Serializing/Deserializing simple maps should be better supported

[GoogleCodeExporter]

Attempting to simply serialize a map results in fairly useless output:

// dead simple map
Map<String, Object> m = new ArrayOrderedMap<String, Object>();
m.put("id", 123);
m.put("thing", "AZ");

// serialize (annoyingly requires the typetoken thing)
String encoded = gson.toJson(data, new TypeToken<Map<String, Object>>()
{}.getType());

encoded = {"id":{},"thing":{}}

It should have been:
encoded = {"id":123,"thing":"AZ"}

This should really be able to handle the simple example of a map of
primitive/simple objects much better. The same type of thing happens when
attempting to read back in the data.

With a more realistic example it is even worse because another map placed
inside the first map results in an exception like so:
com.google.gson.JsonParseException: The JsonSerializer
com.google.gson.DefaultTypeAdapters$MapTypeAdapter@b27bb5 failed to
serialized object {name=aaron, date=Mon Sep 15 11:58:33 BST 2008, num=456,
array=[Ljava.lang.String;@fe3238} given the type class java.lang.Object
    at
com.google.gson.JsonSerializerExceptionWrapper.serialize(JsonSerializerException
Wrapper.java:61)
    at
com.google.gson.JsonSerializationVisitor.visitUsingCustomHandler(JsonSerializati
onVisitor.java:177)
    at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:144)
    at
com.google.gson.JsonSerializationContextDefault.serialize(JsonSerializationConte
xtDefault.java:47)
    at
com.google.gson.DefaultTypeAdapters$MapTypeAdapter.serialize(DefaultTypeAdapters
.java:301)
    at
com.google.gson.DefaultTypeAdapters$MapTypeAdapter.serialize(DefaultTypeAdapters
.java:293)
    at
com.google.gson.JsonSerializerExceptionWrapper.serialize(JsonSerializerException
Wrapper.java:48)
    at
com.google.gson.JsonSerializationVisitor.visitUsingCustomHandler(JsonSerializati
onVisitor.java:177)
    at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:144)
    at
com.google.gson.JsonSerializationContextDefault.serialize(JsonSerializationConte
xtDefault.java:47)
    at com.google.gson.Gson.toJson(Gson.java:272)
    at com.google.gson.Gson.toJson(Gson.java:228)
    at
org.sakaiproject.entitybroker.impl.EntityEncodingManager.encodeData(EntityEncodi
ngManager.java:586)
    at
org.sakaiproject.entitybroker.impl.EntityEncodingManagerTest.testEncode(EntityEn
codingManagerTest.java:243)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.jav
a:25)
    at java.lang.reflect.Method.invoke(Method.java:585)
    at junit.framework.TestCase.runTest(TestCase.java:154)
    at junit.framework.TestCase.runBare(TestCase.java:127)
    at junit.framework.TestResult$1.protect(TestResult.java:106)
    at junit.framework.TestResult.runProtected(TestResult.java:124)
    at junit.framework.TestResult.run(TestResult.java:109)
    at junit.framework.TestCase.run(TestCase.java:118)
    at junit.framework.TestSuite.runTest(TestSuite.java:208)
    at junit.framework.TestSuite.run(TestSuite.java:203)
    at
org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestR
eference.java:130)
    at
org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner
.java:460)
    at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner
.java:673)
    at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java
:386)
    at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.jav
a:196)
Caused by: java.lang.IllegalArgumentException: Map objects need to be
parameterized unless you use a custom serializer. Use the
com.google.gson.reflect.TypeToken to extract the ParameterizedType.
    at com.google.gson.TypeInfoMap.<init>(TypeInfoMap.java:34)
    at
com.google.gson.DefaultTypeAdapters$MapTypeAdapter.serialize(DefaultTypeAdapters
.java:298)
    at
com.google.gson.DefaultTypeAdapters$MapTypeAdapter.serialize(DefaultTypeAdapters
.java:293)
    at
com.google.gson.JsonSerializerExceptionWrapper.serialize(JsonSerializerException
Wrapper.java:48)
    ... 31 more

Original issue reported on code.google.com by azeckoski on 15 Sep 2008 at 11:00