每当我更改代码中的某些内容时，java.lang.ClassNotFoundException（Neo4j OGM+；Play！）

我从两周前就成功地使用了Neo4J OGM+Play框架，但现在它已经不起作用了。每当我更改代码中的某些内容时，无论是在NodeEntity类还是在任何其他类中，当我尝试使用org.neo4j.ogm.session.session中的find方法从数据库中获取某些内容时，都会导致java.lang.ClassNotFoundException。只有清除数据库并重新填充，我才能插入并获取节点实体

Java版本：1.8
Scala版本：2.11.7
Sbt版本：2.6.3

构建.sbt：

libraryDependencies += "org.neo4j" % "neo4j-ogm-core" % "3.0.0-RC1"
libraryDependencies += "org.neo4j" % "neo4j-ogm-bolt-driver" % "3.0.0-RC1"

Neo4JSessionFactory.java

public class Neo4jSessionFactory {

    private Config config;

    @Inject
    private Neo4jSessionFactory(Config config) {
        this.config = config;
    }


    public Session getNeo4jSession() {
        String uri = config.getString("ogm.db.uri");
        String username = config.getString("ogm.db.username");
        String password = config.getString("ogm.db.password");
        List<String> modelList = config.getStringList("ogm.db.models");

        String[] models = modelList.toArray(new String[modelList.size()]);

        Configuration configuration = new Configuration.Builder()
                .uri(uri)
                .credentials(username, password)
                .build();
        return new SessionFactory(configuration, models).openSession();
    }
}

ogm{
   db{
     uri = "bolt://XXX.de:7687"
     username = "XXX"
     password = "XXX"
     models = ["neo4j.nodes", "neo4j.relationships", "neo4j.entities"]
   }
}

@NodeEntity(label = "UserNode")
public class UserNode extends AbstractNode {

    @JsonProperty("username")
    private String username;

    @JsonProperty("firstname")
    private String firstname;

    @JsonProperty("lastname")
    private String lastname;

    @JsonProperty("email")
    private String email;

    @JsonProperty("password")
    private String password;

    @JsonProperty("picture")
    private String picture;

    @Relationship(type = Friendship.TYPE)
    @JsonProperty("friendships")
    private Set<Friendship> friendships = new HashSet<>();

    @Relationship(type = Posted.TYPE)
    @JsonProperty("postings")
    private Set<Posted> postings = new HashSet<>();

    @Relationship(type = Pinned.TYPE, direction = Relationship.INCOMING)
    @JsonProperty("pinnings")
    private Set<Pinned> pinnings = new HashSet<>();


    public UserNode() {
    }
}

public Result all(){
    return toJsonResult(service.findAll());  <-- (AbstractCRUDController.java:19)
}

