一、IDEA新建Maven项目添加依赖
<properties>
<neo4j.version>3.4.1</neo4j.version>
</properties>
<dependencies>
<dependency>
<!-- This gives us the Procedure API our runtime code uses.
We have a `provided` scope on it, because when this is
deployed in a Neo4j Instance, the API will be provided
by Neo4j. If you add non-Neo4j dependencies to this
project, their scope should normally be `compile` -->
<groupId>org.neo4j</groupId>
<artifactId>neo4j</artifactId>
<version>${neo4j.version}</version>
<scope>provided</scope>
</dependency>
<!-- Test Dependencies -->
<dependency>
<!-- This is used for a utility that lets us start Neo4j with
a specific Procedure, which is nice for writing tests. -->
<groupId>org.neo4j.test</groupId>
<artifactId>neo4j-harness</artifactId>
<version>${neo4j.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<!-- Used to send cypher statements to our procedure. -->
<groupId>org.neo4j.driver</groupId>
<artifactId>neo4j-java-driver</artifactId>
<version>1.4.2</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.47</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<!-- Neo4j Procedures require Java 8 -->
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<!-- This generates a jar-file with our procedure code,
plus any dependencies marked as `compile` scope.
This should then be deployed in the `plugins` directory
of each Neo4j instance in your deployment.
After a restart, the procedure is available for calling. -->
<artifactId>maven-shade-plugin</artifactId>
<version>2.4.3</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
二、需要排序的查询
需要排序的关系p，其中关系r上有属性eventTargetIds属性值是ids（由ID拼接成的string，使用逗号分隔）
eg.eventTargetIds:123123,123123,2131,12321,23424,123123,2331
zdr.apoc.getEventIdsSize是自定义的函数
RETURN zdr.apoc.getEventIdsSize("123123,123123,2131,12321,23424,123123,2331") as value; // 返回长度
match p=(n:Event)<-[r:HAS]-(m:VirId) where n.name='新闻_1432' and r.eventTargetIds IS NOT NULL return p ORDER BY zdr.apoc.getEventIdsSize(r.eventTargetIds) DESC limit 10上述排序也可以使用Neo4j自带的size()函数
match p=(n:Event)<-[r:HAS]-(m:VirId) where n.name='新闻_1432' and r.eventTargetIds IS NOT NULL return p ORDER BY size(r.eventTargetIds) DESC limit 10
三、编写zdr.apoc.getEventIdsSize函数
自定义函数可以根据需求实现更多更实用的功能，除此之外还可以一定程度上优化查询速度，因此还是很强大的。
public class ZdrProcedures {
/**
* @param
* @return
* @Description: TODO(获取关系的属性ids的长度 ， ids的值是用逗号分隔的id)
*/
@UserFunction(name = "zdr.apoc.getEventIdsSize")// name是给函数设置别名
public Number getEventIdsSize(@Name("ids") String ids) {
String[] array = ids.split(",");
int eventIdsSize = array.length;
return eventIdsSize;
}
}// 测试函数
public class ZdrProceduresTest {
@Rule
public Neo4jRule neo4j = new Neo4jRule().withFunction(ZdrProcedures.class);
@Test
public void getEventIdsSize() throws Exception {
GraphDatabaseService db = neo4j.getGraphDatabaseService();
try (Transaction tx = db.beginTx()) {
String eventIds = "123213,234324,4354353,1231231,2132131";
Map<String, Object> params = new HashMap<>();
params.put("eventIds", eventIds);
Result result = db.execute("RETURN zdr.apoc.getEventIdsSize({eventIds}) as value", params);
int eventIdsSize = (int) result.next().get("value");
System.out.println(eventIdsSize);
}
}
}
四、测试完成之后打包安装到Neo4j就可以开始愉快的使用了！
Neo4j图数据库APOC存储过程基本安装使用参考链接
