JKVC - Key Value Coding for Java data structures

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Description

JKVC is a tool for querying hierarchies of Java collections (currently lists + maps). It's based off of the kvc project.

Status

• Very much a work in progress.
• Error handling
• Once I get things completely tested, I'll release a maven artifact to Maven central.

Example

// setup a demo hash containing lists
HashMap<String, List<Integer>> m = new HashMap<String, List<Integer>>();
List<Integer> a = new ArrayList<Integer>();
a.add(100);
a.add(200);
a.add(300);

List<Integer> b = new ArrayList<Integer>();
b.add(111);
b.add(222);
b.add(333);

m.put("foo", a);
m.put("bar", b);

// get the value of foo from m
assertEquals("[100, 200, 300]", JKVC.prepare("foo").eval(m).toString());

// get the value of foo from m, get it's "1th" element (starting from 0)
assertEquals(200, JKVC.prepare("foo.@i[1]").eval(m));

// get the value of foo from m, call the @count aggregate function on the list
assertEquals(3l, JKVC.prepare("foo.@count").eval(m));

// get the value of foo from m, call the .size() Java method
assertEquals(3, JKVC.prepare("foo.#size").eval(m));

// get the value of foo from m, call the @sum aggregate function on the list
assertEquals(600.0d, JKVC.prepare("foo.@sum").eval(m));

// get the value of foo from m, get it's first element (starting from 0)
assertEquals(111, JKVC.prepare("bar.@i[0]").eval(m));

Querying JSON

Pass a JKVCJsonEvalFactory into each call to JKVC.prepare:

String testData = 
"{\n" +
"    \"firstName\": \"John\",\n" +
"    \"lastName\": \"Smith\",\n" +
"    \"age\": 25,\n" +
"    \"address\": {\n" +
"        \"streetAddress\": \"21 2nd Street\",\n" +
"        \"city\": \"New York\",\n" +
"        \"state\": \"NY\",\n" +
"        \"postalCode\": 10021\n" +
"    },\n" +
"    \"phoneNumbers\": [\n" +
"        {\n" +
"            \"type\": \"home\",\n" +
"            \"number\": \"212 555-1234\"\n" +
"        },\n" +
"        {\n" +
"            \"type\": \"fax\",\n" +
"            \"number\": \"646 555-4567\"\n" +
"        }\n" +
"    ]\n" +
"}";
ObjectMapper mapper = new ObjectMapper();
JsonNode rootNode = mapper.readValue(testData, JsonNode.class);
JKVCJsonEvalFactory f = new JKVCJsonEvalFactory();
System.out.println(JKVC.prepare("firstName",f).eval(rootNode));
System.out.println(JKVC.prepare("lastName", f).eval(rootNode));
System.out.println(JKVC.prepare("address.postalCode",f).eval(rootNode));
System.out.println(JKVC.prepare("phoneNumbers.@count", f).eval(rootNode));
System.out.println(JKVC.prepare("phoneNumbers.@i[1].number", f).eval(rootNode));

will yield:

"John"
"Smith"
10021
2
"646 555-4567"

TODO: look into possible quoting problem

Customizing

A developer can supply their own JKVCEvalFactory to the JKVC.prepare() method to traverse and evaluate an object hierarchy.

Custom aggregation functions can be supplied by adding a function_name (as a String), JKVCAggregate impl to JKVCEvalAggregate.aggregateFunctions().

Contributing

Fork this repo, create a feature branch using something like this:

git checkout -b branch_name

and submit a pull request.

Please send me an email (dparfitt at basho dot com) and let me know if you want to work on any features.

Only friendly pull requests accepted.

#License

http://www.apache.org/licenses/LICENSE-2.0.html

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© 2013 Dave Parfitt