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[MappingException: Error mapping GraphModel to instance of neo4j.nodes.UserNode]]
at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:255)
at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:180)
at play.core.server.AkkaHttpServer$$anonfun$13$$anonfun$apply$1.applyOrElse(AkkaHttpServer.scala:251)
at play.core.server.AkkaHttpServer$$anonfun$13$$anonfun$apply$1.applyOrElse(AkkaHttpServer.scala:250)
at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:344)
at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:343)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at play.api.libs.streams.Execution$trampoline$.execute(Execution.scala:70)
at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:40)
at scala.concurrent.impl.Promise$DefaultPromise.scala$concurrent$impl$Promise$DefaultPromise$$dispatchOrAddCallback(Promise.scala:280)
Caused by: org.neo4j.ogm.exception.MappingException: Error mapping GraphModel to instance of neo4j.nodes.UserNode
at org.neo4j.ogm.context.GraphEntityMapper.mapEntities(GraphEntityMapper.java:168)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:124)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:89)
at org.neo4j.ogm.session.delegates.LoadByTypeDelegate.loadAll(LoadByTypeDelegate.java:65)
at org.neo4j.ogm.session.delegates.LoadByTypeDelegate.loadAll(LoadByTypeDelegate.java:99)
at org.neo4j.ogm.session.Neo4jSession.loadAll(Neo4jSession.java:167)
at neo4j.services.AbstractService.findAll(AbstractService.java:27)
at controllers.AbstractCRUDController.all(AbstractCRUDController.java:19)
at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$2$$anonfun$apply$2.apply(Routes.scala:364)
at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$2$$anonfun$apply$2.apply(Routes.scala:364)
Caused by: org.neo4j.ogm.exception.MappingException: Unable to load class with FQN: neo4j.nodes.UserNode
at org.neo4j.ogm.metadata.reflect.EntityFactory.instantiateObjectFromTaxa(EntityFactory.java:109)
at org.neo4j.ogm.metadata.reflect.EntityFactory.newObject(EntityFactory.java:58)
at org.neo4j.ogm.context.GraphEntityMapper.mapNodes(GraphEntityMapper.java:179)
at org.neo4j.ogm.context.GraphEntityMapper.mapEntities(GraphEntityMapper.java:165)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:124)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:89)
at org.neo4j.ogm.session.delegates.LoadByTypeDelegate.loadAll(LoadByTypeDelegate.java:65)
at org.neo4j.ogm.session.delegates.LoadByTypeDelegate.loadAll(LoadByTypeDelegate.java:99)
at org.neo4j.ogm.session.Neo4jSession.loadAll(Neo4jSession.java:167)
at neo4j.services.AbstractService.findAll(AbstractService.java:27)
Caused by: java.lang.ClassNotFoundException: neo4j.nodes.UserNode
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 org.neo4j.ogm.metadata.reflect.EntityFactory.instantiateObjectFromTaxa(EntityFactory.java:106)
at org.neo4j.ogm.metadata.reflect.EntityFactory.newObject(EntityFactory.java:58)
at org.neo4j.ogm.context.GraphEntityMapper.mapNodes(GraphEntityMapper.java:179)
at org.neo4j.ogm.context.GraphEntityMapper.mapEntities(GraphEntityMapper.java:165)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:124)

UserNode.java

public class Neo4jSessionFactory {

    private Config config;

    @Inject
    private Neo4jSessionFactory(Config config) {
        this.config = config;
    }


    public Session getNeo4jSession() {
        String uri = config.getString("ogm.db.uri");
        String username = config.getString("ogm.db.username");
        String password = config.getString("ogm.db.password");
        List<String> modelList = config.getStringList("ogm.db.models");

        String[] models = modelList.toArray(new String[modelList.size()]);

        Configuration configuration = new Configuration.Builder()
                .uri(uri)
                .credentials(username, password)
                .build();
        return new SessionFactory(configuration, models).openSession();
    }
}

ogm{
   db{
     uri = "bolt://XXX.de:7687"
     username = "XXX"
     password = "XXX"
     models = ["neo4j.nodes", "neo4j.relationships", "neo4j.entities"]
   }
}

@NodeEntity(label = "UserNode")
public class UserNode extends AbstractNode {

    @JsonProperty("username")
    private String username;

    @JsonProperty("firstname")
    private String firstname;

    @JsonProperty("lastname")
    private String lastname;

    @JsonProperty("email")
    private String email;

    @JsonProperty("password")
    private String password;

    @JsonProperty("picture")
    private String picture;

    @Relationship(type = Friendship.TYPE)
    @JsonProperty("friendships")
    private Set<Friendship> friendships = new HashSet<>();

    @Relationship(type = Posted.TYPE)
    @JsonProperty("postings")
    private Set<Posted> postings = new HashSet<>();

    @Relationship(type = Pinned.TYPE, direction = Relationship.INCOMING)
    @JsonProperty("pinnings")
    private Set<Pinned> pinnings = new HashSet<>();


    public UserNode() {
    }
}

public Result all(){
    return toJsonResult(service.findAll());  <-- (AbstractCRUDController.java:19)
}

