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From erj2code <p...@tetraconcepts.com>
Subject How do I marshall nested key,value pairs into JSON with Camel and Jackson library?
Date Tue, 15 Oct 2013 19:47:52 GMT
I have a Java project that currently returns a map to Camel without any
nested key,value pairs, and the Jackson library marshalls it just fine into
JSON using the Jackson library.

For example if I put the following two key,values into a demoMap:

    Map<String,String> demoMap = new TreeMap<String,String>
    demoMap.put("key1","5");
    demoMap.put("key2","10");

I get the following JSON:

    {"key1":"5","key2":"10"}

However, now some of my key,value entries will have an optional visibility
that I need to put as a nested key value in my map.  Any key,values that
don't have an optional visibility will use the default.  So, for example if
I specify visibilities for key1, and key2, but not key3 I want to get JSON
out that looks like this:

    {"key1":"5",
     "key2":"10",
     "key3":"17",
     "visibility" : { "key1": "a&b&!c", "key2": "a&b", "_default": "a" }
    }

How can I get Camel to marshall a Java object with nested key,value pairs? 
I'm a visual learner, so a simple example would be helpful.

I tried changing my Map to have a value as an object i.e.,:

    Map<String,Object> demoMap = new TreeMap<String,Object>

and then tried adding nested key,values for some keys with an ArrayList
using
http://examples.javacodegeeks.com/core-java/json/jackson/convert-java-map-to-from-json-using-jackson-example/
for reference, but realized that this just gives me a bunch of nested values
under a key, not a bunch of nested key,value pairs.

Even when I tried it for grins, I got an error from the Camel processor with
a java.lang.ClassCastException stating java.util.ArrayList cannot be cast to
java.lang.String

And similarly when I tried to nest a Map inside my demoMap I got this
ClassCastException:

    3244 [hello.world.request.timer] ERROR
org.apache.camel.processor.DefaultErrorHandler  - Failed delivery for
exchangeId: e6518e39-89b7-435e-96d9-ce26811ac67e. Exhausted after delivery
attempt: 1 caught: java.lang.ClassCastException: java.util.HashMap cannot be
cast to java.lang.String

So I know how NOT to do it. :-/

I re-read the Camel JSON documentation at http://camel.apache.org/json.html
but as of this writing it doesn't specify an example with nested key,value
pairs.



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