neo4j(1)Introduction to neo4j and sample project

neo4j(1)Introduction to neo4j and sample project

1. Introduction to Graph Database
Node ------relationship -------> property
name=wheel     number=4        name=car,color=red,

A Graph --- records data in ---->Nodes -----which have ----> Properties
Nodes ------are organized by -----> Relationships ---- which also have -----> Properties

A Traversal ---- navigates ----> a Graph; it ----identifies ---> Paths ---- which order -----> Nodes
An Index ----maps from ----> Properties ---to either ----> Nodes or Relationships

A Graph Database ---- manages a ----> Graph and ----also manages related ---> Indexs

2. The domain Layer
The User Object
@NodeEntity
public class Userneo4j {

@GraphId
private Long id;

private String firstName;
private String lastName;

@Indexed
private String username;
private String password;

@Fetch @RelatedTo(type = "HAS_ROLENEO4J")
private Roleneo4j roleneo4j;

public Userneo4j() {}

public Userneo4j(String username) {
this.username = username;
}

public Userneo4j(String username, String firstName, String lastName, Roleneo4j roleneo4j) {
this.username = username;
this.firstName = firstName;
this.lastName = lastName;
this.roleneo4j = roleneo4j;
}

public Userneo4j(String username, String password, String firstName, String lastName, Roleneo4j roleneo4j) {
this.username = username;
this.password = password;
this.firstName = firstName;
this.lastName = lastName;
this.roleneo4j = roleneo4j;
}
...snip...

The Role domain:
@NodeEntity
public class Roleneo4j {

@GraphId
private Long id;
private Userneo4j userneo4j;
private Integer role;

public Roleneo4j() {
}

public Roleneo4j(Integer role) {
this.role = role;
}
...snip...

The relationship domain object:
@RelationshipEntity(type = "HAS_ROLENEO4J")
public class Userneo4jRoleneo4jRelationship {

private String description;

@StartNode
private Userneo4j userneo4j;

@EndNode
private Roleneo4j roleneo4j;
...snip...

@NodeEntity annotation is used to turn a POJO class into an entity backed by a node in the graph database. Fields on the entity are by default mapped to properties of the node.

@GraphId
For the simple mapping this is a required field which must be of type Long. It is used by Spring Data Neo4j to store the node or relationship-id to re-connect the entity to the graph.

The @Indexed annotation can be declared on fields that are intended to be indexed by the Neo4j indexing facilities.

@Fetch
To have the collections of relationships being read eagerly ... we have to annotate it with the @Fetch annotation.

@RelatedTo: Connecting node entities
Every field of a node entity that references one or more other node entities is backed by relationships in the graph.

@RelationshipEntity, making them relationship entities. Just as node entities represent nodes in the graph, relationship entities represent relationships.

3. The Service Layer
Init Service to add the init data:
package com.sillycat.easynosql.dao.neo4j.init;

import org.springframework.beans.factory.annotation.Autowired;

import com.sillycat.easynosql.dao.neo4j.model.Roleneo4j;
import com.sillycat.easynosql.dao.neo4j.model.Userneo4j;
import com.sillycat.easynosql.dao.neo4j.repository.Userneo4jRepository;

public class InitNeo4jService {

@Autowired
private Userneo4jRepository userneo4jRepository;

public void init() {
if (userneo4jRepository.findByUsername("john") != null) {
userneo4jRepository.delete(userneo4jRepository
.findByUsername("john"));
}

if (userneo4jRepository.findByUsername("jane") != null) {
userneo4jRepository.delete(userneo4jRepository
.findByUsername("jane"));
}

// Create new records
Userneo4j john = new Userneo4j();
john.setFirstName("John");
john.setLastName("Smith");
john.setPassword("111111");
john.setRoleneo4j(new Roleneo4j(1));
john.setUsername("john");

Userneo4j jane = new Userneo4j();
jane.setFirstName("Jane");
jane.setLastName("Adams");
jane.setPassword("111111");
jane.setRoleneo4j(new Roleneo4j(2));
jane.setUsername("jane");

john.getRoleneo4j().setUserneo4j(john);
jane.getRoleneo4j().setUserneo4j(jane);

userneo4jRepository.save(john);
userneo4jRepository.save(jane);

userneo4jRepository.findByUsername("john").getRoleneo4j().getRole();
}

}

The Service will access the data via repository classes:
package com.sillycat.easynosql.service.impl;

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.neo4j.conversion.EndResult;

import com.sillycat.easynosql.dao.neo4j.model.Userneo4j;
import com.sillycat.easynosql.dao.neo4j.repository.Roleneo4jRepository;
import com.sillycat.easynosql.dao.neo4j.repository.Userneo4jRepository;
import com.sillycat.easynosql.model.User;
import com.sillycat.easynosql.model.convert.UserConvert;
import com.sillycat.easynosql.service.UserService;

public class UserServiceNeo4jImpl implements UserService{

@Autowired
private Userneo4jRepository userneo4jRepository;

@Autowired
private Roleneo4jRepository roleneo4jRepository;

public User create(User user) {
Userneo4j existingUser = userneo4jRepository.findByUsername(user
.getUsername());

if (existingUser != null) {
throw new RuntimeException("Record already exists!");
}
Userneo4j saveUser = UserConvert.convertUser2Userneo4j(user);
saveUser.getRoleneo4j().setUserneo4j(saveUser);
userneo4jRepository.save(saveUser);
return UserConvert.convertUserneo4j2User(saveUser);
}

public User read(User user) {
Userneo4j existingUser = userneo4jRepository.findByUsername(user
.getUsername());
user = UserConvert.convertUserneo4j2User(existingUser);
return user;
}

public List<User> readAll() {
List<User> users = new ArrayList<User>();

EndResult<Userneo4j> results = userneo4jRepository.findAll();
for (Userneo4j r : results) {
users.add(UserConvert.convertUserneo4j2User(r));
}

return users;
}

public User update(User user) {
Userneo4j existingUser = userneo4jRepository.findByUsername(user
.getUsername());

if (existingUser == null) {
return null;
}

existingUser.setFirstName(user.getFirstName());
existingUser.setLastName(user.getLastName());
existingUser.getRoleneo4j().setRole(user.getRole().getRole());

roleneo4jRepository.save(existingUser.getRoleneo4j());
userneo4jRepository.save(existingUser);
return UserConvert.convertUserneo4j2User(existingUser);
}

public Boolean delete(User user) {
Userneo4j existingUser = userneo4jRepository.findByUsername(user
.getUsername());

if (existingUser == null) {
return false;
}

userneo4jRepository.delete(existingUser);
return true;
}

}

references:
http://www.infoq.com/cn/articles/graph-nosql-neo4j
http://krams915.blogspot.com/2012/03/spring-mvc-31-implement-crud-with_3045.html
https://github.com/krams915/spring-neo4j-tutorial.git
http://neo4j.org/
http://www.iteye.com/topic/978371
http://agapple.iteye.com/blog/1128400
http://blog.csdn.net/jdream314/article/details/6633655
http://hi.baidu.com/luohuazju/blog/item/085eff062ac71475020881d3.html