Neo4j database for Grails app without using Neo4j GORM plugin - grails

Question

I want to make a web-app using Grails framework for the server part and Neo4j database for storage. I found the Neo4j GORM plugin on Grails site, but unfortunately after numerous attempts I could not make it work properly. If i solve one error I get more, i can't even set a basic app to work. So I would like to write my own code for handling CRUD operations. I would like to override the default CRUD operations for domain classes. For example when I save a Person entity, i would use the REST API offered by Neo4j database to store the entity there etc. Would this be an acceptable solution? If yes, then how should I proceed about overriding the CRUD methods for domain classes?
Problem i had with GORM plugin: I followed the steps described in the documentation : http://projects.spring.io/grails-data-mapping/neo4j/manual/guide/gettingStarted.html . I created a simple Grails web-app, included the Neo4j-GORM plugin dependency. The application started.
If I try to access 'org.grails.datastore.gorm.neo4j.Neo4jController' I get some strange errors:
Here are the errors I get in the console:
015-01-04 14:11:22,460 [http-bio-8080-exec-2] ERROR errors.GrailsExceptionResolver - NullPointerException occurred when processing request: [GET] /ANewHope/neo4j/node
Cannot invoke method getNodeById() on null object. Stacktrace follows:
Message: Cannot invoke method getNodeById() on null object
Line | Method
->> 30 | doCall in org.grails.datastore.gorm.neo4j.Neo4jController$_closure2
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 198 | doFilter in grails.plugin.cache.web.filter.PageFragmentCachingFilter
| 63 | doFilter in grails.plugin.cache.web.filter.AbstractFilter
| 1145 | runWorker in java.util.concurrent.ThreadPoolExecutor
| 615 | run . . . in java.util.concurrent.ThreadPoolExecutor$Worker
^ 745 | run in java.lang.Thread
Here is my BuildConfig.groovy:
grails.servlet.version = "3.0" // Change depending on target container compliance (2.5 or 3.0)
grails.project.class.dir = "target/classes"
grails.project.test.class.dir = "target/test-classes"
grails.project.test.reports.dir = "target/test-reports"
grails.project.work.dir = "target/work"
grails.project.target.level = 1.6
grails.project.source.level = 1.6
//grails.project.war.file = "target/${appName}-${appVersion}.war"
grails.project.fork = [
// configure settings for compilation JVM, note that if you alter the Groovy version forked compilation is required
// compile: [maxMemory: 256, minMemory: 64, debug: false, maxPerm: 256, daemon:true],
// configure settings for the test-app JVM, uses the daemon by default
test: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256, daemon:true],
// configure settings for the run-app JVM
run: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256, forkReserve:false],
// configure settings for the run-war JVM
war: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256, forkReserve:false],
// configure settings for the Console UI JVM
console: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256]
]
grails.project.dependency.resolver = "maven" // or ivy
grails.project.dependency.resolution = {
// inherit Grails' default dependencies
inherits("global") {
// specify dependency exclusions here; for example, uncomment this to disable ehcache:
// excludes 'ehcache'
}
log "error" // log level of Ivy resolver, either 'error', 'warn', 'info', 'debug' or 'verbose'
checksums true // Whether to verify checksums on resolve
legacyResolve false // whether to do a secondary resolve on plugin installation, not advised and here for backwards compatibility
repositories {
inherits true // Whether to inherit repository definitions from plugins
grailsPlugins()
grailsHome()
mavenLocal()
grailsCentral()
mavenCentral()
// uncomment these (or add new ones) to enable remote dependency resolution from public Maven repositories
//mavenRepo "http://repository.codehaus.org"
//mavenRepo "http://download.java.net/maven/2/"
//mavenRepo "http://repository.jboss.com/maven2/"
