Split JSON objects in array string using regex

Question

I have a String in the following format:

[{"HostName":"taskmanager1","Rack":"/default-rack","State":"RUNNING","NodeId":"taskmanager1:45454","NodeHTTPAddress":"taskmanager1:8042","LastHealthUpdate":1519568501615,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},{"HostName":"datanode2","Rack":"/default-rack","State":"RUNNING","NodeId":"datanode2:45454","NodeHTTPAddress":"datanode2:8042","LastHealthUpdate":1519260876106,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},{"HostName":"taskmanager3","Rack":"/default-rack","State":"RUNNING","NodeId":"taskmanager3:45454","NodeHTTPAddress":"taskmanager3:8042","LastHealthUpdate":1519568502251,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},{"HostName":"datanode3","Rack":"/default-rack","State":"RUNNING","NodeId":"datanode3:45454","NodeHTTPAddress":"datanode3:8042","LastHealthUpdate":1519260871527,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},{"HostName":"taskmanager2","Rack":"/default-rack","State":"RUNNING","NodeId":"taskmanager2:45454","NodeHTTPAddress":"taskmanager2:8042","LastHealthUpdate":1519568502259,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},{"HostName":"datanode1","Rack":"/default-rack","State":"RUNNING","NodeId":"datanode1:45454","NodeHTTPAddress":"datanode1:8042","LastHealthUpdate":1519260875647,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024}]

I want to split it into multiple (here 6) JSON format, but my pattern cannot split that as desired.

I want something like this:

{"HostName":"taskmanager1","Rack":"/default-rack","State":"RUNNING","NodeId":"taskmanager1:45454","NodeHTTPAddress":"taskmanager1:8042","LastHealthUpdate":1519568501615,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},
{"HostName":"datanode2","Rack":"/default-rack","State":"RUNNING","NodeId":"datanode2:45454","NodeHTTPAddress":"datanode2:8042","LastHealthUpdate":1519260876106,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},
{"HostName":"taskmanager3","Rack":"/default-rack","State":"RUNNING","NodeId":"taskmanager3:45454","NodeHTTPAddress":"taskmanager3:8042","LastHealthUpdate":1519568502251,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},
{"HostName":"datanode3","Rack":"/default-rack","State":"RUNNING","NodeId":"datanode3:45454","NodeHTTPAddress":"datanode3:8042","LastHealthUpdate":1519260871527,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024}
,{"HostName":"taskmanager2","Rack":"/default-rack","State":"RUNNING","NodeId":"taskmanager2:45454","NodeHTTPAddress":"taskmanager2:8042","LastHealthUpdate":1519568502259,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024},
{"HostName":"datanode1","Rack":"/default-rack","State":"RUNNING","NodeId":"datanode1:45454","NodeHTTPAddress":"datanode1:8042","LastHealthUpdate":1519260875647,"HealthReport":"","NodeManagerVersion":"2.8.3","NumContainers":0,"UsedMemoryMB":0,"AvailableMemoryMB":1024}

Using the code:

List<String> res = Arrays.asList(temp.replace('[', ' ').replace(']',' ').trim()).split(",");

It will be split for every , character and using the pattern split("},\\}") will remove } and { character, too.

How can I split that as desire to make Json objects?

Using the Java pattern (\\{.+}) will group whole string.

Can you please show the code you tried? And the errors you got? — OneCricketeer
– OneCricketeer, Commented Feb 25, 2018 at 15:13
And you don't really need an explicit JsonObject, you only need the jsonarray class — OneCricketeer
– OneCricketeer, Commented Feb 25, 2018 at 15:14
you know, because it's a String, It can't be parsed as JSONArray and because it is not nested JSON it can't be parsed as JSONObject! — Soheil Pourbafrani
– Soheil Pourbafrani, Commented Feb 25, 2018 at 15:17

D.B. · Accepted Answer · 2018-02-25 15:38:21Z

You can parse the JSON as an array and treat the contents as individual strings. Here is sample code:

import org.json.JSONArray;

public class orgJson1Main {
    private static final String sample = "[{\"HostName\":\"taskmanager1\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"taskmanager1:45454\",\"NodeHTTPAddress\":\"taskmanager1:8042\",\"LastHealthUpdate\":1519568501615,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"datanode2\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"datanode2:45454\",\"NodeHTTPAddress\":\"datanode2:8042\",\"LastHealthUpdate\":1519260876106,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"taskmanager3\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"taskmanager3:45454\",\"NodeHTTPAddress\":\"taskmanager3:8042\",\"LastHealthUpdate\":1519568502251,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"datanode3\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"datanode3:45454\",\"NodeHTTPAddress\":\"datanode3:8042\",\"LastHealthUpdate\":1519260871527,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"taskmanager2\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"taskmanager2:45454\",\"NodeHTTPAddress\":\"taskmanager2:8042\",\"LastHealthUpdate\":1519568502259,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"datanode1\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"datanode1:45454\",\"NodeHTTPAddress\":\"datanode1:8042\",\"LastHealthUpdate\":1519260875647,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024}]";

    public static void main(String[] args) {
        JSONArray array = new JSONArray(sample);
        for(int i=0; i < array.length(); i++){
            System.out.println(array.get(i));
        }
    }

}

OUTPUT:

