Neo4j OGM学习和体验

Neo4j OGM

• Neo4j OGM（Object-Graph Mapping）是一个用于在Java应用程序中与Neo4j图数据库交互的库。它能够将对象模型与图数据模型之间进行映射，使得开发者可以更加方便地对图数据进行操作，而无需编写大量的Cypher查询语句。
• Neo4j OGM 提供了一个简洁的API，帮助开发者通过对象的方式来处理图数据，这样能够使代码更加清晰和易于维护。

核心概念

1. 对象映射：Neo4j OGM 提供了将数据库中的节点和关系映射到Java对象的能力。开发者可以通过简单的注释来定义对象之间的映射关系。例如，可以使用 @NodeEntity 注解来表示一个节点实体，使用 @Relationship 注解来表示关系。
2. 会话管理：Neo4j OGM 使用会话来管理数据的读取和写入。每个会话可以看作是一个与数据库的连接，开发者通过会话来执行CRUD操作（创建、读取、更新和删除），并处理对象的生命周期。
3. 查询：虽然 OGM 封装了大部分操作，但它依然支持使用 Cypher 查询来进行复杂的数据操作。开发者可以直接通过 OGM 的接口来执行 Cypher 查询，返回对象。

Neo4j OGM体验

项目地址

• neo4jAPILearn

Neo4j数据准备

• 使用Neo4j官方电影案例
  
  

1. 添加Maven依赖，在 pom.xml 中添加如下依赖：

<dependencies><dependency><groupId>org.neo4j</groupId><artifactId>neo4j-ogm-core</artifactId><version>4.0.15</version></dependency><dependency><groupId>org.neo4j</groupId><artifactId>neo4j-ogm-bolt-driver</artifactId><version>4.0.15</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.36</version><scope>provided</scope></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.13.2</version><scope>test</scope></dependency>
</dependencies>

2. 配置：创建SessionFactoryUtils类

import lombok.Getter;
import org.neo4j.ogm.config.Configuration;
import org.neo4j.ogm.session.SessionFactory;public class SessionFactoryUtils {private static final Configuration configuration=new Configuration.Builder().uri("bolt://neo4j:neo4jneo4j@192.168.1.21:7687").connectionPoolSize(150).connectionLivenessCheckTimeout(100).build();@Getterprivate static SessionFactory sessionFactory=new SessionFactory(configuration,"com.yang.ogm.pojo");
}

3. 创建实体:Movie，MyPerson，ActedIn

• Movie

import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import lombok.ToString;
import org.neo4j.ogm.annotation.*;import java.util.List;@NodeEntity
@Setter
@Getter
@NoArgsConstructor
@ToString
public class Movie {@Id@GeneratedValueprivate Long id;private String title;private Long released;@Property("tagline")private String tagLine;//设置关系并且指定方向@Relationship(type = "ACTED_IN",direction = Relationship.Direction.INCOMING)private List<ActedIn> actedIns;
}

• MyPerson

import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import lombok.ToString;
import org.neo4j.ogm.annotation.*;import java.util.List;@NodeEntity(label="Person")
@Setter
@Getter
@NoArgsConstructor
@ToString
public class MyPerson {@Id@GeneratedValueprivate Long id;private String name;private Long born;//指定关系//@Relationship(type = "ACTED_IN",direction = Relationship.Direction.OUTGOING)//private List<Movie> movies;@Relationship(type = "ACTED_IN")private List<ActedIn> actedIns;//导演关系@Relationship(type = "DIRECTED")private List<Movie> directedMovies;//出品关系@Relationship(type = "PRODUCED")private List<Movie> producedMovies;//写作关系@Relationship(type = "WROTE")private List<Movie> wroteMovies;
}

• ActedIn

import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import lombok.ToString;
import org.neo4j.ogm.annotation.*;@RelationshipEntity(type = "ACTED_IN")
@Setter
@Getter
@ToString(exclude = {"person","movie"})
@NoArgsConstructor
public class ActedIn {@Id@GeneratedValueprivate Long id;@StartNode //关系中的开始节点private MyPerson person;@EndNode  //关系中的结束节点private Movie movie;private String[] roles;
}

