除了 MySQL 数据库之外，我还想从我的 Play Framework 应用程序访问 Neo4j 数据库。MySQL 访问工作正常。为了准备通过 Bolt 访问 Neo4j 的代码，我有：
在项目 build.sbt 中添加了对 Driver 的引用：
libraryDependencies ++= Seq(
jdbc,
cache,
ws,
specs2 % Test,
"org.mindrot" % "jbcrypt" % "0.3m",
"mysql" % "mysql-connector-java" % "5.1.38",
"org.neo4j" % "neo4j-bolt" % "3.0.1"
)
我重新启动了 activator 并看到它显然解决/检索了我现在可以在 ~/.ivy2/... 中找到的依赖项
我还在 application.conf 中放置了对我的数据库的引用，如以下片段所示：
db.default = {
driver: com.mysql.jdbc.Driver
url: "jdbc:mysql://127.0.0.1/borg"
username: "borg"
password: "XXXXX"
}
# Bolt port # defaults to 7687 I hope
db.neo4j = {
driver: org.neo4j.jdbc.Driver
url: "jdbc:neo4j:bolt://neo.myco.com"
username: "neo4j"
password: "XX"
}
我还没有编写任何 Scala 代码来尝试访问数据库。简单地将此规范添加到 application.conf 会导致应用程序在从站点检索任何内容时失败，并带有以下堆栈跟踪中所示的消息。我注意到一条关于“找不到驱动程序 [org.neo4j.jdbc.Driver}]”的消息，奇怪的是在一个特殊的位置有一个右括号。我想知道这是否是一个红鲱鱼。有什么见解或经验吗？
CreationException: Unable to create injector, see the following errors:
1) Error in custom provider, Configuration error: Configuration error[Cannot connect to database [neo4j]]
while locating play.api.db.DBApiProvider
while locating play.api.db.DBApi for field
at play.api.db.NamedDatabaseProvider.dbApi(DBModule.scala:80)
while locating play.api.db.NamedDatabaseProvider
at com.google.inject.util.Providers$GuicifiedProviderWithDependencies.initialize(Providers.java:149)
at play.api.db.DBModule$$anonfun$namedDatabaseBindings$1.apply(DBModule.scala:34):
Binding(interface play.api.db.Database qualified with QualifierInstance(@play.db.NamedDatabase(value=default)) to ProviderTarget(play.api.db.NamedDatabaseProvider@746bce08)) (via modules: com.google.inject.util.Modules$OverrideModule -> play.api.inject.guice.GuiceableModuleConversions$$anon$1)
Caused by: Configuration error: Configuration error[Cannot connect to database [neo4j]]
at play.api.Configuration$.configError(Configuration.scala:178)
at play.api.Configuration.reportError(Configuration.scala:829)
at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:48)
at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:42)
at scala.collection.immutable.List.foreach(List.scala:381)
at play.api.db.DefaultDBApi.connect(DefaultDBApi.scala:42)
at play.api.db.DBApiProvider.get$lzycompute(DBModule.scala:72)
at play.api.db.DBApiProvider.get(DBModule.scala:62)
at play.api.db.DBApiProvider.get(DBModule.scala:58)
at com.google.inject.internal.ProviderInternalFactory.provision(ProviderInternalFactory.java:81)
at com.google.inject.internal.BoundProviderFactory.provision(BoundProviderFactory.java:72)
at com.google.inject.internal.ProviderInternalFactory.circularGet(ProviderInternalFactory.java:61)
at com.google.inject.internal.BoundProviderFactory.get(BoundProviderFactory.java:62)
at com.google.inject.internal.SingleFieldInjector.inject(SingleFieldInjector.java:54)
at com.google.inject.internal.MembersInjectorImpl.injectMembers(MembersInjectorImpl.java:132)
at com.google.inject.internal.MembersInjectorImpl$1.call(MembersInjectorImpl.java:93)
at com.google.inject.internal.MembersInjectorImpl$1.call(MembersInjectorImpl.java:80)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1103)
at com.google.inject.internal.MembersInjectorImpl.injectAndNotify(MembersInjectorImpl.java:80)
at com.google.inject.internal.MembersInjectorImpl.injectMembers(MembersInjectorImpl.java:62)
at com.google.inject.internal.InjectorImpl.injectMembers(InjectorImpl.java:984)
at com.google.inject.util.Providers$GuicifiedProviderWithDependencies.initialize(Providers.java:149)
at com.google.inject.util.Providers$GuicifiedProviderWithDependencies$$FastClassByGuice$$2a7177aa.invoke(<generated>)
at com.google.inject.internal.cglib.reflect.$FastMethod.invoke(FastMethod.java:53)
