Neo4j database for the Grails application without using the Neo4j GORM plugin

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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.


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