Problem with creating an object in neo4j

Question

I am using the django integration for neo4j and I'm getting the following traceback when I'm trying to create a node.
I do have JPype installed and it can be imported.

 p = Person.objects.create(first_name='omer', last_name='katz')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 138, in create
    return self.get_query_set().create(**kwargs)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/model/django_model/__init__.py", line 362, in create
    obj.save(force_insert=True)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 460, in save
    self.save_base(using=using, force_insert=force_insert, force_update=force_update)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_util.py", line 47, in __get__
    method, graphdb = self.descr_get(obj, cls)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_util.py", line 41, in descr_get
    graphdb = self.accessor.__get__(obj, cls)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/model/django_model/__init__.py", line 58, in __get__
    return DjangoNeo.neo
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/model/django_model/__init__.py", line 124, in neo
    return self.__setup_neo()
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/model/django_model/__init__.py", line 136, in __setup_neo
    self.__neo = NeoService(resource_uri, **options)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/__init__.py", line 522, in __new__
    neo = core.load_neo(resource_uri, params)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_core.py", line 180, in load_neo
    backend.initialize(**parameters)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 61, in initialize
    raise ImportError("No applicable backend found.")
ImportError: No applicable backend found.

EDIT:
As requested here are my neo4j settings:

NEO4J_RESOURCE_URI = '/var/neo4j/neo4django'
# NEO4J_RESOURCE_URI should be the path to where
#    you want to store the Neo4j database.

NEO4J_OPTIONS = {
    # this is optional and can be used to specify
    # extra startup parameters for Neo4j, such as
    # the classpath to load Neo4j from.
}

EDIT:
After following thobe's suggestion I get the following when I try to import my own models:

    ERROR:root:Importing native backends failed.
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
        embedded, remote = implementation.initialize(classpath, params)
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
        jvm = jpype.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
        return _linux.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
        jvm = _getJVMFromJavaHome()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
        if os.path.exists(java_home+"/bin/javac") :
    TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
    ERROR:root:Importing native backends failed.
    Traceback (most recent call last):
      FERROR:root:Importing native backends failed.
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
        embedded, remote = implementation.initialize(classpath, params)
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
        jvm = jpype.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
        return _linux.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
        jvm = _getJVMFromJavaHome()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
        if os.path.exists(java_home+"/bin/javac") :
    TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
    ERROR:root:Importing native backends failed.
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
        embedded, remote = implementation.initialize(classpath, params)
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
        jvm = jpype.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
        return _linux.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
        jvm = _getJVMFromJavaHome()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
        if os.path.exists(java_home+"/bin/javac") :
    TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
    ERROR:root:Importing native backends failed.
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
        embedded, remote = implementation.initialize(classpath, params)
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
        jvm = jpype.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
        return _linux.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
        jvm = _getJVMFromJavaHome()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
        if os.path.exists(java_home+"/bin/javac") :
    TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
    ERROR:root:Importing native backends failed.
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
        embedded, remote = implementation.initialize(classpath, params)
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
        jvm = jpype.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
        return _linux.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
        jvm = _getJVMFromJavaHome()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
        if os.path.exists(java_home+"/bin/javac") :
    TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
    ERROR:root:Importing native backends failed.
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
        embedded, remote = implementation.initialize(classpath, params)
      File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
        jvm = jpype.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
        return _linux.getDefaultJVMPath()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
        jvm = _getJVMFromJavaHome()
      File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
        if os.path.exists(java_home+"/bin/javac") :
    TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

ile "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
    embedded, remote = implementation.initialize(classpath, params)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
    jvm = jpype.getDefaultJVMPath()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
    return _linux.getDefaultJVMPath()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
    jvm = _getJVMFromJavaHome()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
    if os.path.exists(java_home+"/bin/javac") :
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
ERROR:root:Importing native backends failed.
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
    embedded, remote = implementation.initialize(classpath, params)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
    jvm = jpype.getDefaultJVMPath()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
    return _linux.getDefaultJVMPath()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
    jvm = _getJVMFromJavaHome()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
    if os.path.exists(java_home+"/bin/javac") :
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
ERROR:root:Importing native backends failed.
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
    embedded, remote = implementation.initialize(classpath, params)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
    jvm = jpype.getDefaultJVMPath()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
    return _linux.getDefaultJVMPath()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
    jvm = _getJVMFromJavaHome()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
    if os.path.exists(java_home+"/bin/javac") :
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
ERROR:root:Importing native backends failed.
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/__init__.py", line 51, in initialize
    embedded, remote = implementation.initialize(classpath, params)
  File "/usr/local/lib/python2.7/dist-packages/Neo4j.py-0.1_SNAPSHOT-py2.7.egg/neo4j/_backend/reflection.py", line 44, in initialize
    jvm = jpype.getDefaultJVMPath()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_core.py", line 96, in getDefaultJVMPath
    return _linux.getDefaultJVMPath()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 36, in getDefaultJVMPath
    jvm = _getJVMFromJavaHome()
  File "/usr/local/lib/python2.7/dist-packages/jpype/_linux.py", line 55, in _getJVMFromJavaHome
    if os.path.exists(java_home+"/bin/javac") :
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

Answer 1

You can get more verbose information about why the backend couldn't be found by adding this to NEO4J_OPTIONS:

NEO4J_OPTIONS = {
    log: True,
}

The output from that logging will make it easier to diagnose the actual issue and suggest a fix.

Answer 2

your settings.py looks ok..

Do you have java SDK installed and JAVA_HOME environment variable set to your JDK? (java JRE is not enough)

From Neo4j.py docs:

In some situations the JPype compilation process might not link with the appropriate JNI headers, resulting in compilation errors. The first thing to note is that JPype needs the JNI headers from a JDK in order to build, it is not enough to only have a JRE installed when building JPype. If the JAVA_HOME environment variable is not set when building JPype the build script (setup.py) of JPype might have problems locating the appropriate JNI headers. If you are building JPype with sudo python setup.py install you might not inherit the JAVA_HOME environment variable into the sudo environment, an easy warkaround is to run python setup.py bdist before install.

Answer 3

I ran into the same problem. No matter what I did (on Debian) Python couldn't find the JAVA_HOME environmental variable. The easiest way to fix it, which I presume you can just add this somewhere in Django, is to add these lines -

java_home = os.getenv("JAVA_HOME")
if(java_home == None):
    os.environ["JAVA_HOME"] = "/usr/lib/jvm/java-6-openjdk"

where the path is the location of the JDK you want to use (it should have folder /bin after it with java and javac programs)

What I also tried was add the location to /etc/bash.bashrc. Which didn't work for me but might for you.

JAVA_HOME=/usr/lib/jvm/java-6-openjdk
export JAVA_HOME
PATH=$PATH:$JAVA_HOME/bin
export PATH

Anyway, that should get you started in the right direction. But now I have another related problem I'm stuck on with no answer for a week now :(