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Example for using Neo4j with Grails

In reply to my today’s annoncement of the Neo4j Grails plugin, @StigLau asked me to provide an example for using the Neo4j Grails plugin. So here we go:

  1. Create your sample application: 
    grails create-app neo4jtest; cd neo4jtest
  2. Add the Neo4j plugin: 
    grails install-plugin neo4j
  3. create some sample domain classes: 
    grails create-domain-class Author
grails create-domain-class Book
  4. create a controller for the domain class 
    grails create-controller Author
grails create-controller Book
  5. modify the domain classes: 
    import grails.plugins.neo4j.Neo4jEntity
@Neo4jEntity
class Author {
    String name
    Date dob

    static hasMany = [ books: Book ]
}

    and

    import grails.plugins.neo4j.Neo4jEntity
@Neo4jEntity
class Book {
    String title
    static belongsTo = [author:Author]
}
  6. modify the controller to use dynamic scaffolding: 
    class AuthorController {
    def scaffold = true
}
    class BookController {
    def scaffold = true
}
  7. start up the application: 
    grails run-app
  8. use it, love it: go to http://localhost:8080/neo4jtest, add some authors and books.
  9. to explore the Neo4j node space created with your grails app, check out Neoclipse.

UPDATE: Use Grails 1.2.1

20 replies on “Example for using Neo4j with Grails”

Hi Stefan, I’ve tried your example but I get a Java Error “The type Node is ambiguous” repeated 5 times in the class Neo4jPluggingSupport. It seems that others are able to use your example without problem so I suspect that my IDE may be the problem. I’m using springsource’s STS 2.3.1 (Eclipse 3.5, Grails 1.2.1, Groovy 1.7).

I wanted to ask your opinion on this before creating an issue at codehaus for GRECLIPSE.

Thanks!

/ricardo

Hi Stefan, i was trying to use neo4j plugin 0.3.1 with grails 1.3.7 and 1.1 neo4j db. Getting error at entity annotation, please help me.

error
==
Groovy:class grails.plugins.neo4j.Neo4jEntity is not an annotation in @grails.plugins.neo4j.Neo4jEntity

If using from an IDE, make sure neo4jplugin’s src/ast directory is a source folder – that’s where Neo4jEntity annotation is located. If running grails run-app, do you see a line like ‘Precompiling neo4j plugin – required because of AST transformations…’ on stdout/stderr ?

By Post Author

Thanks Stefan.

I am using Eclipse IDE, i couldn’t find src/ast directory when i expanded plugin in eclipse.

However when i do run-app i see fallowing, it says “Precompiling neo4j plugin – required because of AST transformations” and app running..

how do i suppress eclipse error?

==
Welcome to Grails 1.3.7 – http://grails.org/
Licensed under Apache Standard License 2.0
Grails home is set to: C:\grails_project\springsource-tool-suite-2.6.1.SR1-e3.6.2-win32-x86_64\springsource\grails-1.3.7\

Base Directory: C:\grails_project\neotest
Resolving dependencies…
Dependencies resolved in 2560ms.
Running script C:\grails_project\springsource-tool-suite-2.6.1.SR1-e3.6.2-win32-x86_64\springsource\grails-1.3.7\scripts\RunApp.groovy
Environment set to development
[echo] plugin files: file [C:\Users\preet\.grails\1.3.7\projects\neotest\plugins\neo4j-0.3.1-SNAPSHOT\.]
[echo] Precompiling neo4j plugin – required because of AST transformations…
[echo] src C:/Users/preet/.grails/1.3.7/projects/neotest/plugins/neo4j-0.3.1-SNAPSHOT C:\Users\preet\.grails\1.3.7\projects\neotest\plugin-classes
[echo] done precompiling AST transformations
[exec] The command attribute is deprecated.
[exec] Please use the executable attribute and nested arg elements.
[exec] FIND: Parameter format not correct
[exec] Result: 2
[groovyc] Compiling 1 source file to C:\grails_project\neotest\target\classes
[delete] Deleting directory C:\Users\preet\.grails\1.3.7\projects\neotest\tomcat
Running Grails application..
Server running. Browse to http://localhost:8080/neotest

Thanks Stefan.

I am using SpringSource Tool Suite Version: 2.7.1.RELEASE, i couldn’t find src/ast under under plugin when i expand it.

However i see “done precompiling AST transformations” when i do run-app

How do i suppress IDE error at @Neo4jEntity?

Thankyou

Hi,

Thank you for this plugin.
I’ve one question : when I follow the example showed above, everything is working but the data are not saved in the graph : the org.codehaus.groovy.grails.plugins.neo4j.Neo4jController always show me an empty graph.

Should I modify the DataSource.groovy?
The example don’t speak about it.

Regards,
Jean-Sébastien Stoffen

Hi,
Thank you for your answer.
I’m interested in the new version of your plugin.
I’m discovering Grails Neo4j and Groovy.

I’m still wondering about something : when I create a new instance of an object using a Grails controller, I save it and the graph is not updated. It’s probably something to set in the DataSource.groovy.
Could you show me how to configure it?

Thank you,
Jean-Sébastien.

For some reason, I decided to use the latest of Neo4j and Grails which aren’t RELEASES but Milestones. NEO4j 1.5.M02 and Grails 2.0.0.RC1 and Spring-data-neo4j 2.0.0.M1. Do you think it is possible to use the plugin to set the basics and able to have Grails generate the scaffolding and Controllers. Then just add the newer features?

Thanks

Mark

I am getting below error with grails 2.3.5

| Error Compilation error: startup failed:
F:\git_projects\neo4jtest\grails-app\domain\neo4jtest\Author.groovy: 3: unable to resolve class grails.plugins.neo4j.Neo4jEntity
@ line 3, column 1.
import grails.plugins.neo4j.Neo4jEntity
^

F:\git_projects\neo4jtest\grails-app\domain\neo4jtest\Book.groovy: 3: unable to resolve class grails.plugins.neo4j.Neo4jEntity
@ line 3, column 1.
import grails.plugins.neo4j.Neo4jEntity
^

2 errors
| Error Error running script run-app: org.codehaus.groovy.grails.cli.ScriptExitException (Use –stacktrace to see the full trace)

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