How to display Blob /Json data field in Liferay 7.2? - json

Question

I am using a service builder that is retrieving the form data fine from mysql db. I have a field that has the json data and I tried to map it using object mapper and using com.fasterxml.jackson.databind.ObjectMapper to display the json content. However, the Blob Data is shown as: com.mysql.cj.jdbc.Blob#4ca74f7f
How do I actually get/extract the data from the storing link above? Here is my code snippet:
for (ddmcontent MyTemp : myList) {
System.out.println("Content ID : "+myList.getContentId());
System.out.println("User Blob Data : "+myList.getData());
Blob responseBody =myList.getData();
ObjectMapper objectMapper = new ObjectMapper();
List<ModelData> myDat = objectMapper.readValue((DataInput)
responseBody,objectMapper.getTypeFactory().constructCollectionType
(List.class,ModelData.class));
for (ModelData dt : myDat) {
System.out.println("User Name : "+dt.Name);
System.out.println("Users Email : "+dt.Email);
}
}
Please note, I have defined my ModelData elements as all String.
Any suggestion? What am I missing?
Thanks in advance!

Answer 1

The toString() representation hints at the object's type com.mysql.cj.jdbc.Blob. If you look up its javadoc (or the interface it implements) you'll see the options that you have to decode the contents of the Blob, namely getting an InputStream or a byte[] representation, which you'd have to subject to the correct character set decoding to turn it into a String.
Make sure you nail the character set by testing it with all kinds of Unicode content, so that you don't have to fix badly encoded database content later when your table contains a lot of data in unknown encodings.
As you're using Liferay's Service Builder, you might want to share the relevant parts of your service.xml (optional model-hints.xml) to check for an easier implementation.

Answer 2

I finally got this working by changing the field in question to String and addining a max length to certain number of Char
Thanks!