4. Person操作的服务层PersonService

import com.yang.ogm.pojo.MyPerson;
import com.yang.ogm.session.SessionFactoryUtils;
import org.neo4j.ogm.cypher.ComparisonOperator;
import org.neo4j.ogm.cypher.Filter;
import org.neo4j.ogm.model.Result;
import org.neo4j.ogm.session.Session;import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;public class PersonService {private Session session;public PersonService() {this.session = SessionFactoryUtils.getSessionFactory().openSession();}/*** 根据id查询用户数据* @param id* @return*/public MyPerson queryPersonById(Long id) {return this.session.load(MyPerson.class, id);}public void savePerson(MyPerson person) {this.session.save(person);}public void deletePerson(MyPerson person) {this.session.delete(person);}public ArrayList<Long> deletePersonByName(String name) {Filter filter = new Filter("name", ComparisonOperator.EQUALS,name);return (ArrayList<Long>) this.session.delete(MyPerson.class,List.of(filter),true);}// depth默认为1。 -1加载全部数据 0仅加载当前节点属性 1加载实例将映射该对象的简单属性及其直接相关的对象public MyPerson queryPersonById(Long id, int depth) {return this.session.load(MyPerson.class,id,depth);}public List<MyPerson> queryPersonByName(String name) {Filter filter = new Filter("name",ComparisonOperator.EQUALS,name);return (List<MyPerson>) this.session.loadAll(MyPerson.class, filter);}public Result queryAllShortestPathsByCypher(String personName1, String persoName2){String cypher="""match(n:Person {name:$personName1}),(m:Person {name:$personName2}),p=allShortestPaths((n)-[*]-(m))return p""";HashMap<String, String> params = new HashMap<>();params.put("personName1", personName1);params.put("personName2", persoName2);return this.session.query(cypher,params);}
}

5. CRUD 操作

import com.yang.ogm.pojo.Movie;
import com.yang.ogm.pojo.MyPerson;
import com.yang.ogm.service.PersonService;
import com.yang.ogm.session.SessionFactoryUtils;
import org.junit.Test;
import org.neo4j.driver.internal.InternalPath;
import org.neo4j.ogm.model.Result;
import org.neo4j.ogm.session.SessionFactory;import java.util.List;public class TestPersonService {private PersonService personService=new PersonService();@Testpublic void getSessionFactory(){SessionFactory sessionFactory = SessionFactoryUtils.getSessionFactory();System.out.println(sessionFactory);}@Testpublic void testQueryPersonById(){MyPerson myPerson = this.personService.queryPersonById(33L,2);System.out.println(myPerson);}@Testpublic void testQueryPersonByName(){List<MyPerson> list = this.personService.queryPersonByName("Tom Hanks");System.out.println(list);}@Testpublic void testQueryPersonByCypher(){Result result = this.personService.queryAllShortestPathsByCypher("Susan Sarandon", "Jessica Thompson");result.forEach(stringObjectMap -> {InternalPath.SelfContainedSegment[] arrays=(InternalPath.SelfContainedSegment[]) stringObjectMap.get("p");for (InternalPath.SelfContainedSegment segment : arrays) {System.out.println(segment);}});}@Testpublic void testSavePerson(){MyPerson myPerson = new MyPerson();myPerson.setName("沈腾");myPerson.setBorn(1970L);Movie movie = new Movie();movie.setTitle("飞驰人生");movie.setReleased(2019L);//添加关系 注意修改MyPerson类中的执行关系代码// myPerson.setMovies(List.of(movie));//// this.personService.savePerson(myPerson);// System.out.println(myPerson);}@Testpublic void testUpdate() {List<MyPerson> personList = personService.queryPersonByName("沈腾");MyPerson person = personList.get(0);person.setBorn(1980L);personService.savePerson(person);}@Testpublic void testDeletePersonByNmae() {Object result = personService.deletePersonByName("沈腾");System.out.println(result);}}