Spring Boot 轻易访问Neo4j

在Spring Boot中访问Neo4j，经过Spring Data Neo4j能够轻易地实现。

例如，现有以下图所示的数据模型：

这表示有两个节点：用户和组，而且这两个节点的关系是从属关系，即用户从属于组。

根据这个数据模型，使用Spring Data Neo4j进行建模。

首先，在项目工程中引用Spring Boot的依赖，以下所示：

<properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.2.RELEASE</version>
        <relativePath/>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

而后，在Neo4j模块引用Neo4j的依赖，以下所示：

<dependencies>
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-neo4j</artifactId>
        </dependency>
        <dependency>
            <groupId>org.neo4j</groupId>
            <artifactId>neo4j-ogm-embedded-driver</artifactId>
            <version>2.0.5</version>
        </dependency>
        <dependency>
            <groupId>org.neo4j</groupId>
            <artifactId>neo4j-ogm-bolt-driver</artifactId>
            <version>2.0.5</version>
        </dependency>
    </dependencies>

上面依赖包下载完成后，就可使用Spring Data Neo4j进行建模和实现数据持久化。

用户节点建模：

package com.demo.neo4j.domain;

import org.neo4j.ogm.annotation.GraphId;
import org.neo4j.ogm.annotation.NodeEntity;
import org.neo4j.ogm.annotation.Relationship;

@NodeEntity
public class User {
   @GraphId
   private Long id;
   private String name;

   @Relationship(type = "从属", direction = Relationship.OUTGOING)
   private Group group;

   public User() {
   }

   public Long getId() {
      return id;
   }

   public void setId(Long id) {
      this.id = id;
   }

   public String getName() {
      return name;
   }

   public void setName(String name) {
      this.name = name;
   }

   public Group getGroup() {
      return group;
   }

   public void setGroup(Group group) {
      this.group = group;
   }
}

组节点建模：

package com.demo.neo4j.domain;

import org.neo4j.ogm.annotation.GraphId;

public class Group {
    @GraphId
    private Long id;
    private String name;

    public Group() {
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

数据持久化设计：

package com.demo.neo4j.repository;

import com.demo.neo4j.domain.User;
import org.springframework.data.neo4j.repository.GraphRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends GraphRepository<User> {
    User findByName(String name);
}

为了让上面设计生效，须要对使用的Spring Data Neo4j进行配置：

package com.demo.neo4j.config;

import org.neo4j.ogm.session.SessionFactory;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.neo4j.config.Neo4jConfiguration;
import org.springframework.data.neo4j.repository.config.EnableNeo4jRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@Configuration
@EnableNeo4jRepositories(basePackages = { "com.demo.neo4j.repository" })
@EnableTransactionManagement
public class Neo4jConfig extends Neo4jConfiguration {

    @Override
    public SessionFactory getSessionFactory() {
        return new SessionFactory("com.demo.neo4j.domain");
    }

}

链接Neo4j数据库，可使用2.x或3.x版本，或者不用安装服务器，直接使用嵌入式数据库。

使用嵌入式方式链接数据库，编辑以下内容到ogm.properties文件，并将文件保存到资源目录中：

compiler=org.neo4j.ogm.compiler.MultiStatementCypherCompiler
driver=org.neo4j.ogm.drivers.embedded.driver.EmbeddedDriver
URI=file:///test/graph.db

最后使用以下测试用例进行测试：

package com.demo.neo4j.test;

import com.demo.neo4j.config.Neo4jConfig;
import com.demo.neo4j.domain.Group;
import com.demo.neo4j.domain.User;
import com.demo.neo4j.repository.UserRepository;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.util.Assert;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {Neo4jConfig.class})
public class Neo4jTest {
    private static Logger log = LoggerFactory.getLogger(Neo4jTest.class);

    @Autowired
    private UserRepository userRepository;

    @Before
    public void addData() {
        Group group = new Group();
        group.setName("admins");

        User user = new User();
        user.setName("admin");
        user.setGroup(group);

        userRepository.save(user);
        Assert.notNull(user.getId());
    }

    @Test
    public void getData() {
        User user = userRepository.findByName("admin");
        Assert.notNull(user);
        log.info("\n================== user name={}; group name={} ==================",
                user.getName(), user.getGroup().getName());
    }
}

运行测试用例经过，并可看到以下结果：

================== user name=admin; group name=admins ==================