Problem with `JavaType.toString()` for recursive (self-referential) types

[voidmain]

I'm getting a StackOverflowError when I try to use this class with Jackson:

public class DataDefinition extends HashMap<String, DataDefinition> {
  public DataDefinition definition;
  public DataDefinition elements;
  public String regex;
  public boolean required;
  public String type;
}

Here's a snippet of the stack trace I get:

    at com.fasterxml.jackson.databind.type.ResolvedRecursiveType.toString(ResolvedRecursiveType.java:90)
    at java.lang.String.valueOf(String.java:2994)
    at java.lang.StringBuilder.append(StringBuilder.java:131)
    at com.fasterxml.jackson.databind.type.MapType.toString(MapType.java:161)
    at java.lang.String.valueOf(String.java:2994)
    at java.lang.StringBuilder.append(StringBuilder.java:131)
    at com.fasterxml.jackson.databind.type.ResolvedRecursiveType.toString(ResolvedRecursiveType.java:90)
    at java.lang.String.valueOf(String.java:2994)

I did some debugging and found that this looks like the location where the stack track starts:

    public StdValueInstantiator(DeserializationConfig config, JavaType valueType) {
        _valueTypeDesc = (valueType == null) ? "UNKNOWN TYPE" : valueType.toString();
        _valueClass = (valueType == null) ? Object.class : valueType.getRawClass();
    }

It's line 87 in StdValueInstantiator. That looks like it is calling toString() on the on the type and then it goes into an infinite recursion state. I'm not sure why the toString() call is necessary, but it seems like all of this is for debugging and errors and pre-calculating the string is preventing Jackson from working at all even if there isn't an error.

WORK-AROUND: In case anyone looks at this issue and needs a work around, you can use the @JsonAnySetter to fix this issue. Here's the code:

public class DataDefinition {
  public DataDefinition definition;
  public DataDefinition elements;
  @JsonAnySetter
  public Map<String, DataDefinition> properties = new HashMap<>();
  public String regex;
  public boolean required;
  public String type;
}

I also think that this can likely be fixed with code like this:

com.fasterxml.jackson.databind.type.MapType.java#toString()

    public String toString()
    {
        if ((_keyType instance ResolvedRecursiveType && ((ResolvedRecursiveType) _keyType).getSelfReferencedType() == this) || (_valueType instance ResolvedRecursiveType && ((ResolvedRecursiveType) _valueType).getSelfReferencedType() == this)) {
            return "[map type; class "+_class.getName()+", "+_keyType+" -> self]";
        }
        return "[map type; class "+_class.getName()+", "+_keyType+" -> "+_valueType+"]";
    }

[cowtowncoder]

Hmmh. This is tricky because it is truly recursive definition, and there is no clean way to keep track of reference track during toString(). Obviously code should not fail that way, so need to figure out a better way to make this work.
Plus in general toString() can't fail that way either. Just need to think of the cleanest way to resolve the problem.

[cowtowncoder]

Thank you again -- I was able to fix it relatively easily since this affects self-referential ResolvedRecursiveType instances. Fix is in for 2.7.6 and 2.8.1 (since these are open branches).

[cowtowncoder]

Also: for what that is worth, test fails on 2.6, but for other reasons; recursive type resolution itself fails.
Type resolution was rewritten in 2.7 to address this case (amongst others), so there is no way to backport fix there, even if branch was open.

[newkek]

Hello, I am using jackson-databind 2.8.8, and have a class with a similar definition (extending a Map, where the values are are of the type of the same class). It seems like I am still facing this exact recursion issue.

Here's the definition of the class:

public class Tree<T> extends HashMap<T, Tree<T>> implements Serializable {
....
}

Now, when executing the following code:

        ObjectMapper om = new ObjectMapper();
        final TypeResolverBuilder<?> typer = new StdTypeResolverBuilder()
                .init(JsonTypeInfo.Id.CLASS, null)
                .inclusion(JsonTypeInfo.As.PROPERTY)
                .typeProperty(GraphSONTokens.CLASS);
        om.setDefaultTyping(typer);

        String res = om.writeValueAsString(t);
        Object tRead = om.readValue(res, Tree.class);

        System.out.println("tRead = " + tRead);

When calling readValue() the mapper throws a StackOverflowException , here's the stacktrace:

java.lang.StackOverflowError
	at org.apache.tinkerpop.shaded.jackson.databind.type.MapLikeType.equals(MapLikeType.java:305)
	at org.apache.tinkerpop.shaded.jackson.databind.type.ResolvedRecursiveType.equals(ResolvedRecursiveType.java:110)
	at org.apache.tinkerpop.shaded.jackson.databind.type.MapLikeType.equals(MapLikeType.java:305)
	at org.apache.tinkerpop.shaded.jackson.databind.type.ResolvedRecursiveType.equals(ResolvedRecursiveType.java:110)
	at org.apache.tinkerpop.shaded.jackson.databind.type.MapLikeType.equals(MapLikeType.java:305)
	at org.apache.tinkerpop.shaded.jackson.databind.type.ResolvedRecursiveType.equals(ResolvedRecursiveType.java:110)
	at org.apache.tinkerpop.shaded.jackson.databind.type.MapLikeType.equals(MapLikeType.java:305)
	at org.apache.tinkerpop.shaded.jackson.databind.type.ResolvedRecursiveType.equals(ResolvedRecursiveType.java:110)
	at org.apache.tinkerpop.shaded.jackson.databind.type.MapLikeType.equals(MapLikeType.java:305)
[...]

Looking briefly into the code, it seems like because of the recursive definition of the class, the equals call in MapLikeType may never get out of this loop. Any idea?

[cowtowncoder]

@newkek Could you please file a new issue, copying information you provided? I need a reproduction and see if and how to prevent infinite recursion. It is possible this is regression due to other changes/fixes needed to support usage of self-recursive type references.

[newkek]

Thanks - will do right away.

[newkek]

New issue: #1658.
Thanks.

@ALL - How to solve this issue ? Does any knows the solution ?