mavenRepo 'http://m2.neo4j.org/releases'
}
dependencies {
// specify dependencies here under either 'build', 'compile', 'runtime', 'test' or 'provided' scopes e.g.
// runtime 'mysql:mysql-connector-java:5.1.29'
// runtime 'org.postgresql:postgresql:9.3-1101-jdbc41'
test "org.grails:grails-datastore-test-support:1.0.2-grails-2.4"
}
plugins {
// plugins for the build system only
build ":tomcat:7.0.55"
// plugins for the compile step
compile ":neo4j:2.0.0-M02"
compile ":scaffolding:2.1.2"
compile ':cache:1.1.8'
compile ":asset-pipeline:1.9.9"
// plugins needed at runtime but not for compilation
// runtime ":hibernate4:4.3.6.1" // or ":hibernate:3.6.10.18"
//runtime ":database-migration:1.4.0"
runtime ":jquery:1.11.1"
// Uncomment these to enable additional asset-pipeline capabilities
//compile ":sass-asset-pipeline:1.9.0"
//compile ":less-asset-pipeline:1.10.0"
//compile ":coffee-asset-pipeline:1.8.0"
//compile ":handlebars-asset-pipeline:1.3.0.3"
}
}
Here is DataSource.groovy:
dataSource {
pooled = true
jmxExport = true
driverClassName = "org.h2.Driver"
username = "sa"
password = ""
}
//hibernate {
// cache.use_second_level_cache = true
// cache.use_query_cache = false
//// cache.region.factory_class = 'net.sf.ehcache.hibernate.EhCacheRegionFactory' // Hibernate 3
// cache.region.factory_class = 'org.hibernate.cache.ehcache.EhCacheRegionFactory' // Hibernate 4
// singleSession = true // configure OSIV singleSession mode
// flush.mode = 'manual' // OSIV session flush mode outside of transactional context
//}
//grails {
// neo4j {
// type = "embedded"
// location = "C:\\data\\neo4j"
// params = []
// }
//}
// environment specific settings
environments {
development {
dataSource {
dbCreate = "create-drop" // one of 'create', 'create-drop', 'update', 'validate', ''
url = "jdbc:h2:mem:devDb;MVCC=TRUE;LOCK_TIMEOUT=10000;DB_CLOSE_ON_EXIT=FALSE"
}
}
test {
dataSource {
dbCreate = "update"
url = "jdbc:h2:mem:testDb;MVCC=TRUE;LOCK_TIMEOUT=10000;DB_CLOSE_ON_EXIT=FALSE"
}
}
production {
dataSource {
dbCreate = "update"
url = "jdbc:h2:prodDb;MVCC=TRUE;LOCK_TIMEOUT=10000;DB_CLOSE_ON_EXIT=FALSE"
properties {
// See http://grails.org/doc/latest/guide/conf.html#dataSource for documentation
jmxEnabled = true
initialSize = 5
maxActive = 50
minIdle = 5
maxIdle = 25
maxWait = 10000
maxAge = 10 * 60000
timeBetweenEvictionRunsMillis = 5000
minEvictableIdleTimeMillis = 60000
validationQuery = "SELECT 1"
validationQueryTimeout = 3
validationInterval = 15000
testOnBorrow = true
testWhileIdle = true
testOnReturn = false
jdbcInterceptors = "ConnectionState"
defaultTransactionIsolation = java.sql.Connection.TRANSACTION_READ_COMMITTED
}
}
}
}
After this I tried to specify the location as suggested in the documentation and added the following to DataSource.groovy:
grails {
neo4j {
type = "embedded"
location = "C:\\data\\neo4j"
params = []
}
}
The result was the same. After failed attempts I decided to try some other solution.
I want to use Neo4j for my Bachelor Thesis project, and my professor suggested me to use it with Grails. I like both Neo4j and Grails, but unfortunately I got into this problem when I tried to use them together.

Answer 1

If you don't want to use the GORM plugin, you could for instance use the Neo4j-JDBC driver from Grails to send parameterized Cypher Statements to the server. Much like you would do with a relational database.
There is also a new ORM in the works but it is still very much work in progress. You can find it here: https://github.com/neo4j/neo4j-ogm

Answer 2

As powerful as the GORM is, it isn't right for every project. I often elect to use something else, however, grails expects that anything in the domain directory is going to be using the GORM. If you want to use a different API you should just put your classes in src/groovy. If you still want to be able to use constraints for validation, you can apply the #Validatable annotation to the class. Details on that can be found in the Validation Grails docs. I would then just put all of your code to interface with the Neo4j REST API into a Grails Service.