Accessing jsonpath elements with nested objects

问题:

I am looking to extract certain values from a JSON path of arrays and objects and use these values for further processing and am struggling with accessing those elements. Here is the JSON response:

[  
 {  
  "od_pair":"7015400:8727100",
  "buckets":[  
     {  
        "bucket":"C00",
        "original":2,
        "available":2
     },
     {  
        "bucket":"A01",
        "original":76,
        "available":0
     },
     {  
        "bucket":"B01",
        "original":672,
        "available":480
     }
    ]
    },
 {  
  "od_pair":"7015400:8814001",
  "buckets":[  
     {  
        "bucket":"C00",
        "original":2,
        "available":2
     },
     {  
        "bucket":"A01",
        "original":40,
        "available":40
     },
     {  
        "bucket":"B01",
        "original":672,
        "available":672
     },
     {  
        "bucket":"B03",
        "original":632,
        "available":632
     },
     {  
        "bucket":"B05",
        "original":558,
        "available":558
     }
    ]
 }
]

I tried accessing the root elements with $ but I could not get further with it.

Here is the test method that I have written. I want to extract the value for od_pair and within each od_pair, I need to be able to retrieve the bucket codes and their available numbers.

public static void updateBuckets(String ServiceName, String DateOfJourney) throws Exception {
    File jsonExample = new File(System.getProperty("user.dir"), "\\LogAvResponse\\LogAvResponse.json");
    JsonPath jsonPath = new JsonPath(jsonExample);

    List<Object> LegList = jsonPath.getList("$");
    // List<HashMap<String, String>> jsonObjectsInArray = jsonPath.getList("$");

    int NoofLegs = LegList.size();
    System.out.println("No of legs :" + NoofLegs);
    for (int j = 0; j <= NoofLegs; j++)
    // for (HashMap<String, String> jsonObject : jsonObjectsInArray) {
    {

        String OD_Pair = jsonPath.param("j", j).getString("[j].od_pair");
        // String OD_Pair = jsonObject.get("od_pair");

        System.out.println("OD Pair: " + OD_Pair);
        List<Object> BucketsList = jsonPath.param("j", j).getList("[j].buckets");

        int NoOfBuckets = BucketsList.size();
        // System.out.println("OD Pair: " + OD_Pair);
        System.out.println("no of Buckets: " + NoOfBuckets);

        for (int i = 0; i < NoOfBuckets; i++) {
            String BucketCode = jsonPath.param("j", j).param("i", i).getString("[j].buckets[i].bucket");
            String Available = jsonPath.param("j", j).param("i", i).getString("[j].buckets[i].available");

            int BucketCodeColumn = XLUtils.getBucketCodeColumn(BucketCode);
            int ServiceRow = XLUtils.getServiceRow(ServiceName, DateOfJourney, OD_Pair);
            System.out.println("Row of " + ServiceName + ":" + DateOfJourney + "is:" + ServiceRow);
            System.out.println("Bucket Code column of " + BucketCode + " is: " + BucketCodeColumn);
            XLUtils.updateAvailability(ServiceRow, BucketCodeColumn, Available);
        }
    }

}

}

This is the error I see:

Caused by: 
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup 
failed:
Script1.groovy: 1: unexpected token: [ @ line 1, column 27.
restAssuredJsonRootObject.[j].od_pair

Can someone help me please?

回答1:

I would suggest parsing your JSON into Java classes to ease the processing.

How to do that? First, we need to create Java classes which will represent the JSON you provided.

Let's analyze the JSON. Starts with an array. The array contains multiple JSON Object. These objects contain od_pair value and array of objects called buckets.

Let's create a class (you can name it whatever you want) Pair

public class Pair {
    public String od_pair; //this name is important because it corresponds with the json element's name!
    public List<BucketObject> buckets; //same here!
}

This class represents a single JSON Object in the main Array. It contains od_pair value AND nested JSON Array but in Java representation -> List of BucketObject classes. Let's create BucketObject class:

public class BucketObject { //this name is NOT importnat
    public String bucket; //names are important
    public int original;
    public int available;
}

We have only 3 values in each of the objects.

Now, it's time to parse JSON into the written classes.

JsonPath path = JsonPath.from(json);
Pair[] pairs = path.getObject("$", Pair[].class);

Remember that Pair is a single JSON Object. That's why we start parsing from the root represented by dollar sign $ and we declare that JSON should be parsed into an ARRAY of Pair objects!

Now, processing will be much simpler!

I am not sure what do you need, but I will show you an example of how to get data from the buckets based on od_pair field and you should be able to figure out the rest of the processing.

So, we have the array of Pair class: Pair[] pairs;

Now, we want to get 1 Pair object based on od_pair value.

    public static Pair getPairBasedOnOdPairValue(Pair[] pairs, String odPairValue) {
        for (Pair pair : pairs) {
            if (pair.od_pair.equals(odPairValue)) return pair;
        }

        throw new NoSuchElementException();
    }

Now, we have the Pair object. We can access buckets for this object using

List<BucketObject> buckets = pair.buckets;

The rest of the processing is iterating over List<BucketObject> and getting desired values.

Hope it helps!

回答2:

OP asked me to advise on how to fix his code, hence the second answer.