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[MappingException: Error mapping GraphModel to instance of neo4j.nodes.UserNode]]
at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:255)
at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:180)
at play.core.server.AkkaHttpServer$$anonfun$13$$anonfun$apply$1.applyOrElse(AkkaHttpServer.scala:251)
at play.core.server.AkkaHttpServer$$anonfun$13$$anonfun$apply$1.applyOrElse(AkkaHttpServer.scala:250)
at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:344)
at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:343)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at play.api.libs.streams.Execution$trampoline$.execute(Execution.scala:70)
at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:40)
at scala.concurrent.impl.Promise$DefaultPromise.scala$concurrent$impl$Promise$DefaultPromise$$dispatchOrAddCallback(Promise.scala:280)
Caused by: org.neo4j.ogm.exception.MappingException: Error mapping GraphModel to instance of neo4j.nodes.UserNode
at org.neo4j.ogm.context.GraphEntityMapper.mapEntities(GraphEntityMapper.java:168)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:124)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:89)
at org.neo4j.ogm.session.delegates.LoadByTypeDelegate.loadAll(LoadByTypeDelegate.java:65)
at org.neo4j.ogm.session.delegates.LoadByTypeDelegate.loadAll(LoadByTypeDelegate.java:99)
at org.neo4j.ogm.session.Neo4jSession.loadAll(Neo4jSession.java:167)
at neo4j.services.AbstractService.findAll(AbstractService.java:27)
at controllers.AbstractCRUDController.all(AbstractCRUDController.java:19)
at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$2$$anonfun$apply$2.apply(Routes.scala:364)
at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$2$$anonfun$apply$2.apply(Routes.scala:364)
Caused by: org.neo4j.ogm.exception.MappingException: Unable to load class with FQN: neo4j.nodes.UserNode
at org.neo4j.ogm.metadata.reflect.EntityFactory.instantiateObjectFromTaxa(EntityFactory.java:109)
at org.neo4j.ogm.metadata.reflect.EntityFactory.newObject(EntityFactory.java:58)
at org.neo4j.ogm.context.GraphEntityMapper.mapNodes(GraphEntityMapper.java:179)
at org.neo4j.ogm.context.GraphEntityMapper.mapEntities(GraphEntityMapper.java:165)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:124)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:89)
at org.neo4j.ogm.session.delegates.LoadByTypeDelegate.loadAll(LoadByTypeDelegate.java:65)
at org.neo4j.ogm.session.delegates.LoadByTypeDelegate.loadAll(LoadByTypeDelegate.java:99)
at org.neo4j.ogm.session.Neo4jSession.loadAll(Neo4jSession.java:167)
at neo4j.services.AbstractService.findAll(AbstractService.java:27)
Caused by: java.lang.ClassNotFoundException: neo4j.nodes.UserNode
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 org.neo4j.ogm.metadata.reflect.EntityFactory.instantiateObjectFromTaxa(EntityFactory.java:106)
at org.neo4j.ogm.metadata.reflect.EntityFactory.newObject(EntityFactory.java:58)
at org.neo4j.ogm.context.GraphEntityMapper.mapNodes(GraphEntityMapper.java:179)
at org.neo4j.ogm.context.GraphEntityMapper.mapEntities(GraphEntityMapper.java:165)
at org.neo4j.ogm.context.GraphEntityMapper.map(GraphEntityMapper.java:124)

---

有人能告诉我我是要发疯了还是还需要保存吗？

我试过你的代码，发现这个错误只在GET请求时发生。

---

我在尝试使用POST请求插入时发现了这一点。在这种情况下，“find”-方法已经找到了适当的类，但是后续的GET请求没有找到。但我不明白为什么GET请求不起作用。可能标题与POST请求不同？放弃get以获取资源也不是一个永久的解决方案。

尝试激活

org.neo4j.ogm

包上的调试日志。这将为您指出解决方案。作为旁注：在您的案例中，会话应该是短期对象。您应该插入并保持

会话工厂

，而不是会话。然后在您的服务层中，当您访问数据库时，获得一个短期会话