Primitives and nested class problem with Class column type

[Ryszard-Trojnacki]

I'm unable to read (deserialize) Class type for nested class and primitives. Storing values to database works, but there is an error while retrieving/loading.

(This is not a big problem for me, because I just found this only in unit testing scenario)

In Java we can have nested classes:

public class ConfigDATest {

    // Nested class
    public static class TestConfig {
        public String name;
        public Long def;
        public BigDecimal value;
        public float f;
   }
}

When I tried to pass this class to Class type column:

public class DbConfig {
    @Column(name = "key", length = 128) @Id @Index(unique = true)
    private String key;

    @Column(name = "type")
    private Class<?> type;
}

then it is OK, to store it:

+------------------------------------------------------+
|type                                                  |
+------------------------------------------------------+
|java.lang.Integer                                     |
|test.ConfigDATest.TestConfig                          |
+------------------------------------------------------+

But when Ebean is loading this then there is an error:

Caused by: jakarta.persistence.PersistenceException: Error readSet on test.tables.DbConfig.type
	at io.ebeaninternal.server.deploy.BeanProperty.readSet(BeanProperty.java:527)
	at io.ebeaninternal.server.deploy.BeanProperty.readSet(BeanProperty.java:536)
	at io.ebeaninternal.server.query.SqlBeanLoad.load(SqlBeanLoad.java:63)
	... 21 more
Caused by: jakarta.persistence.PersistenceException: Unable to find Class test.ConfigDATest.TestConfig
	at io.ebeaninternal.server.type.ScalarTypeClass.parse(ScalarTypeClass.java:42)
	at io.ebeaninternal.server.type.ScalarTypeClass.convertFromDbString(ScalarTypeClass.java:24)
	at io.ebeaninternal.server.type.ScalarTypeClass.convertFromDbString(ScalarTypeClass.java:10)
	at io.ebean.core.type.ScalarTypeBaseVarchar.read(ScalarTypeBaseVarchar.java:63)
	at io.ebeaninternal.server.deploy.BeanProperty.readSet(BeanProperty.java:521)
	... 23 more
Caused by: java.lang.ClassNotFoundException: test.ConfigDATest.TestConfig
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:421)
	at java.base/java.lang.Class.forName(Class.java:412)
	at io.ebeaninternal.server.type.ScalarTypeClass.parse(ScalarTypeClass.java:40)
	... 27 more

The problem is with io.ebeaninternal.server.type.ScalarTypeClass it uses to serialize: Class#getCanonicalName and to load Class#forName.
This construction for nested class will not work:

        Class.forName(TestConfig.class.getName());   // Works
        Class.forName(TestConfig.class.getCanonicalName());  // Error

This will also not work for primitive types:

        Class.forName(int.class.getName());  // Error
        Class.forName(int.class.getCanonicalName());  // Error

Example code:

        var q=new DbConfig();
        q.setType(int.class);
        q.setKey("int_test");
        db.insert(q);

        var x=db.find(DbConfig.class, "int_test");

Here is error:

Caused by: jakarta.persistence.PersistenceException: Unable to find Class int
	at io.ebeaninternal.server.type.ScalarTypeClass.parse(ScalarTypeClass.java:42)
	at io.ebeaninternal.server.type.ScalarTypeClass.convertFromDbString(ScalarTypeClass.java:24)
	at io.ebeaninternal.server.type.ScalarTypeClass.convertFromDbString(ScalarTypeClass.java:10)
	at io.ebean.core.type.ScalarTypeBaseVarchar.read(ScalarTypeBaseVarchar.java:63)
	at io.ebeaninternal.server.deploy.BeanProperty.readSet(BeanProperty.java:521)

I can make PR with fix for this.

[rbygrave]

    @Column(name = "type")
    private Class<?> type;

The more I think about this the more I think it was a mistake for Ebean to support Class<?> from a security perspective. Instead Ebean should just use a String <-> Varchar and leave if up to the application to take that String and convert it to a class [and then that potential Class initialisation is owned by the application code and all security considerations around that are owned by the application code].

I think the correct thing for ebean to do here is effectively deprecate the mapping of @Column Class<?> and get people to migrate that into their application code.

[Ryszard-Trojnacki]

I think the correct thing for ebean to do here is effectively deprecate the mapping of @column Class<?> and get people to migrate that into their application code.

This makes a lot of sense.

Should I close the bug?

[rbygrave]

Should I close the bug?

Perhaps not yet. I'll determine a way to deprecate the Class<?> mapping and link that change to this issue.

[rbygrave]

Ebean will log a warning message when this mapping is used.