连接到 Neo4j 时出现以下错误：
Exception in thread "main" java.lang.RuntimeException: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.kernel.StoreLockerLifecycleAdapter@1798b372' was successfully initialized, but failed to start. Please see attached cause exception.
at org.neo4j.kernel.InternalAbstractGraphDatabase.run(InternalAbstractGraphDatabase.java:281)
at org.neo4j.kernel.EmbeddedGraphDatabase.<init>(EmbeddedGraphDatabase.java:106)
at org.neo4j.graphdb.factory.GraphDatabaseFactory$1.newDatabase(GraphDatabaseFactory.java:88)
at org.neo4j.graphdb.factory.GraphDatabaseBuilder.newGraphDatabase(GraphDatabaseBuilder.java:207)
at org.neo4j.graphdb.factory.GraphDatabaseFactory.newEmbeddedDatabase(GraphDatabaseFactory.java:69)
at com.neo4j.NeoStart.createDatabase(NeoStart.java:41)
at com.neo4j.NeoStart.main(NeoStart.java:26)
Caused by: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.kernel.StoreLockerLifecycleAdapter@1798b372' was successfully initialized, but failed to start. Please see attached cause exception.
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:497)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:104)
at org.neo4j.kernel.InternalAbstractGraphDatabase.run(InternalAbstractGraphDatabase.java:259)
... 6 more
Caused by: org.neo4j.kernel.StoreLockException: Could not create lock file
at org.neo4j.kernel.StoreLocker.checkLock(StoreLocker.java:74)
at org.neo4j.kernel.StoreLockerLifecycleAdapter.start(StoreLockerLifecycleAdapter.java:40)
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:491)
我已将 neo4j 安装为：apt-get install neo4j in ubuntu 12.04
我使用的 DB_PATH 如下： private static final String neo4j_DB_PATH=" /var/lib/neo4j/data/graph.db ";
请帮我解决这个问题...