摘要：最近在研究圖計算相關技術，前一階段學了的知識，在學習的過程也對比一些其它的開源圖數(shù)據(jù)庫，如，還有一些通用框架。在的對比學習過程中，希望首先把已有的數(shù)據(jù)導入到新的數(shù)據(jù)庫中，還好官方提供了數(shù)據(jù)導入工具。

最近在研究圖計算相關技術，前一階段學了Neo4j的知識，在學習的過程也對比一些其它的開源圖數(shù)據(jù)庫，如OrientDB，還有一些通用框架TinkerPop。

在OrientDB的對比學習過程中，希望首先把已有的數(shù)據(jù)導入到新的數(shù)據(jù)庫中，還好OrientDB官方提供了Neo4j數(shù)據(jù)導入工具orientdb-neo4j-importer。然而一切皆有坑...

按照官方文檔進行數(shù)據(jù)導入，執(zhí)行命令：

sh orientdb-neo4j-importer-2.2.31/bin/orientdb-neo4j-importer.sh -neo4jdbdir ../graph.db/ -neo4jlibdir ../neo4jlib/

出現(xiàn)以下報錯：

Exception in thread "main" java.lang.NoClassDefFoundError: com/orientechnologies/orient/core/OConstants
    at com.orientechnologies.orient.neo4jimporter.ONeo4jImporterMain.main(ONeo4jImporterMain.java:15)
Caused by: java.lang.ClassNotFoundException: com.orientechnologies.orient.core.OConstants
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 1 more

嘗試把importer/lib/orientdb-neo4j-importer-2.2.31.jar拷貝到orientdb安裝目錄的lib文件夾下，再次執(zhí)行還是同樣的報錯。

查看源代碼也沒發(fā)現(xiàn)此處有問題，再通過sh打印詳細信息發(fā)現(xiàn)環(huán)境變量ORIENTDB_HOME設置有問題，執(zhí)行以下命令定義環(huán)境變量：

export ORIENTDB_HOME=/root/orientdb-community-importers-2.2.31

再次執(zhí)行命令，順利通過！

[root@datanode orientdb-community-importers-2.2.31]# sh -x orientdb-neo4j-importer-2.2.31/bin/orientdb-neo4j-importer.sh -neo4jdbdir ../graph.db/ -neo4jlibdir ../neo4jlib/
+ PRG=orientdb-neo4j-importer-2.2.31/bin/orientdb-neo4j-importer.sh
+ "[" -h orientdb-neo4j-importer-2.2.31/bin/orientdb-neo4j-importer.sh "]"
++ dirname orientdb-neo4j-importer-2.2.31/bin/orientdb-neo4j-importer.sh
+ PRGDIR=orientdb-neo4j-importer-2.2.31/bin
+ "[" -f /root/orientdb-community-importers-2.2.31/lib/orientdb-neo4j-importer-2.2.31.jar "]"
+ export ORIENTDB_HOME
+ "[" -f /usr/java/jdk1.8.0_91/bin/java "]"
+ JAVA=/usr/java/jdk1.8.0_91/bin/java
+ export JAVA
+ LOG_FILE=/root/orientdb-community-importers-2.2.31/config/orientdb-neo4j-importer-log.properties
+ JAVA_MAX_DIRECT=-XX:MaxDirectMemorySize=512g
+ JAVA_OPTS_SCRIPT="-XX:MaxDirectMemorySize=512g -Djava.util.logging.config.file=/root/orientdb-community-importers-2.2.31/config/orientdb-neo4j-importer-log.properties"
+ ARGS=
+ for var in ""$@""
+ ARGS=" -neo4jdbdir"
+ for var in ""$@""
+ ARGS=" -neo4jdbdir ../graph.db/"
+ for var in ""$@""
+ ARGS=" -neo4jdbdir ../graph.db/ -neo4jlibdir"
+ for var in ""$@""
+ ARGS=" -neo4jdbdir ../graph.db/ -neo4jlibdir ../neo4jlib/"
+ [[ 4 -gt 1 ]]
+ key=-neo4jdbdir
+ case $key in
+ shift
+ [[ 3 -gt 1 ]]
+ key=../graph.db/
+ case $key in
+ shift
+ [[ 2 -gt 1 ]]
+ key=-neo4jlibdir
+ case $key in
+ NEO4JLIB=../neo4jlib/
+ shift
+ shift
+ [[ 0 -gt 1 ]]
+ exec /usr/java/jdk1.8.0_91/bin/java -client -cp "../neo4jlib//*:/root/orientdb-community-importers-2.2.31/lib/*" -XX:MaxDirectMemorySize=512g -Djava.util.logging.config.file=/root/orientdb-community-importers-2.2.31/config/orientdb-neo4j-importer-log.properties com.orientechnologies.orient.neo4jimporter.ONeo4jImporterMain -neo4jdbdir ../graph.db/ -neo4jlibdir ../neo4jlib/

