USERNAME")
.password("PASSWORD")
.build();
Database database = client.database("DATABASE_NAME", false);
View view = database.getViewRequestBuilder("DESIGN_DOC_NAME", "VIEW_NAME")
.newFindByIndexOptions()
.reduce(true)
.build();
try {
double sum = (Double) view.getResponse().getRows().get(0).getValue();
System.out.println("Sum: " + sum);
} catch (NoDocumentException e) {
System.out.println("No documents found for the view.");
}
}
}
3. 平均值聚合查询:
import com.cloudant.client.api.ClientBuilder;
import com.cloudant.client.api.CloudantClient;
import com.cloudant.client.api.Database;
import com.cloudant.client.api.model.FindByIndexOptions;
import com.cloudant.client.org.lightcouch.NoDocumentException;
import com.cloudant.client.org.lightcouch.View;
public class AggregateQueriesExample {
public static void main(String[] args) {
CloudantClient client = ClientBuilder.account("USERNAME")
.username("USERNAME")
.password("PASSWORD")
.build();
Database database = client.database("DATABASE_NAME", false);
View view = database.getViewRequestBuilder("DESIGN_DOC_NAME", "VIEW_NAME")
.newFindByIndexOptions()
.reduce(true)
.build();
try {
double average = (Double) view.getResponse().getRows().get(0).getValue();
System.out.println("Average: " + average);
} catch (NoDocumentException e) {
System.out.println("No documents found for the view.");
}
}
}
4. 最大值聚合查询:
import com.cloudant.client.api.ClientBuilder;
import com.cloudant.client.api.CloudantClient;
import com.cloudant.client.api.Database;
import com.cloudant.client.api.model.FindByIndexOptions;
import com.cloudant.client.org.lightcouch.NoDocumentException;
import com.cloudant.client.org.lightcouch.View;
public class AggregateQueriesExample {
public static void main(String[] args) {
CloudantClient client = ClientBuilder.account("USERNAME")
.username("USERNAME")
.password("PASSWORD")
.build();
Database database = client.database("DATABASE_NAME", false);
View view = database.getViewRequestBuilder("DESIGN_DOC_NAME", "VIEW_NAME")
.newFindByIndexOptions()
.reduce(true)
.build();
try {
double max = (Double) view.getResponse().getRows().get(0).getValue();
System.out.println("Maximum: " + max);
} catch (NoDocumentException e) {
System.out.println("No documents found for the view.");
}
}
}
这些示例代码中的"USERNAME"和"PASSWORD"应该替换为正确的IBM Cloudant凭据信息，"DATABASE_NAME"替换为要进行聚合查询的数据库名称。同时，"DESIGN_DOC_NAME"和"VIEW_NAME"需要替换为实际的设计文档和视图名称。
请注意，实际聚合查询的设计和视图需要在IBM Cloudant的Web界面上进行设置。这些示例代码只是演示如何执行聚合查询。
