How to create an item reader which reads a JSON object and array of object inside the main object?

Question

I am creating a spring batch app which accepts a filename from JobParameters and use it to read a json file in a certain path.

I tried creating a JsonItemReader, here is the below code...

@Bean
@StepScope
public JsonItemReader<MyObject> myJsonItemReader() {

    final ObjectMapper mapper = new ObjectMapper();

    final JacksonJsonObjectReader<MyObject> jsonObjectReader = new JacksonJsonObjectReader<>(
            MyObject.class);
    jsonObjectReader.setMapper(mapper);

    final String filePath = config.getRootfolder() + "/" + inputInfo.getFileName();

    return new JsonItemReaderBuilder<MyObject>().jsonObjectReader(jsonObjectReader)
            .resource(new FileSystemResource(filePath))
            .name("myJsonItemReader")
            .build();

}

And here is the sample json i am going to read.

   {                                                                                                
        "attr1":"abc",                                                                                          
        "list":[                                                                                            
            {                                                                                       
                "attr_list1": "abc",                                                                                    
                "attr_list2":"abc"                                                                                                                                                  
            },                                                                                      
            {                                                                                       
                "attr_list1": "abc",                                                                                    
                "attr_list2":"abc",                                                                                                                                                                 
            }                                                                                       
        ]   
    }

But upon running and debugging my reader, i got an error "The Json input stream must start with an array of objects"

Mahmoud Ben Hassine · Accepted Answer · 2021-04-01 08:06:52Z

2

The JsonItemReader expects an array of JSON objects as input, as mentioned in its Javadoc:

ItemStreamReader implementation that reads Json objects from a Resource having
the following format:

[ { // JSON object }, { // JSON object } ]

Your input is not conform to the expected format, so you need to adapt your input or use another item reader.

I would like to mention that a single json object is not suitable to use as input to a batch process. I believe the input should be an array of objects so that the item reader returns items one by one as designed to work with the chunk-oriented processing model offered by Spring Batch (and other frameworks/tools). The ndjson is also a good choice, but certainly not a single object.

answered Apr 1, 2021 at 8:06

Mahmoud Ben Hassine

32.1k5 gold badges38 silver badges67 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

chickenempanada Over a year ago

Thanks for the response, as for the single json object (it is my clients decision) but what i did was pass the json objects not included in the list as JobParameter and i write the array of json object in a json file and read it using JsonItemReader.

Mahmoud Ben Hassine Over a year ago

ok if you found a solution to adapt the input, that's fine.

Collectives™ on Stack Overflow

How to create an item reader which reads a JSON object and array of object inside the main object?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related