Neo4j to OrientDB Importer v.2.2.31 (build 285537d2767275f460df32c6a3be01bfff6a517c, branch 2.2.x) - Copyrights (c) 2016 OrientDB LTD

WARNING: "o" option not found. Defaulting to "false".

WARNING: "i" option not found. Defaulting to "false".

WARNING: "odbdir" option not found. Defaulting to "/root/databases/neo4j_import".

Please make sure that there are no running servers on:
  "../graph.db" (Neo4j)
and:
  "/root/databases/neo4j_import" (OrientDB)

Initializing Neo4j...Done

Initializing OrientDB...Done

Importing Neo4j database:
  "../graph.db"
into OrientDB database:
  "/root/databases/neo4j_import"

Getting all Nodes from Neo4j and creating corresponding Vertices in OrientDB...
  4 OrientDB Vertices have been created (100% done)
Done

Creating internal Indices on properties "Neo4jNodeID" & "Neo4jLabelList" on all OrientDB Vertices Classes...
  4 OrientDB Indices have been created (100% done)
Done

Getting all Relationships from Neo4j and creating corresponding Edges in OrientDB...
  2 OrientDB Edges have been created (100% done)
Done

Getting Constraints from Neo4j and creating corresponding ones in OrientDB...
  0 OrientDB UNIQUE Indices have been created
Done

Getting Indices from Neo4j and creating corresponding ones in OrientDB...
  0 OrientDB Indices have been created
Done

Import completed!

Shutting down OrientDB...Done
Shutting down Neo4j...Done

===============
Import Summary:
===============

- Found Neo4j Nodes                                                                           : 4
-- With at least one Label                                                                    :  4
--- With multiple Labels                                                                      :   0
-- Without Labels                                                                             :  0
- Imported OrientDB Vertices                                                                  : 4 (100%)

- Found Neo4j Relationships                                                                   : 2
- Imported OrientDB Edges                                                                     : 2 (100%)

- Found Neo4j Constraints                                                                     : 0
- Imported OrientDB Constraints (UNIQUE Indices created)                                      : 0
- NOT UNIQUE Indices created due to failure in creating UNIQUE Indices                        : 0

- Found Neo4j (non-constraint) Indices                                                        : 0
- Imported OrientDB Indices                                                                   : 0

- Additional internal Indices created                                                         : 4

- Total Import time:                                                                          : 6 seconds
-- Initialization time                                                                        :  5 seconds
-- Time to Import Nodes                                                                       :  0 seconds (35.4 nodes/sec)
-- Time to Import Relationships                                                               :  0 seconds (22.47 rels/sec)
-- Time to Import Constraints and Indices                                                     :  0 seconds (0 indices/sec)
-- Time to Create Internal Indices (on vertex properties "Neo4jNodeID" & "Neo4jLabelList")    :  1 seconds (7.01 indices/sec)

以為一切搞定，啟動OrientDB數(shù)據(jù)庫，并沒有看到新導入的數(shù)據(jù)庫... 再仔細查看發(fā)現(xiàn)沒有添加選項-odbdir（但是默認值應該是DB_HOME/databases/neo4j_import，不知道為何沒有生效...），數(shù)據(jù)庫導入到其它路徑下，拷貝過來后可以正常使用了。

（如圖，neo4j_import數(shù)據(jù)庫）