at com.google.inject.internal.SingleMethodInjector$1.invoke(SingleMethodInjector.java:57)
at com.google.inject.internal.SingleMethodInjector.inject(SingleMethodInjector.java:91)
at com.google.inject.internal.MembersInjectorImpl.injectMembers(MembersInjectorImpl.java:132)
at com.google.inject.internal.MembersInjectorImpl$1.call(MembersInjectorImpl.java:93)
at com.google.inject.internal.MembersInjectorImpl$1.call(MembersInjectorImpl.java:80)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1092)
at com.google.inject.internal.MembersInjectorImpl.injectAndNotify(MembersInjectorImpl.java:80)
at com.google.inject.internal.Initializer$InjectableReference.get(Initializer.java:174)
at com.google.inject.internal.Initializer.injectAll(Initializer.java:108)
at com.google.inject.internal.InternalInjectorCreator.injectDynamically(InternalInjectorCreator.java:174)
at com.google.inject.internal.InternalInjectorCreator.build(InternalInjectorCreator.java:110)
at com.google.inject.Guice.createInjector(Guice.java:96)
at com.google.inject.Guice.createInjector(Guice.java:73)
at com.google.inject.Guice.createInjector(Guice.java:62)
at play.api.inject.guice.GuiceBuilder.injector(GuiceInjectorBuilder.scala:126)
at play.api.inject.guice.GuiceApplicationBuilder.build(GuiceApplicationBuilder.scala:93)
at play.api.inject.guice.GuiceApplicationLoader.load(GuiceApplicationLoader.scala:21)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1$$anonfun$2.apply(DevServerStart.scala:153)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1$$anonfun$2.apply(DevServerStart.scala:150)
at play.utils.Threads$.withContextClassLoader(Threads.scala:21)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(DevServerStart.scala:150)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(DevServerStart.scala:121)
at scala.Option.map(Option.scala:146)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1.apply(DevServerStart.scala:121)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1.apply(DevServerStart.scala:119)
at scala.util.Success.flatMap(Try.scala:231)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1.apply(DevServerStart.scala:119)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1.apply(DevServerStart.scala:111)
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1689)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
Caused by: Configuration error: Configuration error[Driver not found: [org.neo4j.jdbc.Driver}]]
at play.api.Configuration$.configError(Configuration.scala:178)
at play.api.PlayConfig.reportError(Configuration.scala:1048)
at play.api.db.DefaultDatabase$$anonfun$driver$1.apply(Databases.scala:115)
at play.api.db.DefaultDatabase$$anonfun$driver$1.apply(Databases.scala:109)
at scala.Option.map(Option.scala:146)
at play.api.db.DefaultDatabase.driver$lzycompute(Databases.scala:109)
at play.api.db.DefaultDatabase.driver(Databases.scala:108)
at play.api.db.DefaultDatabase.dataSource$lzycompute(Databases.scala:123)
at play.api.db.DefaultDatabase.dataSource(Databases.scala:122)
at play.api.db.DefaultDatabase.getConnection(Databases.scala:143)
at play.api.db.DefaultDatabase.getConnection(Databases.scala:139)
at play.api.db.DefaultDBApi$$anonfun$connect$1.apply(DefaultDBApi.scala:44)
... 56 more
Caused by: @70ombh24b: Cannot load Driver
at play.utils.Reflect$.createInstance(Reflect.scala:137)
at play.api.db.DefaultDatabase$$anonfun$driver$1.apply(Databases.scala:111)
... 65 more
Caused by: java.lang.ClassNotFoundException: org.neo4j.jdbc.Driver
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at play.utils.Reflect$.getClass(Reflect.scala:142)
at play.utils.Reflect$.createInstance(Reflect.scala:131)
... 66 more