使用Java实现Neo4j聚合查询
要使用Java实现Neo4j的各种聚合查询，首先需要在项目中添加Neo4j的驱动依赖。Neo4j提供了官方的Java驱动，可以通过Maven添加以下依赖：
<dependencies>
<dependency>
<groupId>org.neo4j.driver</groupId>
<artifactId>neo4j-java-driver</artifactId>
<version>4.3.7</version>
</dependency>
</dependencies>
然后，你可以使用以下Java代码实现各种数据聚合查询：
1. 计数查询
import org.neo4j.driver.*;
import static org.neo4j.driver.Values.parameters;
public class CountQueryExample {
public static void main(String[] args) {
try (Driver driver = GraphDatabase.driver("bolt://localhost:7687", AuthTokens.basic("username", "password"));
Session session = driver.session()) {
String query = "MATCH (n:Person) RETURN count(n) AS count";
Result result = session.run(query);
while (result.hasNext()) {
Record record = result.next();
System.out.println(record.get("count").asInt());
}
}
}
}
2. 最大值查询
import org.neo4j.driver.*;
import static org.neo4j.driver.Values.parameters;
public class MaxQueryExample {
public static void main(String[] args) {
try (Driver driver = GraphDatabase.driver("bolt://localhost:7687", AuthTokens.basic("username", "password"));
Session session = driver.session()) {
String query = "MATCH (n:Person) RETURN max(n.age) AS maxAge";
Result result = session.run(query);
while (result.hasNext()) {
Record record = result.next();
System.out.println(record.get("maxAge").asInt());
}
}
}
}
3. 平均值查询
import org.neo4j.driver.*;
import static org.neo4j.driver.Values.parameters;
public class AverageQueryExample {
public static void main(String[] args) {
try (Driver driver = GraphDatabase.driver("bolt://localhost:7687", AuthTokens.basic("username", "password"));
Session session = driver.session()) {
String query = "MATCH (n:Person) RETURN avg(n.age) AS averageAge";
Result result = session.run(query);
while (result.hasNext()) {
Record record = result.next();
System.out.println(record.get("averageAge").asDouble());
}
}
}
}
4. 求和查询
import org.neo4j.driver.*;
import static org.neo4j.driver.Values.parameters;
public class SumQueryExample {
public static void main(String[] args) {
try (Driver driver = GraphDatabase.driver("bolt://localhost:7687", AuthTokens.basic("username", "password"));
Session session = driver.session()) {
String query = "MATCH (n:Person) RETURN sum(n.age) AS totalAge";
Result result = session.run(query);
while (result.hasNext()) {
Record record = result.next();
System.out.println(record.get("totalAge").asInt());
}
}
}
}
这些示例代码演示了如何使用Java实现Neo4j的各种聚合查询。你可以根据自己的需求修改这些代码，并根据实际的Neo4j数据库配置进行连接。记得用正确的用户名和密码替换代码中的占位符。