{"NodeManagerVersion":"2.8.3","Rack":"/default-rack","LastHealthUpdate":1519568501615,"HealthReport":"","State":"RUNNING","AvailableMemoryMB":1024,"NodeId":"taskmanager1:45454","UsedMemoryMB":0,"NodeHTTPAddress":"taskmanager1:8042","HostName":"taskmanager1","NumContainers":0}
{"NodeManagerVersion":"2.8.3","Rack":"/default-rack","LastHealthUpdate":1519260876106,"HealthReport":"","State":"RUNNING","AvailableMemoryMB":1024,"NodeId":"datanode2:45454","UsedMemoryMB":0,"NodeHTTPAddress":"datanode2:8042","HostName":"datanode2","NumContainers":0}
{"NodeManagerVersion":"2.8.3","Rack":"/default-rack","LastHealthUpdate":1519568502251,"HealthReport":"","State":"RUNNING","AvailableMemoryMB":1024,"NodeId":"taskmanager3:45454","UsedMemoryMB":0,"NodeHTTPAddress":"taskmanager3:8042","HostName":"taskmanager3","NumContainers":0}
{"NodeManagerVersion":"2.8.3","Rack":"/default-rack","LastHealthUpdate":1519260871527,"HealthReport":"","State":"RUNNING","AvailableMemoryMB":1024,"NodeId":"datanode3:45454","UsedMemoryMB":0,"NodeHTTPAddress":"datanode3:8042","HostName":"datanode3","NumContainers":0}
{"NodeManagerVersion":"2.8.3","Rack":"/default-rack","LastHealthUpdate":1519568502259,"HealthReport":"","State":"RUNNING","AvailableMemoryMB":1024,"NodeId":"taskmanager2:45454","UsedMemoryMB":0,"NodeHTTPAddress":"taskmanager2:8042","HostName":"taskmanager2","NumContainers":0}
{"NodeManagerVersion":"2.8.3","Rack":"/default-rack","LastHealthUpdate":1519260875647,"HealthReport":"","State":"RUNNING","AvailableMemoryMB":1024,"NodeId":"datanode1:45454","UsedMemoryMB":0,"NodeHTTPAddress":"datanode1:8042","HostName":"datanode1","NumContainers":0}

EDIT:

First, I removed the JSONTokener from the above code. Second, for completeness I'm adding the following code that shows how to find the individual JSON objects within the sample string using a regex as originally asked.

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class orgJson1Main {
    private static final String sample = "[{\"HostName\":\"taskmanager1\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"taskmanager1:45454\",\"NodeHTTPAddress\":\"taskmanager1:8042\",\"LastHealthUpdate\":1519568501615,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"datanode2\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"datanode2:45454\",\"NodeHTTPAddress\":\"datanode2:8042\",\"LastHealthUpdate\":1519260876106,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"taskmanager3\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"taskmanager3:45454\",\"NodeHTTPAddress\":\"taskmanager3:8042\",\"LastHealthUpdate\":1519568502251,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"datanode3\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"datanode3:45454\",\"NodeHTTPAddress\":\"datanode3:8042\",\"LastHealthUpdate\":1519260871527,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"taskmanager2\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"taskmanager2:45454\",\"NodeHTTPAddress\":\"taskmanager2:8042\",\"LastHealthUpdate\":1519568502259,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024},{\"HostName\":\"datanode1\",\"Rack\":\"/default-rack\",\"State\":\"RUNNING\",\"NodeId\":\"datanode1:45454\",\"NodeHTTPAddress\":\"datanode1:8042\",\"LastHealthUpdate\":1519260875647,\"HealthReport\":\"\",\"NodeManagerVersion\":\"2.8.3\",\"NumContainers\":0,\"UsedMemoryMB\":0,\"AvailableMemoryMB\":1024}]";

    public static void main(String[] args) {

        Matcher matcher = Pattern.compile("\\{[^}]*\\}").matcher(sample);
        while(matcher.find()){
            System.out.println(matcher.group());
        }
    }

}

Tokener isn't needed stleary.github.io/JSON-java/org/json/…
Good catch @cricket_007 I don't often use the JSON-java library to parse and I forgot about that.

Bohemian · Accepted Answer · 2018-02-25 15:23:30Z

2

To split on }, {, but retain the curly brackets in the tokens, split on this regex:

"(?<=\\}), (?=\\{)"

Which uses a look behind and a look ahead to assert the curly brackets preceed and follow the comma, but not consume them in the split.

The whole line then becomes:

List<String> res = Arrays.asList(temp.replaceAll("^.|.$", "").split("(?<=\\}), (?=\\{)");

Note also the simplified trimming of leading [ and trailing ] but more-simply removing the first and last character in one operation.

answered Feb 25, 2018 at 15:23

Bohemian♦

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Comments

Srdjan M. · Accepted Answer · 2018-02-25 16:47:36Z

If your purpose to use this List as list of MyJsonObject I would recommend to reuse brilliant google gson library. There is easy way to convert String to List without intermediate manipulation with List. What you need to follow followed steps.

1) Create your POJO class:

public class POJO 
{
    String HostName;
    String Rack;
    String State;
    String NodeId;
    String NodeHTTPAddress;
    String LastHealthUpdate;
    String HealthReport;
    String NodeManagerVersion;
    String NumContainers;
    String UsedMemoryMB;
    String AvailableMemoryMB;
    ... getters/setters here ....
}

2) Create gson converter:

Gson gson = (new GsonBuilder() ).create();

3) Create typeToken for list of your POJOs:

 Type type = new TypeToken< List<POJO> >(){}.getType();

4) Convert String to desire collection:

 List<MyJsonObject> list = gson.fromJson( json, type );

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