Question

I’m using MyBatis with playframework and everything works nicely except:

When I’ve attempted to use the default cache built in MyBatis (<cache/> tag in xml mapper files), upon retrieving a cached select statement I get this stacktrace.

If I run the same statements in a unit test (or another application without playframework involved) everything works fine.

So, my guess it has something to do the way playframework loads/compiles the classes some sort of classloader issue.

The directory layout of my project looks something like this (relevant bits):

app
  controllers
  data // xml mapping files and java interfaces for ibatis
       // & a class that returns a SqlSessionFactory
    domain // Pojos for SQL results (e.g. User.java)
  models
  views
lib // here is myibatis jar file
(...) // the rest of the standard play framework project

The model method that throws the exception is this:

  public static UserAuthentication findAuthenticatonIdentity(UserId userId){
    SqlSessionFactory sessionFactory = IbatisSessionFactory.getSqlMapper();
    SqlSession session = sessionFactory.openSession();
    AuthMapper authMapper = session.getMapper(AuthMapper.class);

    UserAuthentication ua = authMapper.selectByUserId(userId); // line 162
    session.close();
    return ua;
  }

And UserAuthentication implements Serializable!

And here is the stacktrace:

Execution exception (In /app/models/UserModel.java around line 162)
PersistenceException occured : 
 ### Error querying database.  Cause: org.apache.ibatis.cache.CacheException: Error deserializing object.  Cause: java.lang.ClassNotFoundException: data.domain.UserAuthentication
 ### Cause: org.apache.ibatis.cache.CacheException: Error deserializing object.  Cause: java.lang.ClassNotFoundException: data.domain.UserAuthentication

play.exceptions.JavaExecutionException: 
### Error querying database.  Cause: org.apache.ibatis.cache.CacheException: Error deserializing object.  Cause: java.lang.ClassNotFoundException: data.domain.UserAuthentication
### Cause: org.apache.ibatis.cache.CacheException: Error deserializing object.  Cause: java.lang.ClassNotFoundException: data.domain.UserAuthentication
    at play.mvc.ActionInvoker.invoke(ActionInvoker.java:231)
    at Invocation.HTTP Request(Play!)
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: org.apache.ibatis.cache.CacheException: Error deserializing object.  Cause: java.lang.ClassNotFoundException: data.domain.UserAuthentication
### Cause: org.apache.ibatis.cache.CacheException: Error deserializing object.  Cause: java.lang.ClassNotFoundException: data.domain.UserAuthentication
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:102)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:94)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:58)
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:90)
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:40)
    at $Proxy8.selectByUserId(Unknown Source)
    at models.UserModel.findAuthenticatonIdentity(UserModel.java:162)
    at controllers.securesocial.MySecureSocial.checkAccess(MySecureSocial.java:97)
    at play.mvc.ActionInvoker.invoke(ActionInvoker.java:504)
    at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:478)
    at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:473)
    at play.mvc.ActionInvoker.handleBefores(ActionInvoker.java:322)
    at play.mvc.ActionInvoker.invoke(ActionInvoker.java:142)
    ... 1 more
Caused by: org.apache.ibatis.cache.CacheException: Error deserializing object.  Cause: java.lang.ClassNotFoundException: data.domain.UserAuthentication
    at org.apache.ibatis.cache.decorators.SerializedCache.deserialize(SerializedCache.java:94)
    at org.apache.ibatis.cache.decorators.SerializedCache.getObject(SerializedCache.java:50)
    at org.apache.ibatis.cache.decorators.LoggingCache.getObject(LoggingCache.java:50)
    at org.apache.ibatis.cache.decorators.SynchronizedCache.getObject(SynchronizedCache.java:55)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:72)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:100)
    ... 13 more
Caused by: java.lang.ClassNotFoundException: data.domain.UserAuthentication
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:247)
    at java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:603)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1574)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1495)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1731)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1328)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:350)
    at java.util.ArrayList.readObject(ArrayList.java:593)
    at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974)
    at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1848)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1752)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1328)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:350)
    at org.apache.ibatis.cache.decorators.SerializedCache.deserialize(SerializedCache.java:91)
    ... 18 more

UserAuthentication.java

public class UserAuthentication implements Serializable {

  private int id;
  private String authId;
  private String secret;
  private String token; // Oauth1 token
  private String accessToken; // Oauth2 request token
  private String displayName;
  private String authMethod;
  private String provider;
  private String email;
  private String avatarUrl;
  private Date lastAccess;
  private String password;
  private boolean emailVerified;
  private int userId;
  private String activationUuid;
  private Date activationExpiry;

  // + getters & setters
}

UserId.java

public class UserId implements java.io.Serializable {
    /**
     * The id the user has in a external service.
     */
    public String id;

    /**
     * The provider this user belongs to.
     */
    public ProviderType provider; // simple enum
}

Answer 1

Sorry, I think I was wrong – this is not a name collision but rather a classloader problem.

Play uses a dynamic classloading mechanism to detect changes to the source code and enhance methods through bytecode injection. http://groups.google.com/group/play-framework/browse_frm/thread/359736394ae27902/98445c557833036c

I think the problem may be that MyBatis is using the regular class loader – so can’t find the classes that are loaded via Play’s mechanism. When you put the source into the Play directory, MyBatis is then using the Play classloader.

Here are some options:

1) Compile your domain objects into a JAR file. Include that jar in your project: http://groups.google.com/group/play-framework/browse_thread/thread/b54e4e25ae49161b

2) Force MyBatis to use the Play classloader – somewhere before any mybatis calls

Thread.currentThread().setContextClassLoader(Play.classloader); 

http://groups.google.com/group/play-framework/browse_thread/thread/f4789ee5c20609af/d1412a914dc06851?#d1412a914dc06851

Still seems like a hack, but perhaps it keeps your application source size down.

3) Ensure your classes are loaded before the calls to MyBatis. So, in this case.

Class.forName("data.domain.UserAuthentication");
Class.forName("data.domain.UserId");

Which seems far worse of a hack.

I hope one of those options works for you.