Let's analyze the code you provided:

public static void updateBuckets(String ServiceName, String DateOfJourney) throws Exception {
    File jsonExample = new File(System.getProperty("user.dir"), "\\LogAvResponse\\LogAvResponse.json");
    JsonPath jsonPath = new JsonPath(jsonExample);

    List<Object> LegList = jsonPath.getList("$");
    // List<HashMap<String, String>> jsonObjectsInArray = jsonPath.getList("$");

    int NoofLegs = LegList.size();
    System.out.println("No of legs :" + NoofLegs);
    for (int j = 0; j <= NoofLegs; j++)
    // for (HashMap<String, String> jsonObject : jsonObjectsInArray) {
    {

        String OD_Pair = jsonPath.param("j", j).getString("[j].od_pair");
        // String OD_Pair = jsonObject.get("od_pair");

        System.out.println("OD Pair: " + OD_Pair);
        List<Object> BucketsList = jsonPath.param("j", j).getList("[j].buckets");

        int NoOfBuckets = BucketsList.size();
        // System.out.println("OD Pair: " + OD_Pair);
        System.out.println("no of Buckets: " + NoOfBuckets);

        for (int i = 0; i < NoOfBuckets; i++) {
            String BucketCode = jsonPath.param("j", j).param("i", i).getString("[j].buckets[i].bucket");
            String Available = jsonPath.param("j", j).param("i", i).getString("[j].buckets[i].available");

            int BucketCodeColumn = XLUtils.getBucketCodeColumn(BucketCode);
            int ServiceRow = XLUtils.getServiceRow(ServiceName, DateOfJourney, OD_Pair);
            System.out.println("Row of " + ServiceName + ":" + DateOfJourney + "is:" + ServiceRow);
            System.out.println("Bucket Code column of " + BucketCode + " is: " + BucketCodeColumn);
            XLUtils.updateAvailability(ServiceRow, BucketCodeColumn, Available);
        }
    }

}

I am not using compilator right now, so I can miss a few things.

#1

First thing I can see is that you save the main array into the List<Object> List<Object> LegList = jsonPath.getList("$");

Instead, you could save it to more understandable type, since Object is so generic, you have no idea what's inside it.

List<HashMap<String, Object>> LegList = jsonPath.getList("$");

#2 The for loop looks incorrect because of the evaluator j <= NoofLegs;. This will probably cause IndexArrayOutOfBoundsException or something similar. With the given code, if you have 4 legs, the for loop will try to process 5 legs which are incorrect.

#3 Similar to the #1, line where you save the bucket list List<Object> BucketsList = jsonPath.param("j", j).getList("[j].buckets"); Could also be changed to List<HashMap<String, Object>> instead.

If you'd do that, you wouldn't need integer-based nested for loop.

You see, the HashMap<String, Object> is actually crucial to parse nested objects. The String is just a name like buckets or od_pair. It's the JSON representation. The second argument Object is different. RestAssured returns different types within the HashMap, that's why we use Object instead of String. Sometimes it's not String.

Example based on your JSON:

Collect buckets to List of HashMaps:

List<HashMap<String, Object>> bucketsList = jsonPath.param("j", j).getList("[j].buckets");

Each of the HashMap in the list is a representation of this:

{  
        "bucket":"C00",
        "original":2,
        "available":2
},

The Object in HashMap is either String or Integer in your case. So, if you get element bucket from a HashMap you'll get its value.

Let's combine it with for loop for further clarification:

List<HashMap<String, Object>> bucketsList = jsonPath.param("j", j).getList("[j].buckets");
for (HashMap<String, Object> singleBucket : bucketsList) {
    String firstValue = (String) singleBucket.get("bucket");
    Integer secondValue = (Integer) singleBucket.get("original");
}

回答3:

Looking at the error message, it looks like you are using rest-assured and that the JsonPath class is io.restassured.path.json.JsonPath from the rest-assured library.

I'm sure you're aware, but (perhaps for other readers) note that this is different from Jayway's json-path and is NOT the com.jayway.jsonpath.JsonPath class from that library.

Also be aware that, as mentioned in the documentation rest-assured uses the Groovy GPath syntax for manipulating/extracting JSON.

With that, I believe the following will extract what you need, i.e. od_pair and their corresponding buckets with available numbers:

Map<String, Map<String, Integer>> map = JsonPath.with(jsonString).get("collectEntries{entry -> [entry.od_pair, entry.buckets.collectEntries{bucketEntry -> [bucketEntry.bucket, bucketEntry.available]}]}");

where for each entry of the map, the key is the od_pair and the value is another map whose key is the bucket and value is the available number. The jsonString is the JSON you provided in the question.

You can iterate through the map to get what you want:

for(Map.Entry<String, Map<String, Integer>> entry : map.entrySet())
{
    String od_pair = entry.getKey();

    Map<String, Integer> bucketMap = entry.getValue();

    for(Map.Entry<String, Integer> bucketEntry : bucketMap.entrySet())
    {
        String bucket = bucketEntry.getKey();
        int available = bucketEntry.getValue();
    }
}

Printing out the map you will get:

{7015400:8727100={C00=2, A01=0, B01=480}, 7015400:8814001={C00=2, A01=40, B01=672, B03=632, B05=558}}

Printing the map as JSON using Gson:

System.out.println(new GsonBuilder().setPrettyPrinting().create().toJson(map));

you will get

{
  "7015400:8727100": {
    "C00": 2,
    "A01": 0,
    "B01": 480
  },
  "7015400:8814001": {
    "C00": 2,
    "A01": 40,
    "B01": 672,
    "B03": 632,
    "B05": 558
  }
}

For background, the String collectEntries{entry -> [entry.od_pair, entry.buckets.collectEntries{bucketEntry -> [bucketEntry.bucket, bucketEntry.available]}]}

is a Groovy closure that uses methods from the Groovy Collections API: Refer Collection, List and Map

Shout out to @Fenio for the pure Java solution above.