Searching in a Complex Data structure using Java Streams

Question

[
 {"productStatus":
    [
     {"status": "spoilt"},
     {"status": "used"}
    ],
 "productMsg":
    [
    {"msg": "Valid"}
    ]
 },
 {"productStatus":
    [
     {"status": "new"},
    ],
 "productMsg":
    [
    {"msg": "Ok"},
    {"customMsg" : "blah blah"}
    ]
 }
]

I have the above data stored in a List<Map<String, List<Map<String, String>>>>;

For example:

val is represented by Lombok library.
val firstObj = ImmutableList.of(ImmutableMap.of("status", "spoilt"),
                ImmutableMap.of("status", "new"),
                ImmutableMap.of("status", "used"));
val secondObj = ImmutableList.of(ImmutableMap.of("msg", "Valid"));
val productStatus1 = ImmutableMap.of("productStatus", firstObj,
                "productMsg", secondObj);

val firstObj_1 = ImmutableList.of(ImmutableMap.of("status", "new"));
val secondObj_2 = ImmutableList.of(ImmutableMap.of("msg", "Ok"));
val productStatus_2 = ImmutableMap.of("productStatus", firstObj_1,
                "productMsg", secondObj_2);

val testObj = ImmutableList.of(productStatus1, productStatus_2);

I need to find out if a productStatus is new, then get all the productMsgs. For example in the example I gave: I will be requiring the map of

{"msg": "Ok"},
{"customMsg" : "blah blah"}

For every productStatus which has a status new, keep adding it to a list. Basically I will need to return a List<Map<String, String>>.

I know how I can go about doing this in a traditional Java for loop method, which I feel is just too clumsy and long. Is there a neat way to do this using Streams?

@GhostCat As mentioned I am using Lombok for val. You should check it out. Can make programming much faster! — user1692342, Aug 30 '17 at 06:27
I know plain old java object..but wanted to understand context — user1692342, Aug 30 '17 at 06:29
You should create classes for your data instead of storing everything as lists of maps of strings. It'll make your life (and ours) much easier. — shmosel, Aug 30 '17 at 06:29
@shmosel yes, but unfortunately, this is the data I receive from a library. I cant change the format. — user1692342, Aug 30 '17 at 06:30
Are you suggesting me to parse the data first and store it in a class and then do whatever search i requre ? — user1692342, Aug 30 '17 at 06:32
I guess it depends how you're using the data and how long it will stick around, but it's definitely worth considering. — shmosel, Aug 30 '17 at 06:33
Back to your question, why isn't the first item in the result, if it has a `{"status": "new"}`? — shmosel, Aug 30 '17 at 06:33
Well I will be requiring just the output and then I can wont need the object again — user1692342, Aug 30 '17 at 06:34
@shmosel yes it should be there. I will remove the new. My bad — user1692342, Aug 30 '17 at 06:35
Maybe better to use a library and look for in the json instead load all to the difficult structure of lists and maps. [How to search/find In JSON with java](https://stackoverflow.com/questions/28982412/how-to-search-find-in-json-with-java) — HAYMbl4, Aug 30 '17 at 06:50

shmosel · Accepted Answer · 2017-08-30T07:03:08.890

2

Untested, but I think this will do what you want:

List<Map<String, String>> msgs = testObj.stream()
        .filter(obj -> obj.get("productStatus").stream()
                .anyMatch(s -> s.get("status").equals("new")))
        .flatMap(obj -> obj.get("productMsg").stream())
        .collect(Collectors.toList());

edited Aug 30 '17 at 07:03

answered Aug 30 '17 at 06:41

shmosel

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Wow! This looks so much neater and shorter :o – user1692342 Aug 30 '17 at 06:46

Searching in a Complex Data structure using Java Streams

1 Answers1