I have a Java class generated by Protocol Buffers called TextLine. When I instantiate the Java object with:
(def tb (-> (TextLine/newBuilder) (.setText "this is a text line") (.build)))
And then call:
(from-java tb)
I receive a StackOverflowError:
java.lang.StackOverflowError: null
at java.lang.Class.getMethods (Class.java:1614)
clojure.lang.Reflector.getMethods (Reflector.java:373)
clojure.lang.Reflector.invokeNoArgInstanceMember (Reflector.java:311)
clojure.java.data$add_getter_fn.invokeStatic (data.clj:38)
clojure.java.data$add_getter_fn.invoke (data.clj:37)
clojure.core.protocols$fn__6755.invokeStatic (protocols.clj:167)
clojure.core.protocols/fn (protocols.clj:124)
clojure.core.protocols$fn__6710$G__6705__6719.invoke (protocols.clj:19)
clojure.core.protocols$seq_reduce.invokeStatic (protocols.clj:31)
clojure.core.protocols$fn__6732.invokeStatic (protocols.clj:75)
clojure.core.protocols/fn (protocols.clj:75)
clojure.core.protocols$fn__6684$G__6679__6697.invoke (protocols.clj:13)
clojure.core$reduce.invokeStatic (core.clj:6545)
clojure.core$reduce.invoke (core.clj:6527)
clojure.java.data$eval554$fn__555.invoke (data.clj:135)
clojure.lang.MultiFn.invoke (MultiFn.java:229)
clojure.java.data$make_getter_fn$fn__501.invoke (data.clj:35)
clojure.java.data$eval554$fn__555$iter__556__560$fn__561.invoke (data.clj:136)
clojure.lang.LazySeq.sval (LazySeq.java:40)
clojure.lang.LazySeq.seq (LazySeq.java:49)
clojure.lang.Cons.next (Cons.java:39)
clojure.lang.RT.next (RT.java:688)
clojure.core$next__4341.invokeStatic (core.clj:64)
clojure.core.protocols$fn__6755.invokeStatic (protocols.clj:168)
clojure.core.protocols/fn (protocols.clj:124)
clojure.core.protocols$fn__6710$G__6705__6719.invoke (protocols.clj:19)
clojure.core.protocols$seq_reduce.invokeStatic (protocols.clj:31)
clojure.core.protocols$fn__6738.invokeStatic (protocols.clj:75)
clojure.core.protocols/fn (protocols.clj:75)
clojure.core.protocols$fn__6684$G__6679__6697.invoke (protocols.clj:13)
clojure.core$reduce.invokeStatic (core.clj:6545)
clojure.core$into.invokeStatic (core.clj:6610)
clojure.core$into.invoke (core.clj:6604)
clojure.java.data$eval554$fn__555.invoke (data.clj:136)
clojure.lang.MultiFn.invoke (MultiFn.java:229)
clojure.java.data$make_getter_fn$fn__501.invoke (data.clj:35)
clojure.java.data$eval554$fn__555$iter__556__560$fn__561.invoke (data.clj:136)
clojure.lang.LazySeq.sval (LazySeq.java:40)
clojure.lang.LazySeq.seq (LazySeq.java:49)
clojure.lang.Cons.next (Cons.java:39)
clojure.lang.RT.next (RT.java:688)
clojure.core$next__4341.invokeStatic (core.clj:64)
clojure.core.protocols$fn__6755.invokeStatic (protocols.clj:168)
clojure.core.protocols/fn (protocols.clj:124)
clojure.core.protocols$fn__6710$G__6705__6719.invoke (protocols.clj:19)
clojure.core.protocols$seq_reduce.invokeStatic (protocols.clj:31)
clojure.core.protocols$fn__6738.invokeStatic (protocols.clj:75)
clojure.core.protocols/fn (protocols.clj:75)
clojure.core.protocols$fn__6684$G__6679__6697.invoke (protocols.clj:13)
clojure.core$reduce.invokeStatic (core.clj:6545)
clojure.core$into.invokeStatic (core.clj:6610)
clojure.core$into.invoke (core.clj:6604)
clojure.java.data$eval554$fn__555.invoke (data.clj:136)
clojure.lang.MultiFn.invoke (MultiFn.java:229)
clojure.java.data$make_getter_fn$fn__501.invoke (data.clj:35)
clojure.java.data$eval554$fn__555$iter__556__560$fn__561.invoke (data.clj:136)
clojure.lang.LazySeq.sval (LazySeq.java:40)
clojure.lang.LazySeq.seq (LazySeq.java:49)
clojure.lang.Cons.next (Cons.java:39)
clojure.lang.RT.next (RT.java:688)
clojure.core$next__4341.invokeStatic (core.clj:64)
clojure.core.protocols$fn__6755.invokeStatic (protocols.clj:168)
clojure.core.protocols/fn (protocols.clj:124)
clojure.core.protocols$fn__6710$G__6705__6719.invoke (protocols.clj:19)
....
Any ideas on what could be causing this or the best way to troubleshoot it? I'd really like to interface with the Java object as a Clojure map.
I wouldn't recommend using clojure.data.java/from-java for much of anything. The idea that simple function can translate an arbitrary Java object into a reasonable Clojure map without any domain knowledge of the source object is wishful thinking.
I hadn't heard of it before today, but I went and looked at the source and as expected it is basically just an extension of clojure.core/bean, another hopeful attempt at an impossible problem. Specifically, it uses javabean introspection to try to guess what getters and setters represent meaningful fields. Now, However, like many Java classes that weren't designed to be used as beans, protobuf classes contain circular references, which means that recursively bean-ing them up is an infinite task, leading eventually to a stack overflow.
What to do instead? I would recommend just working with the generated Java protobuf classes through Java interop, or perhaps trying to find a good Clojure protobuf library. Don't try to convert the Java objects into idiomatic Clojure data.