JSON conversion to a specific format - json

Question

I have a Java Object and trying to convert this to a specific JSON format
public class Audit {
String auditId;
String auditData;
}
and above object needs to convert to below JSON format
{
"event":"auditId=100,auditData=purchase order"
}
how do we convert above format using Jackson parser

Answer 1

You need to write a custom serializer for Audit class.
public class AuditSerializer extends StdSerializer<Audit> {
public AuditSerializer() {
super(Audit.class);
}
protected AuditSerializer(Class<Audit> auditClass) {
super(auditClass);
}
#Override
public void serialize(Audit audit, JsonGenerator gen, SerializerProvider provider) throws IOException {
gen.writeStartObject();
String key = "event";
String value = String.format("auditId=%s,auditData=%s", audit.auditId, audit.auditData);
gen.writeStringField(key, value);
gen.writeEndObject();
}
}
And then use this custom serializer to get JSON string for Audit:
SimpleModule module = new SimpleModule();
module.addSerializer(new AuditSerializer(Audit.class));
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(module);
Audit audit = new Audit();
audit.auditId = "100";
audit.auditData = "purchase Order";
System.out.println(mapper.writeValueAsString(audit));
// {"event":"auditId=100,auditData=purchase Order"}
If you annotate Audit class with #JsonSerialize(using=AuditSerializer.class), then you do not need to explicitly register AuditSerializer.
#JsonSerialize(using=AuditSerializer.class)
public class Audit {
...
And you use ObjectMapper directly.
Audit audit = new Audit();
audit.auditId = "100";
audit.auditData = "purchase Order";
ObjectMapper mapper = new ObjectMapper();
System.out.println(mapper.writeValueAsString(audit));
// {"event":"auditId=100,auditData=purchase Order"}