HazelcastJsonValue 是 Hazelcast 提供的用于表示 JSON 数据的类
以下是一个简单的示例,说明如何在 HazelcastJsonValue 中使用聚合:
在您的项目中添加 Hazelcast 依赖项。如果您使用 Maven,请将以下内容添加到 pom.xml 文件中:
<dependency>
<groupId>com.hazelcast</groupId>
<artifactId>hazelcast</artifactId>
<version>4.2</version>
</dependency>
import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.HazelcastInstance;
public class HazelcastExample {
public static void main(String[] args) {
HazelcastInstance hz = Hazelcast.newHazelcastInstance();
}
}
import com.hazelcast.core.HazelcastJsonValue;
public class HazelcastExample {
public static void main(String[] args) {
HazelcastInstance hz = Hazelcast.newHazelcastInstance();
HazelcastJsonValue jsonObject = new HazelcastJsonValue("{\"name\":\"John\", \"age\":30}");
}
}
import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.HazelcastInstance;
import com.hazelcast.core.IMap;
public class HazelcastExample {
public static void main(String[] args) {
HazelcastInstance hz = Hazelcast.newHazelcastInstance();
IMap<String, HazelcastJsonValue> map = hz.getMap("jsonValues");
HazelcastJsonValue jsonObject = new HazelcastJsonValue("{\"name\":\"John\", \"age\":30}");
map.put("exampleJson", jsonObject);
HazelcastJsonValue retrievedJsonObject = map.get("exampleJson");
System.out.println("Retrieved JSON: " + retrievedJsonObject.toString());
}
}
Hazelcast 提供了 IMap
接口的聚合方法,如 aggregate()
。要使用这些方法,您需要使用 HazelcastAggregationService
。以下是一个使用聚合函数的示例:
import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.HazelcastInstance;
import com.hazelcast.core.IMap;
import com.hazelcast.aggregation.impl.StringMaxAggregation;
public class HazelcastExample {
public static void main(String[] args) {
HazelcastInstance hz = Hazelcast.newHazelcastInstance();
IMap<String, HazelcastJsonValue> map = hz.getMap("jsonValues");
HazelcastJsonValue jsonObject1 = new HazelcastJsonValue("{\"name\":\"John\", \"age\":30}");
HazelcastJsonValue jsonObject2 = new HazelcastJsonValue("{\"name\":\"Jane\", \"age\":25}");
map.put("json1", jsonObject1);
map.put("json2", jsonObject2);
StringMaxAggregation stringMaxAggregation = new StringMaxAggregation("name");
String maxValue = map.aggregate(stringMaxAggregation);
System.out.println("Max name value: " + maxValue);
}
}
在这个示例中,我们使用了 StringMaxAggregation
聚合函数来获取 name 属性的最大值。您可以使用其他聚合函数,如 StringMinAggregation
、LongSumAggregation
等,根据您的需求进行操作。
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